Composite material including alumina short fibers as reinforcing material and aluminium alloy with copper and magnesium as matrix metal

Abstract

 A composite material is made from alumina short fibers embedded in a matrix of metal. The fiber volume proportion of the alumina short fibers is between approximately 5% and approximately 50%. The metal is an alloy consisting essentially of between approximately 2% and approximately 6% of copper, between approximately 0.5% and approximately 4% of magnesium, and remainder substantially aluminum. The fibervolume proportion of the alumina shortfibers may more desirably be between approximately 5% and approximately 40%; the magnesium content of the aluminum alloy matrix metal may more desirably be between approximately 2% and approximately 4%; and desirably the fiber volume proportion of the alumina short fibers may be between approximately 5% and approximately 20%, when the copper content of the aluminum alloy matrix metal should desirably be between approximately 3% and approximately 6%; or alternatively desirably the fiber volume proportion of the alumina short fibers may be between approximately 30% and approximately 40%, when the copper content ofthe aluminum alloy matrix. metal should desirably be between approximately 2% and approximately 5%.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a composite material made up from reinforcing fibers embedded in a matrix of metal, and more particularly relates to such a composite material utilizing alumina short fiber material as the reinforcing fiber material and aluminum alloy as the matrix metal.

[0002] The present patent application has been at least partly prepared utilizing materials which were disclosed in Japanese Patent Application Serial No. 60-120787 (₁₉₈₅), laid open as Japanese Patent Laying Open Publication Serial No. ............................ (1986), and the present patent application hereby incorporates into itself by reference the disclosure of said Japanese Patent Application and of the claims and of the drawings thereof; a copy of said Japanese Patent Application is appended to this application.

[0003] In the prior art, the following aluminum alloys have been utilized as matrix metal for a composite material:

Cast type aluminum alloys

JIS standard AC8A (0.8 to 1.3% Cu, 11.0 to 13.0% Si, 0.7 to 1.3% Mq, 0.8 to 1.5% Ni, remainder substantially Al)

JIS standard AC8B (2.0 to 4.0% Cu, 8.5 to 10.5% Si, 0.5 to 1.5% Mg, 0.1 to 1% Ni, remainder substantially Al)

JIS standard AC4C (Not more than 0.25% Cu, 6.5 to 7.5% Si, 0.25 to 0.45% Mg, remainder substantially Al)

AA standard A201 (4 to 5% Cu, 0.2 to 0.4% Mn, 0.15 to 0.35% Mg, 0.15 to 0.35% Ti, remainder substantially Al)

AA standard A356 (6.5 to 7.5% Si, 0.25 to 0.45% Mg, not more than 0.2 Fe, not more than 0.2% Cu, remainder substantially Al)

Al - 2 to 3% Li alloy (DuPont)

Wrought type aluminum alloys

JIS standard 6061 (0.4 to 0.8% Si, 0.15 to 0.4% Cu, 0.8 to 1.2% Mg, 0.04 to 0.35% Cr, remainder substantially Al)

JIS standard 5056 (not more than 0.3% Si, not more than 0.4% Fe, not more than 0.1% Cu, 0.05 to 0.2% Mn, 4.5 to 5.6% Mg, 0.05 to 0.2% Cr, not more than 0.1% Zn, remainder substantially Al)

JIS standard 2024 (0.5% Si, 0.5% Fe, 3.8 to 4.9% Cu, 0.3 to 0.9% Mn, 1.2 to 1.8% Mg, not more than 0.1% Cr, not more than 0.25% Zn, not more than 0.15% Ti, remainder substantially Al)

JIS standard 7075 (not more than 0.4% Si, not more than 0.5% Fe, 1.2 to 2.0% Cu, not more than 0.3 Mn, 2.1 to 2.9% Mg, 0.18 to 0.28% Cr, 5.1 to 6.1% Zn, 0.2% Ti, remainder substantially Al)

[0004] Previous research relating to composite materials incorporating aluminum alloys as their matrix metals has generally been carried out from the point of view and with the object of improving the strength and so forth of existing aluminum alloys, and therefore these aluminum alloys conventionally used in the manufacture of such prior art composite materials have not necessarily been of the optimum composition in relation to the type of reinforcing fibers utilized therewith to form a composite material, and therefore, in the case of using such conventional above mentioned aluminum alloys as the matrix metal for a composite material, it has not heretofore been attained to optimize the mechanical characteristics, and particularly the strength, of the composite materials using such aluminum alloys as matrix metal.

SUMMARY OF THE INVENTION

[0005] The inventors of the present application have considered the above mentioned problems in composite materials which use such conventional aluminum alloys as matrix metal, and in particular have considered the particular case of a composite material which utilizes alumina short fibers as reinforcing fibers; since such. alumina short fibers, of the various reinforcing fibers used conventionally in the manufacture of a fiber reinforced metal composite material, have particularly high strength, and are exceedingly effective in improving the high temperature stability and strength. And the present inventors, as a result of various experimental researches performed in order to determine what composition of the aluminum alloy to be used as the matrix metal for such a composite material is optimum, have discovered that an aluminum alloy having a content of copper and magnesium within certain limits, and containing substantially no silicon, nickel, zinc, and so forth is optimal as matrix metal. The present invention is based on the knowledge obtained from the results of the various experimental researches carried out by the inventors of the present application, as will be detailed later in this specification.

[0006] Accordingly, it is the primary object of the present invention to provide a composite material utilizing alumina short fibers as reinforcing material and aluminum alloy as matrix metal, which enjoys superior mechanical characteristics such as bending strength.

[0007] It is a further object of the present invention to provide such a composite material utilizing alumina short fibers as reinforcing material and aluminum alloy as matrix metal, which is cheap.

[0008] It is a further object of the present invention to provide such a composite material utilizing alumina short fibers as reinforcing material and aluminum alloy as matrix metal, which, for similar values of mechanical characteristics such as bending strength, can incorporate a lower volume proportion of reinforcing fiber material than prior art such composite materials.

[0009] It is a further object of the present invention to provide such a composite material utilizing alumina short fibers as reinforcing material and aluminum alloy as matrix metal, which is improved over prior art such composite materials as regards machinability.

[0010] It is a further object of the present invention to provide such a composite material utilizing alumina short fibers as reinforcing material and aluminum alloy as matrix metal, which is improved over prior art such composite materials as regards workability.

[0011] It is a further object of the present invention to provide such a composite material utilizing alumina short fibers as reinforcing material and aluminum alloy as matrix metal, which has good characteristics with regard to amount of wear on a mating member.

[0012] It is a yet further object of the present invention to provide such a composite material utilizing alumina short fibers as reinforcing material and aluminum alloy as matrix metal, which is not brittle.

[0013] It is a yet further object of the present invention to provide such a composite material utilizing alumina short fibers as reinforcing material and aluminum alloy as matrix metal, which is durable.

[0014] It is a yet further object of the present invention to provide such a composite material utilizing alumina short fibers as reinforcing material and aluminum alloy as matrix metal, which has good wear resistance.

[0015] It is a yet further object of the present invention to provide such a composite material utilizing alumina short fibers as reinforcing material and aluminum alloy as matrix metal, which has good uniformity.

[0016] According to the most general aspect of the present invention, these and other objects are accomplished by a composite material, comprising alumina short fibers embedded in a matrix of metal, the fiber volume proportion of said alumina short fibers being between approximately 5% and approximately 50%, and said metal being an alloy consisting essentially of between approximately 2% to approximately 6% of copper, between approximately 0.5% to approximately 4% of magnesium, and remainder substantially aluminum; and more preferably the fiber volume proportion of said alumina short fibers may be between approximately 5% and approximately 40%; more preferably the magnesium content of said aluminum alloy matrix metal may be between approximately 2% and approximately 4%; more preferably the fiber volume proportion of said alumina short fibers may be between approximately 5% and approximately 20%, in which case the copper content of said aluminum alloy matrix metal should be between approximately 3% and approximately 6%; or alternatively the fiber volume proportion of said alumina short fibers should be between approximately 30% and approximately 40%, in which case the copper content of said aluminum alloy matrix metal should be between approximately 2% and approximately 5%.

[0017] According to the present invention as described above, as reinforcing fibers there are used alumina short fibers which have high strength, and are exceedingly effective in improving the high temperature stability and strength of the resulting composite material, and as matrix metal there is used an aluminum alloy with a copper content of 2% to 6%, a magnesium content of 0.5% to 4%, and the remainder substantially aluminum, and the volume proportion of the alumina short fibers is from 5% to 50%, whereby, as is clear from the results of experimental research carried out by the inventors of the present application as will be described below, a composite material with superior mechanical characteristics such as strength can be obtained.

[0018] Also according to the present invention, in cases where it is satisfactory if the same degree of strength as a conventional alumina short fiber reinforced aluminum alloy is obtained, the volume proportion of alumina short fibers in a composite material according to the present invention may be set to be lower than the value required for such a conventional composite material, and therefore, since it is possible to reduce the amount of alumina short fibers used, the machinability and workability of the composite material can be improved, and it is also possible to reduce the cost of the composite material. Further, the characteristics with regard to wear on a mating member will be improved.

[0019] As will become clear from the experimental results detailed hereinafter, when copper is added to aluminum to make the matrix metal of the composite material according to the present invention, the strength of the aluminum alloy matrix metal is increased and thereby the strength of the composite material is improved, but that effect is not sufficient if the copper content is less than 2%, whereas if the copper content is more than 6% the composite material becomes very brittle, and has a tendency to rapidly disintegrate. Therefore the copper content of the aluminum alloy used as matrix metal in the composite material of the present invention is required to be in the range of from approximately 2% to approximately 6%, and preferably is required to be in the range of from approximately 3% to approximately 5%.

[0020] Furthermore, oxide radicals are normally present on the surface of such alumina short fibers used as reinforcing fibers, before they are incorporated into the composite material, and if magnesium, which has a strong tendency to form oxides, is included in the molten matrix metal, then it is considered by the present inventors that the magnesium will react with the oxide radicals on the surface of the alumina short fibers during the process of infiltrating the molten matrix metal into the interstices of the reinforcing alumina short fiber mass, and this magnesium will reduce the surface of the alumina short fibers, as a result of which the affinity of the molten aluminum alloy matrix metal and the alumina short fibers will be improved, and by this means the strength of the composite,material will be improved. If, however, the magnesium content is less than 0.5%, as will become clear from the experimental researches given hereinafter, this effect is not sufficient, whereas if the magnesium content is more than 4% it is considered by the present inventors that an excessive oxidation-reduction reaction occurs, and as a result the alumina short fibers deteriorate, or brittle interface reaction products are produced on the surface of the alumina short fibers, and therefore the strength of the composite material is in the end reduced. Therefore the magnesium content of the aluminum alloy used as matrix metal in the composite material of the present invention is required to be in the range of from approximately 0.5% to approximately 4%, and preferably is required to be in the range of from approximately 2% to approximately 4%.

[0021] Furthermore, in a composite material with an aluminum alloy of the above composition as matrix metal, as also will become clear from the experimental researches given hereinafter, if the volume proportion of the alumina short fibers is less than 5%, a sufficient strength cannot be obtained, and if the volume proportion of alumina short fibers exceeds 40% and particularly if it exceeds 50% even if the volume proportion of the alumina short fibers is increased, the strength of the composite material is not very significantly improved. Also, the wear resistance of the composite material increases with the volume proportion of the alumina short fibers, but when the volume proportion of the alumina short fibers is in the range from zero to approximately 5% said wear resistance increases rapidly with an increase in the volume proportion of the alumina short fibers, whereas when the volume proportion of the alumina short fibers is in the range of at least approximately 5%, the wear resistance of the composite material does not very significantly increase with an increase in the volume proportion of said alumina short fibers. Therefore, according to one characteristic of the present invention, the volume proportion of the alumina short fibers is required to be in the range of from approximately 5% to approximately 50%, and preferably is required to be in the range of from approximately 5% to approximately 40%.

[0022] Furthermore, as will become clear from the experimental researches performed by the inventors of the present invention and given hereinafter, even when the volume proportion of the alumina short fibers and the magnesium content are within the above specified limits, the preferable range for the copper content varies slightly depending upon the volume proportion of the alumina short fibers. Therefore, according to another detailed characteristic of the present invention, when the fiber volume proportion of the alumina short fibers is in the range of from about 5% to about 20%, the copper content is desirably required to be in the range of from about 3% to about 6%, whereas, on the other hand, when the fiber volume proportion of the alumina short fibers is in the range of from about 30% to about 40%, the copper content is desirably required to be in the range of from about 2% to about 5%.

[0023] If, furthermore, the copper content of the aluminum alloy used as matrix metal of the composite material of the present invention has a relatively high value, if there are unevennesses in the concentration of the copper within the aluminum alloy, the portions where the copper concentration is high will be brittle, and it will not therefore be possible to obtain a uniform matrix metal or a composite material of good and uniform quality. Therefore, according to another detailed characteristic of the present invention, in order that the concentration of copper within the aluminum alloy matrix metal should be uniform, such a composite material of which the matrix metal is aluminum alloy of which the copper content is at least approximately 2% and is less than approximately 3.5% is subjected to liquidizing processing for from about 2 hours to about 8 hours at a temperature of from about 480°C to about 520°C, and is preferably further subjected to aging processing for about 2 hours to about 8 hours at a temperature of from about 150°C to 200°C, while on the other hand such a composite material of which the matrix metal is aluminum alloy of which the copper content is at least approximately 3.5% and is less than approximately 6.5% is subjected to liquidizing processing for from about 2 hours to about 8 hours at a temperature of from about 460°C to about 510°C, and is preferably further subjected to aging processing for about 2 hours to about 8 hours at a temperature of from about 150°C to 200°C.

[0024] Further the alumina short fibers in the composite material of the present invention may be either alumina alumina non continuous fibers or may be alumina continuous fibers cut to a determinate length. It is also desirable that the composition of the alumina short fibers should be from about 80% to about 100% Al203, remainder substantially Si02, and in this case the crystalline structure of the alumina fibers may be any of the alpha, gamma, and delta crystalline structures. Also, the fiber length of the alumina short fibers is preferably from approximately 10 microns to approximately 7 cm, and particularly is from approximately 10 microns to approximately 5 cm, and the fiber diameter is preferably approximately 1 micron to approximately 30 microns, and particularly is from approximately 1 micron to approximately 25 microns.

[0025] It should be noted that in this specification all percentages, except in the expression of volume proportion of reinforcing fiber material, are percentages by weight, and in expressions of the composition of an aluminum alloy, "substantially aluminum" means that, apart from-aluminum, copper and magnesium, the total of the inevitable metallic elements such as silicon, iron, zinc, manganese, nickel, titanium, and chromium included in the aluminum alloy used as matrix metal is not more than 1%, and each of said elements individually is not present to more than 0.5%. Also, it should be understood that, in the description of the composition of the alumina short fibers, the expression "remainder substantially Si02" means that apart from the A1203 and the Si02 forming the alumina short fibers other substances are present only as impurities. It should further be noted that, in this specification, in descriptions of ranges of compositions, temperatures and the like, the expressions "at least", "not less than", "at most", "no more than", and "from ... to ..." and so on are intended to include the boundary values of the respective ranges.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will now be shown and described with regard to certain of the preferred embodiments thereof, and with reference to the illustrative drawings, which however should not be considered as limitative of the present invention in any way, since the scope of the present invention is to be considered as being delimited solely by the accompanying claims, rather than by any particular features of the disclosed embodiments or of the drawings. In these drawings:

Fig. 1 is a perspective view of a preform made of alumina short fiber material, with said alumina short fibers being aligned-substantially randomly in two dimensions and substantially being stacked in the third dimension, for incorporation into composite materials according to various preferred embodiments of the present invention;

Fig. 2 is a schematic perspective view showing said preform as fitted into a stainless steel case which is shaped as a parallelopiped, ready for a high pressure casting process;

Fig. 3 is a schematic sectional diagram showing a high pressure casting device in the process of performing said high pressure casting process for manufacturing a composite material with the Fig. 1 alumina short fiber material preform incorporated in a matrix of matrix metal;

Fig. 4 is a set of graphs in which copper content in percent is shown along the horizontal axis and bending strength in kg/mm2 is shown along the vertical axis, derived from data relating to bending strength tests for the first set of preferred embodiments of the material of the present invention, each said graph showing the relation between copper content and bending strength of certain composite material test pieces for a particular fixed percentage content of magnesium in the matrix metal of the composite material;

Fig. 5 is a set of graphs in which magnesium content in percent is shown along the horizontal axis and bending strength in kg/mm2 is shown along the vertical axis, derived from data relating to bending strength tests for the first set of preferred embodiments of the material of the present invention, each said graph showing the relation between magnesium content and bending strength of certain composite material test pieces for a particular fixed percentage content of copper in the matrix metal of the composite material;

_Fig. 6 is a set of graphs, similar to Fig. 4 for the first set of preferred embodiments, in which copper content in percent is shown along the horizontal axis and bending strength in kg/mm² is shown along the vertical axis, derived from data relating to bending strength tests for the second set of preferred embodiments of the material of the present invention, each said graph showing the relation between copper content and bending strength of certain composite material test pieces for a particular fixed percentage content of magnesium in the matrix metal of the composite material;

_Fig. 7 is a set of graphs, similar to Fig. 5 for the first set of preferred embodiments, in which magnesium content in percent is shown along the horizontal axis and bending strength in kg/mm² is shown along the vertical axis, derived from data relating to bending strength tests for the second set of preferred embodiments of the material of the present invention, each said graph showing the relation between magnesium content and bending strength of certain composite material test pieces for a particular fixed percentage content of copper in the matrix metal of the composite material;

Fig. 8 is a set of graphs, similar to Figs. 4 and 6 for the first and second sets of preferred embodiments respectively, in which copper content in percent is shown along the horizontal axis and bending strength in kg/mm² is shown along the vertical axis, derived from data relating to bending strength tests for the third set of preferred embodiments of the material of the present invention, each said graph showing the relation between copper content and bending strength of certain composite material test pieces for a particular fixed percentage content of magnesium in the matrix metal of the composite material;

Fig. 9 is a set of graphs, similar to Figs. 5 and 7 for the first and second sets of preferred embodiments respectively, in which magnesium content in percent is shown along the horizontal axis and bending strength in kg/mm² is shown along the vertical axis, derived from data relating to bending strength tests for the third set of preferred embodiments of the material of the present invention, each said graph showing the relation between magnesium content and bending strength of certain composite material test pieces for a particular fixed percentage content of copper in the matrix metal of the composite material;

Fig. 10 is a set of graphs, similar to Figs. 4, 6, and 8 for the first through the third sets of preferred embodiments respectively, in which copper content in percent is shown along the horizontal axis and bending strength in kg/mm² is shown along the vertical axis, derived from data relating to bending strength tests for the fourth set of preferred embodiments of the material of the present invention, each said graph showing the relation between copper content and bending strength of certain composite material test pieces for a particular fixed percentage content of magnesium in the matrix metal of the composite material;

Fig. 11 is a set of graphs, similar to Figs. 5, 7, and 9 for the first through the third sets of preferred embodiments respectively, in which magnesium content in percent is shown along the horizontal axis and bending strength in kg/mm2 is shown along the vertical axis, derived from data relating to bending strength tests for the fourth set of preferred embodiments of the material of the present invention, each said graph showing the relation between magnesium content and bending strength of certain composite material test pieces for a particular fixed percentage content of copper in the matrix metal of the composite material;

Fig. 12 is a set of graphs, similar to Figs. 4, 6, 8 and 10 for the first through the fourth sets of preferred embodiments respectively, in which copper content in percent is shown along the horizontal axis and bending strength in kg/mm2 is shown along the vertical axis, derived from data relating to bending strength tests for the fifth set of preferred embodiments of the material of the present invention, each said graph showing the relation between copper content and bending strength of certain composite material test pieces for a particular fixed percentage content of magnesium in the matrix metal of the composite material;

Fig. 13 is a set of graphs, similar to Figs. 5, 7, 9 and 11 for the first through the fourth sets of preferred embodiments respectively, in which magnesium content in percent is shown along the horizontal axis and bending strength in kg/mm2 is shown along the vertical axis, derived from data relating to bending strength tests for the fifth set of preferred embodiments of the material of the present invention, each said graph showing the relation between magnesium content and bending strength of certain composite material test pieces for a particular fixed percentage content of copper in the matrix metal of the composite material;

Fig. 14 is a set of graphs, similar to Figs. 4, 6, 8, 10 and 12 for the first through the fifth sets of preferred embodiments respectively, in which copper content in percent is shown along the horizontal axis and bending strength in kg/mm² is shown along the vertical axis, derived from data relating to bending strength tests for the sixth set of preferred embodiments of the material of the present invention, each said graph showing the relation between copper content and bending strength of certain composite material test pieces for a particular fixed percentage content of magnesium in the matrix metal of the composite material;

Fig. 15 is a set of graphs, similar to Figs. 5, 7, 9, 11 and 13 for the first through the fifth sets of preferred embodiments respectively, in which magnesium content in percent is shown along the horizontal axis and bending strength in kg/mm² is shown along the vertical axis, derived from data relating to bending strength tests for the sixth set of preferred embodiments of the material of the present invention, each said graph showing the relation between magnesium content and bending strength of certain composite material test pieces for a particular fixed percentage content of copper in the matrix metal of the composite material; and:

Fig. 16 is a graph in which the volume proportion of the reinforcing alumina short fiber material in percent is shown along the horizontal axis and bending strength in kg/mm² is shown along the vertical axis, derived from data relating to bending strength tests for the seventh set of preferred embodiments of the material of the present invention, said graph showing the relation between volume proportion of the reinforcing alumina short fiber material and bending strength of certain test pieces of the composite material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The present invention will now be described with reference to the various preferred embodiments thereof. It should be noted that all the tables referred to in this specification are to be found at the end of the specification and before the claims thereof: the present specification is arranged in such a manner in order to maximize ease of pagination.

THE FIRST SET OF PREFERRED EMBODIMENTS

[0028] In order to assess what might be the most suitable composition for an aluminum alloy to be utilized as matrix metal for a contemplated composite material of the type described in the preamble to this specification, the reinforcing material of which is to be alumina short fibers, the present inventors manufactured by using the high pressure casting method samples of various composite materials, utilizing as reinforcing material alumina fiber material of type "Saffil RF" (this is a trademark) made by ICI K.K., which were approximately 95% delta A1203 and remainder substantially Si02, and which had average fiber length 2 cm and average fiber diameter 3 microns, and utilizing as matrix metal Al-Cu-Mg type aluminum alloys of various compositions. Then the present inventors conducted evaluations of the bending strength of the various resulting composite material sample pieces.

[0029] First, a set of aluminum alloys designated as Al through A76 were.produced, having as base material aluminum and having various quantities of magnesium and copper mixed therewith, as shown in the appended Table 1; this was done by, in each case, introducing an appropriate quantity of substantially pure aluminum metal (purity at least 99%) and an appropriate quantity of substantially pure magnesium metal (purity at least 99%) into an alloy of approximately 50% aluminum and approximately 50% copper. And an appropriate number of alumina fiber material preforms were made by, in each case, subjecting a quantity of the above specified alumina fiber material to compression forming without using any binder. Each of these alumina fiber material preforms was, as schematically illustrated in perspective view in Fig. 1 wherein an exemplary such preform is designated by the reference numeral 2 and the alumina fibers therein are generally designated as 1, about 36 x 100 x 16 mm in dimensions, and the individual alumina fibers 1 in said preform 2 were oriented substantially randomly in two dimensions, i.e. in the x-y plane parallel to the 36 x 100 mm face, and were overlapped in a two dimensionally random manner in the axis perpendicular to this plane. And the fiber volume proportion in each of said preforms 2 was approximately 30%.

[0030] Next, each of these alumina fiber material preforms 2 was subjected to high pressure casting together with an appropriate quantity of one of the aluminum alloys Al through A76 described above, in the following manner. First, the preform 2 was inserted into a stainless steel case 2a, as shown in Fig. 2; this stainless steel case 2a was a rectangular parallelopiped and was open at both its ends. Then the preform 2 with the stainless steel case 2 were together heated up to a temperature of approximately 600°C, and then said preform 2 and its case 2a were placed within a mold cavity 4 of a casting mold 3, which itself had previously been preheated up to a temperature of approximately 250°C. Next, a quantity 5 of the appropriate one of the aluminum alloys A1 to A76 described above, molten and at a temperature of approximately 710°C, was relatively rapidly poured into said mold cavity 4, so as to surround the preform 2 therein, and then as shown in schematic view in Fig. 3 a pressure plunger 6, which itself had previously been preheated up to a temperature of approximately 200°C, which closely cooperated with the upper portion of said mold cavity 4 was inserted into said upper mold cavity portion, and was pressed downwards by a means not shown in the figure so as to pressurize said to a pressure of approximately 1000 kg/cm². Thereby, the molten aluminum alloy was caused to percolate into the interstices of the alumina material preform 2. This pressurized state was maintained until the quantity 5 of molten aluminum alloy had completely solidified, and then the pressure plunger 6 was removed and the solidified aluminum alloy mass with the preform 2 included therein was removed from the casting mold 3, and the peripheral portion of said solidified aluminum alloy mass was machined away, and then from the stainless steel case 2a there was further extracted a sample piece of composite material which had alumina fiber material as reinforcing material and the appropriate one of the aluminum alloys Al through A76 as matrix metal. The volume proportion of alumina fibers in each of the resulting composite material sample pieces was approximately 30%.

[0031] Next, the following post processing steps were performed on the composite material samples. Irrespective of the magnesium content of the aluminum alloy matrix metal: those of said composite material samples whose matrix metal had a copper content of less than approximately 2% were subjected to liquidizing processing at a temperature of approximately 530°C for approximately 8 hours, and then were subjected to artificial aging processing at a temperature of approximately 160°C for approximately 8 hours; those of said composite material samples whose matrix metal had a copper content of at least approximately 2% and not more than approximately 3.5% were subjected to liquidizing processing at a temperature of approximately 500°C for approximately 8 hours, and then were subjected to artificial aging processing at a temperature of approximately 160°C for approximately 8 hours; and those of said composite material samples whose matrix metal had a copper content of at least approximately 3.5% and not more than approximately 6.5% were subjected to liquidizing processing at a temperature of approximately 480°C for approximately 8 hours, and then were subjected to artificial aging processing at a temperature of approximately 160°C for approximately 8 hours.

[0032] From each of the composite material sample pieces manufactured as described above, to which heat treatment had been applied, there was cut a bending strength test piece of length approximately 50 mm, width approximately 10 mm, and thickness approximately 2 mm, with the 50 x 10 mm surface parallel to the plane of random two dimensional fiber orientation, and for each of these composite material bending strength test pieces a bending strength test was carried out, with a gap between supports of approximately 40 mm. In these bending strength tests, the bending strength of the composite material bending strength test piece was measured as the surface stress at breaking point M/Z (M is the bending moment at the breaking point, while Z is the cross section coefficient of the composite material bending strength test piece).

[0033] The results of these bending strength tests were as shown in the appended Table 2, and as summarized in the graphs of Fig. 4 and Fig. 5. The numerical values in Table 2 indicate the bending strengths (in -kg/mm^2-) of the composite material bending strength test pieces having as matrix metals aluminum alloys having percentage contents of copper and magnesium as shown along the upper edge and down the left edge of the table, respectively. The graphs of Fig. 4 are based upon the data in Table 2, and show the relation between copper content and the bending strength (in kg/mm²) of certain of the composite material test pieces, for percentage contents of magnesium fixed along the various lines thereof; and the graphs of Fig. 5 are also based upon the data in Table 2, and similarly but contrariwise show the relation between magnesium content and the bending strength (in kg/mm²) of certain of the composite material test pieces, for percentage contents of copper fixed along the various lines thereof. In Table 2, Fig. 4, and Fig. 5, the values for magnesium content and for copper content are shown with their second decimal places rounded by rounding .04 downwards to .0 and .05 upwards to .1.

[0034] From Table 2, Fig. 4, and Fig. 5, it will be understood that, substantially irrespective of the magnesium content of the aluminum alloy matrix metal of the bending strength composite material test pieces: when the copper content was either at the low extreme of approximately 1.5% or at the high extreme of approximately 6.5% the bending strength of the composite material had a relatively low value; when the copper content was in the range up to approximately 3% the bending strength of the composite material increased along with an increase in the copper content; when the copper content was in the range of approximately 3% to approximately 4.5% the bending strength of the composite material reached a maximum value; and, when the copper content was in the range of not less than approximately 4.5% the bending strength of the composite material had a tendency to reduce along with an increase in the copper content. Also, it will be understood that, substantially irrespective of the copper content of the aluminum alloy matrix metal of the bending strength composite material test pieces: when the magnesium content was either approximately 0% or approximately 4.5% the bending strength of the composite material had a relatively low value; when the magnesium content was approximately 3% the bending strength of the composite material had a substantially maximum value; when the magnesium content either increased or decreased from said optimal bending strength value of approximately 3% the bending strength of the composite material decreased gradually; and, when the magnesium content was approximately 4%, the bending strength of the composite material was substantially the same as when the magnesium content was approximately 2%.

[0035] It will be further seen from the values in Table 2 that, for such a composite material having a volume proportion of approximately 30% of alumina fiber material as reinforcing fiber material and using such an aluminum alloy as matrix metal, the bending strength values are generally very much higher than the typical bending strength of approximately 45 kg/mm² attained in the conventional art for a composite material using as matrix metal a conventionally so utilized aluminum alloy of JIS standard AC4C and using similar alumina short fiber material as reinforcing material; and in particular it will be appreciated that the bending strength of such a composite material whose matrix metal aluminum alloy has a copper content of from approximately 2% to approximately 6% and a magnesium content of from approximately 0.5% to approximately 4% is approximately between 1.4 and 1.7 times as great as that of such an abovementioned conventional composite material.

[0036] From the results of these bending strength tests it will be seen that, in order to increase the strength of a composite material having as reinforcing fiber material alumina fibers in a volume proportion of approximately 30% and having as matrix metal an Al-Cu-Mg type aluminum alloy, it is preferable that the copper content of said Al-Cu-Mg type aluminum alloy matrix metal should be in the range of from approximately 2% to approximately 6%, and particularly should be in the range of from approximately 2% to approximately 5.5%; and it is preferable that the magnesium content of said Al-Cu-Mg type aluminum alloy matrix metal should be in the range of from approximately 0.5% to approximately 4%, and particularly should be in the range of from approximately 2% to approximately 4%.

THE SECOND SET OF PREFERRED EMBODIMENTS

[0037] Next, the present inventors manufactured further samples of various composite materials, again utilizing as reinforcing material the same alumina fiber material, and utilizing as matrix metal various Al-Cu-Mg type aluminum alloys, but this time employing a fiber volume proportion of approximately 40%. Then the present inventors again conducted evaluations of the bending strength of the various resulting composite material sample pieces.

[0038] First, a set of aluminum alloys the same as those designated as Al through A76 in the case of the first set of preferred embodiments detailed above were produced in the same manner as before, and said alloys thus again had as base material aluminum and had various quantities of magnesium and copper mixed therewith. No particular table of proportions of magnesium and copper relating to these alloys of this second set of preferred embodiments like Table 1 and 3 for the alloys of the first set of preferred embodiments is appended, since none is required. And an appropriate number of alumina fiber material preforms were made as before by, in each case, subjecting a quantity of the previously utilized type of alumina fiber material to compression forming without using any binder, each of said alumina fiber material preforms 2 now having a fiber volume proportion of approximately 40%, by contrast to the first set of preferred embodiments described above; these preforms 2 had substantially the same dimensions as the preforms 2 of the first set of preferred embodiments. Next, substantially as before, each of these alumina fiber material preforms 2 was subjected to high pressure casting while included in a stainless steel case, together with an appropriate quantity of one of the aluminum alloys described above, utilizing operational parameters substantially as before, and, after machining away the peripheral portions of the resulting solidified aluminum alloy masses and extraction from the cases, sample pieces of composite material which had alumina fiber material as reinforcing material and the appropriate one of the above described aluminum alloys as matrix metal were obtained. And the volume proportion of alumina fibers in each of the resulting composite material sample pieces was thus now approximately 40%. Post processing steps were performed on the composite material samples, substantially as before, and from each of the composite material sample pieces manufactured as described above, to which heat treatment had been applied, there was cut a bending strength test piece of dimensions substantially as in the case of the first set of preferred embodiments, and for each of these composite material bending strength test pieces a bending strength test was carried out, again substantially as before. The results of these bending strength tests were as shown in the appended Table 3, and as summarized in the graphs of Fig. 6 and Fig. 7. Thus, Table 3, Fig. 6, and Fig. 7 correspond respectively to Table 2, Fig. 4, and Fig. 5 of the first set of preferred embodiments. As before, the numerical values in Table 3 indicate the bending strengths (in kg/mm²) of the composite material bending strength test pieces having as matrix metals aluminum alloys having percentage contents of copper and magnesium as shown along the upper edge and down the left edge of the table, respectively. The graphs of Fig. 6 are based upon the data in Table 3, and show the relation between copper content and the bending strength (in kg/mm2) of certain of the composite material test pieces, for percentage contents of magnesium fixed along the various lines thereof; and the graphs of Fig. 7 are also based upon the data in Table 3, and similarly but contrariwise show the relation between magnesium content and the bending strength (in kg/mm²) of certain of the composite material test pieces, for percentage contents of copper fixed along the various lines thereof. In Table 3, Fig. 6, and Fig. 7, as before, the values for magnesium content and for copper content are shown with their second decimal places rounded by rounding .04 downwards to .0 and .05 upwards to .1.

[0039] From Table 3, Fig. 6, and Fig. 7, it will be understood that, substantially irrespective of the magnesium content of the aluminum alloy matrix metal of the bending strength composite material test pieces: when the copper content was either at the low extreme of approximately 1.5% or at the high extreme of approximately 6.5% the bending strength of the composite material had a relatively low value; when the copper content was in the range of up to and including approximately 3% the bending strength of the composite material increased along with an increase in the copper content; when the copper content was approximately 3.5% the bending strength reached a substantially maximum value; and, when the copper content was in the range of not less than approximately 4% the bending strength of the composite material had a tendency to reduce along with an increase in the copper content. Also, it will be understood that, substantially irrespective of the copper content of the aluminum alloy matrix metal of the bending strength composite material test pieces: when the magnesium content was either approximately 0% or approximately 4.5% the bending strength of the composite material had a relatively low value; when the magnesium content was approximately 3% the bending strength of the composite material had a substantially maximum value; when the magnesium content either increased or decreased from approximately 3%, the bending strength of the composite material decreased gradually; and, when the magnesium content was approximately 4%, the bending strength of the composite material was substantially the same as when the magnesium content was approximately 1.5%.

[0040] It will be further seen from the values in Table 3 that, for such a composite material having a volume proportion of approximately 40% of alumina fiber material as reinforcing fiber material and using such an aluminum alloy as matrix metal, the bending strength values are generally very much higher than the typical bending strength of approximately 46 kg/mm2 attained in the conventional art for a composite material using as matrix metal a conventionally so utilized aluminum alloy of JIS standard AC4C and using similar alumina short fiber material as reinforcing material; and in particular it will be appreciated that the bending strength of such a composite material whose matrix metal aluminum alloy has a copper content of from approximately 2% to approximately 6% and a magnesium content of from approximately 0.5% to approximately 4% is approximately between 1.5 and 1.8 times as great as that of such an abovementioned conventional composite material.

[0041] From the results of these bending strength tests it will be seen that, also in this case when the volume proportion of the reinforcing alumina fibers is approximately 40% as in the previous cases when said volume proportion was approximately 30%, in order to increase the strength of such a composite material having such alumina fiber reinforcing fiber material and having as matrix metal an Al-Cu-Mg type aluminum alloy, it is again preferable that the copper content of said Al-Cu-Mg type aluminum alloy matrix metal should be in the range of from approximately 2% to approximately 6%, and particularly should be in the range of from approximately 2% to approximately 5.5%; and it is preferable that the magnesium content of said Al-Cu-Mg type aluminum alloy matrix metal should be in the range of from approximately 0.5% to approximately 4%, and particularly should be in the range of from approximately 2% to approximately 4%.

[0042] Further, from the results of the bending tests of the first and second sets of preferred embodiments, it was inferred that in the case that the volume proportion of alumina short fiber material is in the range of from 30% to 40% it is preferable for the copper content and the magnesium content to be within the abovementioned ranges.

THE THIRE SET OF PREFERRED EMBODIMENTS

[0043] Next, the present inventors manufactured further samples of various composite materials, again utilizing as reinforcing material the same alumina fiber material, and utilizing as matrix metal various other Al-Cu-Mg type aluminum alloys,.but this time employing a fiber volume proportion of only approximately 10%. Then the present inventors again conducted evaluations of the bending strength of the various resulting composite material sample pieces.

[0044] First, a set of aluminum alloys designated as B1 through B30 were produced in the same manner as before, again having as base material aluminum and having various quantities of magnesium and copper mixed therewith, as shown in the appended Table 4. And an appropriate number of alumina fiber material preforms were as before made by, in each case, subjecting a quantity of the previously utilized type of alumina fiber material to compression forming without using any binder, each of said alumina fiber material preforms 2 now having a fiber volume proportion of approximately 10%, by contrast to the first set of preferred embodiments described above. These preforms 2 had substantially the same dimensions as the preforms 2 of the first and second sets of preferred embodiments.

[0045] Next, substantially as before, each of these alumina fiber material preforms 2 was subjected to high pressure casting in a stainless steel case together with an appropriate quantity of one of the aluminum alloys B1 through B30 described above, utilizing operational parameters substantially as before. The solidified aluminum alloy mass with the preform 2 included therein was then removed from the casting mold, and the peripheral portion of said solidified aluminum alloy mass was machined away, leaving, after extraction from the stainless steel case, a sample piece of composite material which had alumina fiber material as reinfbrcing material and the appropriate one of the aluminum alloys Bl through B30 as matrix metal. The volume proportion of alumina fibers in each of the resulting composite material sample pieces was thus now approximately 10%. And post processing steps were performed on the composite material samples, substantially as before. From each of the composite material sample pieces manufactured as described above, to which heat treatment had been applied, there was cut a bending strength test piece of dimensions substantially as in the case of the first and second sets of preferred embodiments, and for each of these composite material bending strength test pieces a bending strength test was carried out, again substantially as before.

[0046] The results of these bending strength tests were as shown in the appended Table 5, and as summarized in the graphs of Fig. 8 and Fig. 9. The numerical values in Table 5 indicate the bending strengths (in kg/mm²) of the composite material bending strength test pieces having as matrix metals aluminum alloys having percentage contents of copper and magnesium as shown along the upper edge and down the left edge of the table, respectively. The graphs of Fig. 8 are based upon the data in Table 5, and show the relation between copper content and the bending strength (in kg/mm²) of certain of the composite material test pieces, for percentage contents of magnesium fixed along the various lines thereof; and the graphs of Fig. 9 are also based upon the data in Table 5, and similarly but contrariwise show the relation between magnesium content and the bending strength (in kg/mm2) of certain of the composite material test pieces, for percentage contents of copper fixed along the various lines thereof. In Table 5, Fig. 8, and Fig. 9, as before, the values for magnesium content and for copper content are shown with their second decimal places rounded by rounding .04 downwards to .0 and .05 upwards to .1.

[0047] From Table 5, Fig. 8, and Fig. 9, it will be understood that, substantially irrespective of the magnesium content of the aluminum alloy matrix metal of the bending strength composite material test pieces: when the copper content was either at the low extreme of approximately 1.5% or at the high extreme of approximately 6.5% the bending strength of the composite material had a relatively low value; when the copper content was in the range of up to and including approximately 3% the bending strength of the composite material increased along with an increase in the copper content; when the copper content was in the range of approximately 4% to approximately 5% the bending strength reached a substantially maximum value; when the copper content was in the range of not less than approximately 5% the bending strength of the composite material had a tendency to reduce along with an increase in the copper contentd; and the bending strength, in the case that the copper content was approximately 2%, was less than the bending strength when said copper content was approximately 6%. Also, it will be understood that, substantially irrespective of the copper content of the aluminum alloy matrix metal of the bending strength composite material test pieces: when the magnesium content was either below approximately 2% or above approximately 4% the bending strength of the composite material had a relatively low value; when the magnesium content was from approximately 2% to approximately 3% the bending strength of the composite material had a substantially maximum value; when the magnesium content either increased or decreased from approximately 2% to approximately 3%, the bending strength of the composite material decreased gradually.

[0048] It will be further seen from the values in Table 5 that, for such a composite material having a volume proportion of approximately 10% of alumina fiber material as reinforcing fiber material and using such an aluminum alloy as matrix metal, the bending strength values are generally very much higher than the typical bending strength of approximately 40 kg/mm2 attained in the conventional art for a composite material using as matrix metal a conventionally so utilized aluminum alloy of JIS standard AC4C and using similar alumina short fiber material as reinforcing material; and in particular it will be appreciated that the bending strength of such a composite material whose matrix metal aluminum alloy has a copper content of from approximately 2% to approximately 6% and a magnesium content of from approximately 2% to approximately 4% is approximately between 1.4 and 1.6 times as great as that of such an abovementioned conventional composite material.

[0049] From the results of these bending strength tests it will be seen that, also in this case when the volume proportion of the reinforcing alumina fibers is approximately 10% as in the previous cases when said volume proportion was approximately 30% and said volume proportion was approximately 40%, in order to increase the strength of such a composite material having such alumina fiber reinforcing fiber material and having as matrix metal an Al-Cu-Mg type aluminum alloy, it is again preferable that the copper content of said Al-Cu-Mg type aluminum alloy matrix metal should be in the range of from approximately 2% to approximately 6%, and particularly should be in the range of from approximately 3% to approximately 6%; and it is preferable that the magnesium content of said Al-Cu-Mg type aluminum alloy matrix metal should be in the range of from approximately 2% to approximately 4%.

THE FOURTH SET OF PREFERRED EMBODIMENTS

[0050] For the fourth set of preferred embodiments of the present invention, the present inventors manufactured by using the high pressure casting method samples of various composite materials, utilizing as reinforcing material the same alumina fiber material as utilized before. Then the present inventors conducted evaluations of the bending strength of the various resulting composite material sample pieces,

[0051] In detail, first, a set of aluminum alloys designated as B1 through B30 were produced in the same manner as in the third set of preferred embodiments described above, and thus the previously described Table 4 is applicable to this fourth set of preferred embodiments also. And an appropriate number of alumina fiber material preforms were made in the same manner as before, but each of the resulting alumina fiber material preforms 2 now having a alumina short fiber volume proportion of approximately 5%, by contrast to the first through the third sets of preferred embodiments described above. These preforms 2 had substantially the same dimensions of about 38 x 100 x 16 mm as the preforms 2 of the first through the third sets of preferred embodiments described above, and as before in this case the alumina short fibers incorporated therein were oriented substantially randomly in planes parallel to their 38 mm x 100 mm faces, and had randomly overlapping orientation in the thickness direction orthogonal to these planes.

[0052] Next, substantially as before, each of these alumina fiber material preforms was subjected to high pressure casting together with an appropriate quantity of one of the aluminum alloys B1 through B30 described above, utilizing operational parameters substantially as before. The solidified aluminum alloy mass with the preform included therein was then removed from the casting mold, and the peripheral portion of said solidified aluminum alloy mass was machined away, leaving after extraction from the case a sample piece of composite material which had alumina fiber material as reinforcing material and the appropriate one of the aluminum alloys B1 through B30 as matrix metal. The volume proportion of alumina fibers in each of the resulting composite material sample pieces was thus now approximately 5%. And post processing steps of liquidizing processing and artificial aging processing were performed on the composite material samples, substantially as before. From each of the composite material sample pieces manufactured as described above, to which heat treatment had been applied, there was cut a bending strength test piece of length approximately 50 mm, width approximately 10 mm, and thickness approximately 2 mm, substantially as before, with its 50 mm x 10 mm faces parallel to the planes of random two dimensional fiber orientation of the alumina short fiber material included therein, and for each of these composite material bending strength test pieces a bending strength test was carried out, again substantially as before.

[0053] The results of these bending strength tests were as shown in the appended Table 6, and as summarized in the graphs of Fig. 10 and Fig. 11. The numerical values in Table 6 indicate the bending strengths (in Kg/mm²) of the composite material bending strength test pieces having as matrix metals aluminum alloys having percentage contents of copper and magnesium as shown along the upper edge and down the left edge of the table, respectively. The graphs of Fig. 10 are based upon the data in Table 6, and show the relation between copper content and the bending strength (in kg/mm²) of certain of the composite material test pieces, for percentage contents of magnesium fixed along the various lines thereof; and the graphs of Fig. 11 are also based upon the data in Table 6, and similarly but contrariwise show the relation between magnesium content and the bending strength (in kg/mm2) of certain of the composite material test pieces, for percentage contents of copper fixed along the various lines thereof. In Table 6, Fig. 10, and Fig. 11, as before, the values for magnesium content and for copper content are shown with their second decimal places rounded by rounding .04 downwards to .0 and .05 upwards to .1.

[0054] From Table 6, Fig. 10, and Fig. 11, it will be understood that, substantially irrespective of the magnesium content of the aluminum alloy matrix metal of the bending strength composite material test pieces: when the copper content was either at the low extreme of approximately 1.5% or at the high extreme of approximately 6.5% the bending strength of the composite material had a relatively low value; when the copper content was in the range of up to and including approximately 3% the bending strength of the composite material increased along with an increase in the copper content; when the copper content was approximately 4% to approximately 5% the bending strength reached a substantially maximum value; when the copper content was greater than approximately 5% the bending strength of the composite material had a tendency to reduce along with an increase in the copper content; and, further, when the copper content was approximately 2% the bending strength was lower than the bending strength when the copper content was approximately 6%. Also, it will be understood that, substantially irrespective of the copper content of the aluminum alloy matrix metal of the bending strength composite material test pieces: when the magnesium content was either below approximately 2% or above approximately 4% the bending strength of the composite material had a relatively low value; when the magnesium content was in the range of from approximately 2% to approximately 3% the bending strength of the composite material had a substantially maximum value; when the magnesium content either increased or decreased from approximately 3%, the bending strength of the composite material decreased gradually.

[0055] It will be further seen from the values in Table 6 that, for such a composite material having a volume proportion of approximately 5% of alumina fiber material as reinforcing fiber material and using such an aluminum alloy as matrix metal, the bending strength values are generally very much higher than the typical bending strength of approximately 38 kg/mm^2-attained in the conventional art for a composite material using as matrix metal a conventionally so utilized aluminum alloy of JIS standard AC4C and using similar alumina short fiber material as reinforcing material; and in particular it will be appreciated that the bending strength of such a composite material whose matrix metal aluminum alloy has a copper content of from approximately 2% to approximately 6% and a magnesium content of from approximately 2% to approximately 4% is approximately between 1.4 and 1.6 times as great as that of such an abovementioned conventional composite material.

[0056] From the results of-these bending strength tests it will be seen that, also in this case when the volume proportion of this type of reinforcing alumina fibers is approximately 5% as in the previous cases relating to the first through the third volume proportions of reinforcing alumina fibers, in order to increase the strength of such a composite material having such alumina fiber reinforcing fiber material and having as matrix metal an Al-Cu-Mg type aluminum alloy, it is again preferable that the copper content of said Al-Cu-Mg type aluminum alloy matrix metal should be in the range of from approximately 2% to approximately 6%, and particularly should be in the range of from approximately 3% to approximately 6%; and it is preferable that the magnesium content of said Al-C_U-Mg type aluminum alloy matrix metal should be in the range of from approximately 2% to approximately 4%.

THE FIFTH SET OF PREFERRED EMBODIMENTS

[0057] Next, the present inventors manufactured further samples of various composite materials, now utilizing as reinforcing material a different type of alumina fiber material from the first through the fourth sets of preferred embodiments described above, and utilizing as matrix metal various Al-Cu-Mg type aluminum alloys, but this time employing a fiber volume proportion of approximately 15%. Then the present inventors again conducted evaluations of the bending strength of the various resulting composite material sample pieces.

[0058] First, a set of aluminum alloys the same as those designated as Bl through B30 in the case of the second and the fourth sets of preferred embodiments were produced in the same manner as before, and said alloys thus again had as base material aluminum and had various quantities of magnesium and copper mixed therewith. No particular table of proportions of magnesium and copper relating to these alloys of this fifth set of preferred embodiments is appended, since none is required. And an appropriate number of alumina fiber material preforms were made by, in each case, subjecting a quantity of alumina fiber material of type "Arusen" manufactured by Denki Kagaku Kogyo KK, which were approximately 80% alpha A1203 and remainder substantially Si02, and had average fiber length about 2 cm and average fiber diameter about 2 microns, to compression forming as in the case of the previous sets of embodiments, each of said alumina fiber material preforms 2 now having a fiber volume proportion of approximately 15%, by contrast to the other sets of preferred embodiments described above; these preforms 2 had substantially the same dimensions as the preforms 2 of the previously described sets of preferred embodiments, and the same type of random two dimensional fiber orientation. Next, substantially as before, each of these alumina fiber material'preforms 2 was subjected to high pressure casting together with an appropriate quantity of one of the aluminum alloys described above, utilizing operational parameters substantially as before, and, after machining away the peripheral portions of the resulting solidified aluminum alloy masses and removing the stainless steel cases, sample pieces of composite material which had alumina fiber material as reinforcing material and the appropriate one of the above described aluminum alloys as matrix metal were obtained.

[0059] And the volume proportion of alumina fibers in each of the resulting composite material sample pieces was thus now approximately 15%. Post processing steps were performed on the composite material samples, substantially as before, and from each of the composite material sample pieces manufactured as described above, to which heat treatment had again been applied, there was cut a bending strength test piece of dimensions substantially as in the case of the previous sets of preferred embodiments and with fiber orientation substantially as described above, and for each of these composite material bending strength test pieces a bending strength test was carried out, again substantially as before. The results of these bending strength tests were as shown in the appended Table 7, and as summarized in the graphs of Fig. 12 and Fig. 13. Thus, Table 7, Fig. 12, and Fig. 13 correspond respectively to Table 6, Fig. 10, and Fig. 11 of the fourth set of preferred embodiments described above. As before, the numerical values in Table 7 indicate the bending strengths (in kg/mm2-) of the composite material bending strength test pieces having as matrix metals aluminum alloys having percentage contents of copper and magnesium as shown along the upper edge and down the left edge of the table, respectively. The graphs of Fig. 12 are based upon the data in Table 7, and show the relation between copper content and the bending strength (in kg/mm2) of certain of the composite material test pieces, for percentage contents of magnesium fixed along the various lines thereof; and the graphs of Fig. 13 are also based upon the data in Table 7, and similarly but contrariwise show the relation between magnesium content and the bending strength (in kg/mm²) of certain of the composite material test pieces, for percentage contents of copper fixed along the various lines thereof,. In Table 7, Fig. 12, and Fig. 13, as before, the values for magnesium content and for copper content are shown with their second decimal places rounded by rounding .04 downwards to .0 and .05 upwards to .1.

[0060] From Table 7, Fig. 12, and Fig. 13, it will be understood that, substantially irrespective of the magnesium content of the aluminum alloy matrix metal of the bending strength composite material test pieces: when the copper content was either at the low extreme of approximately 1.5% or at the high extreme of approximately 6.5% the bending strength of the composite material had a relatively low value; when the copper content was in the range of up to and including approximately 4% the bending strength of the composite material increased along with an increase in the copper content; when the copper content was approximately 5% the bending strength reached a substantially maximum value; when the copper content was in the range of not less than approximately 5% the bending strength of the composite material had a tendency to reduce along with an increase in the copper content; and, when the copper content was approximately 2%, the bending strength of the composite material was substantially less than when the copper content was approximately G%. Also, it will be understood that, substantially irrespective of the copper content of the aluminum alloy matrix metal of the bending strength composite material test pieces: when the magnesium content was either below approximately 2% or above approximately 4% the bending strength of the composite material had a relatively low value; when the magnesium content was approximately 3% the bending strength of the composite material had a substantially maximum value; when the magnesium content either increased or decreased from approximately 3%, the bending strength of the composite material had a tendency to decrease gradually.

[0061] It will be further seen from the values in Table 7 that, for such a composite material having a volume proportion of approximately 15% of alumina fiber material as reinforcing fiber material and using such an aluminum alloy as matrix metal, the bending strength values are generally very much higher than the typical bending strength of approximately 41 kg/mm2 attained in the conventional art for a composite material using as matrix metal a conventionally so utilized aluminum alloy of JIS standard AC4C and using similar alumina short fiber material as reinforcing material; and in particular it will be appreciated that the bending strength of such a composite material whose matrix metal aluminum alloy has a copper content of from approximately 2% to approximately 6% and a magnesium content of from approximately 2% to approximately 4% is approximately between 1.4 and 1.6 times as great as that of such an abovementioned conventional composite material.

[0062] From the results of these bending strength tests it will be seen that, also in this case when the volume proportion of the reinforcing alumina fibers is approximately 15% as in the previous cases, in order to increase the strength of such a composite material having . such alumina fiber reinforcing fiber material and having as matrix metal an Al-Cu-Mg type aluminum alloy, it is again preferable that the copper content of said Al-Cu-Mg type aluminum alloy matrix metal should be in the range of from approximately 2% to approximately 6%, and particularly should be in the range of from approximately 3% to approximately 6%; and it is preferable that the magnesium content of said Al-Cu-Mg type aluminum alloy matrix metal should be in the range of from approximately 2% to approximately 4%.

THE SIXTH SET OF PREFERRED EMBODIMENTS

[0063] Next, the present inventors manufactured further samples of various composite materials, again utilizing as reinforcing material the same alumina fiber material as in the fifth set of preferred embodiments described above, and utilizing as matrix metal various Al-Cu-Mg type aluminum alloys, but this time employing a fiber volume proportion of approximately 20%. Then the present inventors again conducted evaluations of the bending strength of the various resulting composite material sample pieces.

[0064] First, a set of aluminum alloys the same as those designated as Bl through B30 in the case of the previously described sets of preferred embodiments were produced in the same manner as before, and said alloys B1 through B30 thus again had as base material aluminum and had various quantities of magnesium and copper mixed therewith. No particular table of proportions of magnesium and copper relating to these alloys is appended, since again none is required. And an appropriate number of alumina fiber material preforms were made as before by, in each case, subjecting a quantity of the same type of alumina fiber material as utilized in the fifth set of preferred embodiments to compression forming as described with regard to said fifth set of preferred embodiments, each of said alumina fiber material preforms 2 now having a fiber volume proportion of approximately 20% by contrast to said fifth set of preferred embodiments; these preforms 2 had substantially the same dimensions as the preforms 2 of the fifth set of preferred embodiments, and the same type of fiber orientation. Next, substantially as before, each of these alumina fiber material preforms 2 was subjected to high pressure casting in a stainless steel case together with an appropriate quantity of one of the aluminum alloys described above, utilizing operational parameters substantially as before, and, after machining away the peripheral portions of the resulting solidified aluminum alloy masses, and removing the cases, sample pieces of composite material which had alumina fiber fiber material as reinforcing material and the appropriate one of the above described aluminum alloys as matrix metal were obtained. And the volume proportion of alumina fibers in each of the resulting composite material sample pieces was thus now approximately 20%. Post processing steps were performed on the composite material samples, substantially as before, and from each of the composite material sample pieces manufactured as described above, to which heat treatment had again been applied, there was cut a bending strength test piece of dimensions substantially as in the case of the previously described sets of preferred embodiments and with fiber orientation substantially as described above, and for each of these composite material bending strength test pieces a bending strength test was carried out, again substantially as before. The results of these bending strength tests were as shown in the appended Table 8, and as summarized in the graphs of Fig. 14 and Fig. 15. Thus, Table 8, Fig. 14, and Fig. 15 correspond respectively to Table 7, Fig. 12, and Fig. 13 of the fifth set of preferred embodiments described above. As before, the numerical values in Table 8 indicate the bending strengths (in kg/mm²) of the composite material bending strength test pieces having as matrix metals aluminum alloys having percentage contents of copper and magnesium as shown along the upper edge and down the left edge of the table, respectively. The graphs of Fig. 14 are based upon the data in Table 8, and show the relation between-copper content and the bending strength (in kg/mm2) of certain of the composite material test pieces, for percentage contents of magnesium fixed along the various lines thereof; and the graphs of Fig. 15 are also based upon the data in Table 8, and similarly but contrariwise show the relation between magnesium content and the bending strength (in kg/mm²) of certain of the composite material test pieces, for percentage contents of copper fixed along the various lines thereof. In Table 8, Fig. 14, and Fig. 15, as before, the values for magnesium content and for copper content are shown with their second decimal places rounded by rounding .04 downwards to .0 and .05 upwards to .1.

[0065] From Table 8, Fig. 14, and Fig. 15, it will yet again be understood that, substantially irrespective of the magnesium content of the aluminum alloy matrix metal of the bending strength composite material test pieces: when the copper content was either at the low extreme of approximately 1.5% or at the high extreme of approximately 6.5% the bending strength of the composite material had a relatively low value; when the copper content was in the range of up to and including approximately 4% the bending strength of the composite material increased along with an increase in the copper content; when the copper content was in the range of from approximately 4% to approximately 5% the bending strength reached a substantially maximum value; when the copper content was in the range of not less than approximately 5% the bending strength of the composite matemial had a tendency to reduce along with an increase in the copper content; and, when the copper content was approximately 2%, the bending strength of the composite material was substantially less than when the magnesium content was approximately 6%. Also, it will be yet again understood that, substantially irrespective of the copper content of the aluminum alloy matrix metal of the bending strength composite material test pieces: when the magnesium content was either below approximately 2% or above approximately 4% the bending strength of the composite material had a relatively low value; when the magnesium content was approximately 3% the bending strength of-the composite material had a substantially maximum value; and, when the magnesium content either increased or decreased from approximately 3%, the bending strength of the composite material had a tendency to decrease gradually.

[0066] It will be further seen from the values in Table 8 that, for such a composite material having a volume proportion of approximately 20% of such alumina fiber material as reinforcing fiber material and using such an aluminum alloy as matrix metal, the bending strength values are generally very much higher than the typical bending strength of approximately 43 kg/mm2 attained in the conventional art for a composite material using as matrix metal a conventionally so utilized aluminum alloy of JIS standard AC4C and using similar alumina short fiber material as reinforcing material; and in particular it will be appreciated that the bending strength of such a composite material whose matrix metal aluminum alloy has a copper content of from approximately 2% to approximately 6% and a magnesium content of from approximately 2% to approximately 4% is approximately between 1.4 and 1.7 times as great as that of such an abovementioned conventional composite material.

[0067] From the results of these bending strength tests it will be seen that, also in this case when the volume proportion of the reinforcing alumina fibers is approximately 20% as in the previous cases, in order to increase the strength of such a composite material having such alumina fiber reinforcing fiber material and having as matrix metal an Al-Cu-Mg type aluminum alloy, it is again preferable that the copper content of said Al-Cu-Mg type aluminum alloy matrix metal should be in the range of from approximately 2% to approximately 6%, and particularly should be in the range of from approximately 3% co approximately 6%; and it is preferable that the mag esium content of said Al-Cu-Mg type aluminum alloy mat:ix metal should be in the range of from approximately 2% co approximately 4%.

[0068] Thus, from the results of the bending strength tests detailed above with regard to the third through the sixth sets of preferred embodiments, it was,inferred that, in the case of a composite material having as reinforcing fiber material alumina fibers in a fiber volume proportion of from 5% to 20%, it is preferable that the copper content of the aluminum alloy matrix metal should be from approximately 2% to approximately 6%; and that it is even more preferable that said copper content of the aluminum alloy matrix metal should be from approximately 3% to approximately 6%.

OTHER-EMBODIMENTS

[0069] Although no particular details thereof are given in the interests of brevity of description, in fact other sets of preferred embodiments similar to the first through the sixth sets of preferred embodiments described above were produced, in similar manners to those described above, but differing in that the alumina short fibers which constituted the reinforcing material were in these cases alumina continuous fibers "FP fiber" made by Dupont, average fiber diameter 20 microns, cut to a length of approximately 1 cm; and bending strength tests of the same types as conducted in the first through the sixth sets of preferred embodiments described above were carried out on bending test sampler which as before had their 50 mm x 10 mm faces extending parallel to the planes of random two dimensional fiber orientation of the alumina short fiber material included in said test samples. The results of these bending strength tests were similar to those described above for said first through sixth sets of preferred embodiments, and the conclusions drawn therefrom were accordingly similar.

THE SEVENTH SET OF PREFERRED EMBODIMENTS

[0070] Since from the above described first through the sixth sets of preferred embodiments the fact has been amply established and demonstrated that it is preferable for the copper content of the Al-Cu-Mg type aluminum alloy matrix metal to be in the range of from approximately 2% to approximately 6%, and that it is preferable that the magnesium content of said Al-Cu-Mg type aluminum alloy matrix metal to be in the range of from approximately 2% to approximately 4%, it is now germane to provide a set of tests to establish what fiber volume proportion of the reinforcing alumina short fibers is most appropriate. This was done, in the seventh set of preferred embodiments now described, by varying said fiber volume proportion of the reinforcing alumina fiber material while using an Al-Cu-Mg type aluminum alloy matrix metal which had the proportions of copper and magnesium which had as described above been established as being quite good, i.e. which had copper content of approximately 4% and magnesium content of approximately 3% and remainder substantially aluminum. In other words, an appropriate number of alumina fiber material preforms were as before made by, in each case, subjecting a quantity of the type of alumina fiber material utilized in the case of the first set of preferred embodiments described above to compression forming without using any binder, the various ones of said alumina fiber material preforms having fiber volume proportions of approximately 0%, 5%, 10%, 15%, 30%, 40%, and 50%. These preforms had substantially the same dimensions and the same type of three dimensional random fiber orientation as the preforms of the first set of preferred embodiments. And, substantially as before, each of these alumina fiber material preforms was subjected to high pressure casting together with an appropriate quantity of one of the aluminum alloy matrix metal described above, utilizing operational parameters substantially as before. The solidified aluminum alloy mass with the preform included therein was then removed from the casting mold, and as before the peripheral portion of said solidified aluminum alloy mass was machined away, leaving after case removal a sample piece of composite material which had alumina fiber material as reinforcing material in the appropriate fiber volume proportion and the described aluminum alloy as matrix metal. And post processing steps were performed on the composite material samples, similarly to what was done before: the composite material samples were subjected to liquidizing processing at a temperature of approximately 500°C for approximately 8 hours, and then were subjected to artificial aging processing at a temperature of approximately 160°C for approximately 8 hours. From each of the composite material sample pieces manufactured as described above, to which heat treatment had been applied, there were then cut two bending strength test pieces, each of dimensions substantially as in the case of the first set of preferred embodiments, and for each of these composite material bending strength test pieces a bending strength t_E.;t was carried out, again substantially as before. The results of these bending strength tests were as shown in the graph of Fig. 16, which shows the relation between the volume proportion of the alumina short reinforcing filpers and the bending strength (in kg/mm²) of the corposite material test pieces.

[0071] From Fig. 16, it will be understood that: when the volume proportion of the alumina short reinforcing fibers was in the range of up to and including approximately 5% the bending strength of the composite material hardly increased along with an increase in the fiber volume proportion, and its value was close to the bending strength of the aluminum alloy matrix metal by itself with no reinforcing fiber material admixtured therewith; when the volume proportion of the alumina short reinforcing fibers was in the range of 5% to 40% the bending strength of the composite material increased greatly, and substantially linearly along with increasing fiber volume proportion; and, when the volume proportion of the alumina short reinforcing fibers increased above 40%, the bending strength of the composite material hardly increased along with any further increase in the fiber volume proportion, but remained substantially constant.

OTHER EMBODIMENTS

[0072] Although no particular details thereof are given in the interests of brevity of description, in fact two other sets of preferred embodiments similar to the seventh set of preferred embodiments described above were produced, in a similar manner to that described above, but differing in that in one of them the Al-Cu-Mg type aluminum alloy matrix metal utilized therein had copper content of approximately 2% and magnesium content of approximately 4% and remainder substantially aluminum, and in the other one of them said Al-Cu-Mg type aluminum alloy matrix metal utilized therein had copper content of approximately 6% and magnesium content of approximately 2% and remainder substantially aluminum; and bending strength tests of the same types as conducted in the seventh set of preferred embodiments described above were carried out on similar bending test samples. The results of these bending strength tests were similar to those described above for said seventh set of preferred embodiments and shown in Fig. 16, and the conclusions drawn therefrom were accordingly similar.

[0073] Further, although again no particular details thereof are given in the interests of brevity of description, another set of preferred embodiments similar to the seventh set of preferred embodiments described above was produced, in a similar manner to that described above, with the Al-Cu-Mg type aluminum alloy matrix metal utilized therein similarly having copper content of approximately 4% and magnesium content of approximately 3% and remainder substantially aluminum, but now utilizing a type of alumina short fiber reinforcing material the same as that used in the fifth set of preferred embodiments described above; and bending strength tests of the same type as conducted in the seventh set of preferred embodiments described above were carried out on similar bending test samples. The results of these bending strength tests were analogous to those described above for said seventh set of preferred embodiments and shown in Fig. 16, and exhibited the same trends; the conclusions drawn therefrom were accordingly again similar.

[0074] From these results described above, it is seen that in a composite material having alumina short fiber reinforcing material and having as matrix metal an Al-Cu-Mg type aluminum alloy, said Al-Cu-Mg type aluminum alloy matrix metal having a copper content in the range of from approximately 2% to approximately 6%, a magnesium content in the range of from approximately 2% to approximately 4%, and remainder substantially aluminum, it is preferable that the fiber volume proportion of the alumina short fiber reinforcing material should be in the range of from approximately 5% to approximately 50%, and more preferably should be in the range of from approximately 5% to approximately 40%.

[0075] Although the present invention has been shown and described in terms of certain sets of preferred embodiments thereof, and with reference to the appended drawings, it should not be considered as being particularly limited thereby. The details of any particular embodiment, or of the drawings, could be varied without, in many cases, departing from the ambit of the present invention. Accordingly, the scope of the present invention is to be considered as being delimited, not by any particular perhaps entirely fortuitous details of the disclosed preferred embodiments, or of the drawings, but solely by the legitimate and properly interpreted scope of the accompanying claims, which follow after the Tables.

Claims

1. A composite material, comprising alumina short fibers embedded in a matrix of metal, the fiber volume proportion of said alumina short fibers being between approximately 5% and approximately 50%, and said metal being an alloy consisting essentially of between approximately 2% to approximately 6% of copper, between approximately 0.5% to approximately 4% of magnesium, and remainder substantially aluminum.

2. A composite material according to claim 1, wherein the fiber volume proportion of said crystalline alumina short fibers is between approximately 5% and approximately 40%.

3. A composite material according to claim 1 or claim 2, wherein the magnesium content of said aluminum alloy matrix metal is between approximately 2% and approximately 4%.

4. A composite material according to claim 3, wherein the fiber volume proportion of said alumina short fibers is between approximately 5% and approximately 20%, and the copper content of said aluminum alloy matrix metal is between approximately 3% and approximately 6%.

5. A composite material according to claim 3, wherein the fiber volume proportion of said alumina short fibers is between approximately 30% and approximately 40%, and the copper content of said aluminum alloy matrix metal is between approximately 2% and approximately 5%.

6. A composite material according to claim 1, wherein said alumina short fibers are essentially composed of delta alumina.

7. A composite material according to claim 1, wherein said alumina short fibers are essentially composed of alpha alumina.

Drawing