Field of the invention
[0001] The present invention relates to new multicomponent aluminium alloys, with certain
proportions of zinc, copper and magnesium, as well as with a silicon content; these
alloys have fine microstructures, which allow their processability by means of different
manufacturing techniques, including technologies where the rapid solidification of
the process presents hot cracking problems and processes where porosity is generated.
The fine microstructure of these new alloys is made up of a saturated solid solution
as a matrix and an interdendritic region formed by eutectic compounds.
State of the art
[0002] Aluminium is a light metal with a density of 2.70 g/cm
3, and its alloys have lower mechanical properties than those of steel, although they
have an excellent strength-to-weight ratio. Therefore, they are used when the weight
factor is relevant, such as, for example, in aeronautical and automotive applications.
[0003] Aluminium alloys can be subdivided into two large groups, for forging and casting,
depending on the manufacturing process.
[0004] Alloys for forging, that is, alloys used for the manufacture of sheets, films, extruded
profiles, rods and wires, are classified according to the alloying elements they contain,
based on a four-digit numerical code. They can be further subdivided into two groups,
heat-treatable alloys and non-heat-treatable alloys; these latter alloys cannot be
precipitation hardened and can only be cold worked to increase their strength.
[0005] Aluminium alloys for casting are characterised by their good castability, fluidity
and mould feeding qualities, as well as by the optimisation of their properties of
strength and toughness or corrosion resistance. To improve strength properties, the
parts are cooled in moulds that allow high cooling rates. Nevertheless, these alloys
are relatively limited in terms of their mechanical properties.
[0006] Some additive manufacturing techniques that are becoming increasingly relevant, such
as L-PBF (laser powder bed fusion), L-DED (laser directed energy deposition) or WAAM
(wire arc additive manufacturing), together with other more conventional processes,
such as welding processes or pressure die casting (HPDC or high pressure die casting),
involve process conditions with high cooling rates, generally greater than 50 °C/s.
These cooling rates make it impossible to process some high-strength aluminium alloys.
Commercial series of high strength or precipitation hardenable aluminium, for example,
those belonging to the 2xx.x (Al-Cu) or 7xx.x (Al-Zn) series, were specifically developed
for extrusion, rolling and forging processes, manufacturing processes with their corresponding
intrinsic process characteristics, starting from ingots and slabs manufactured with
solidification rates of the order of 3 °C/s or less. The processing of these alloys
with higher cooling rates generates problems such as hot cracking, porosity, etc.
[0007] Therefore, there remains a need in the state of the art to achieve high-strength
alloys that can be processed by techniques that involve cooling rates during solidification
greater than 50 °C/s, but with low susceptibility to hot cracking and porosity.
[0008] The present invention provides high-strength alloys which can be processed by techniques
that involve cooling rates during solidification greater than 50 °C/s due to their
low susceptibility to hot cracking and porosity.
[0009] Most high-strength commercial aluminium alloys used in the automotive or aerospace
industries owe their high mechanical properties to precipitation hardening. Precipitation
hardening consists of the formation of small and dispersed precipitates of a second
phase within the aluminium matrix, usually by heat treatment, improving the hardness
of the alloy. These alloys were designed for conventional processes, such as forging,
which, although they are susceptible to precipitation hardening, and therefore have
better mechanical properties, are not processable by most additive manufacturing techniques,
as they are prone to hot cracking.
[0010] Additive manufacturing is a manufacturing concept that brings together a series of
manufacturing technologies based on the deposition of material layer after layer,
which allows solid three-dimensional objects to be produced. In contrast to traditional
metal manufacturing techniques (subtractive techniques), this set of techniques has
properties intrinsic to the production process that affect the final properties of
the manufactured part. Several authors have estimated that in additive manufacturing
techniques such as L-PBF, the cooling rate of aluminium alloys can reach rates of
between 1.25 × 10
6 °C/s and 6.17 × 10
6 °C/s
[Li, Y et al., Mater. Des. 2014, 63, 856-867]. Furthermore, there are also some conventional techniques for the production of
parts such as HPDC that can reach up to 75 °C/s
[Karkkainen, M et al., Miner. Met. Mater. Ser. 2017, Part F6, 457-464], and, therefore, they can also present hot cracking problems.
[0011] The susceptibility to hot cracking of precipitation hardenable alloys leads to the
need for new aluminium alloys specifically designed to be able to be processed under
the working conditions of rapid solidification manufacturing techniques. For example,
7XXX series commercial alloys present problems upon being processed by WAAM and L-PBF:
alloys manufactured by WAAM present gas pores
[Köhler, M et al.; Metals (Basel). 2019, 9, 5;
Sokoluk, M et al.; Nat. Commun. 2019, 10 (1); Eimer, E et al., Weld. World 2020, 64, 1313-1319], and alloys processed by L-PBF present hot cracking
[Aversa, A et al., Materials (Basel), 2019, 12;
DebRoy, T et al., Prog. Mater. Sci. 2018, 92, 112-224;
Galy, C et al.; Addit. Manuf. 2018, 22, 165-175], deteriorating their mechanical properties.
[0012] Hot cracking arises because high cooling rates generate local stresses on a microstructural
level during aluminium solidification that cause the occurrence of microcracks and
affect the final mechanical properties. This effect is most evident in precipitation
hardenable alloys, for example, those belonging to the 2xx.x (Al-Cu) or 7xx.x (Al-Zn)
series. Hot cracking has meant that there are few aluminium alloys that can be processed
by quenching techniques. The most used series to date are of the AISi12 or AlSi10Mg
type, which are alloys developed for casting. This is because the eutectic or near-eutectic
(Al-Si) composition of these alloys allows the solidification range to be reduced,
decreasing susceptibility to hot cracking. These alloys are mostly made up of an aluminium
matrix, reinforced by eutectic Si. The mechanical properties of these alloys, such
as hardness or strength, are considerably lower than the properties of alloys of the
2xx.x (Al-Cu) or 7xx.x (Al-Zn) series or of precipitation hardenable alloys.
[0013] There are cases of specific commercial alloys designed for additive manufacturing
that are resistant to hot cracking with high mechanical properties, for example, Scalmalloy
® and A20X
™, that have been able to be processed by different additive manufacturing techniques
such as L-PBF and/or L-DED. These alloys owe a large part of their properties to the
high presence of expensive elements such as Sc, Cu and Ag in their composition.
[0014] In the state of the art, there are also published studies and results about attempts
to obtain improved aluminium alloys. For example, disclosed in patent application
US 2011/0044843 A1 are alloys that were resistant to hot cracking when manufactured by additive manufacturing;
to obtain a hardness between 165 HV and 184 HV, they had to be subjected to a T7 heat
treatment. The disclosed and studied alloys can be divided into two families: Al-Cu-Mg-Zn-Zr
and Al-Cu-Mg-Ag-Zr-Er-Y-Yb.
Summary of the invention
[0015] The present invention relates to new alloys, with a unique and determined chemical
composition, which have a low susceptibility to hot cracking and porosity, and high
hardness, without the need for heat treatments. These are high-strength alloys and
can be processed by techniques that involve solidification with quenching (> 50 °C/s),
without crack formation.
[0016] Specifically, the present invention relates to aluminium alloys, characterised in
that they comprise:
- between 4.4 and 5.3% by weight of zinc,
- between 1.7 and 1.9% by weight of copper,
- between 1.5 and 2.1% by weight of magnesium,
- between 2 and 12% by weight of silicon, and
- balance of aluminium up to 100% by weight.
[0017] It additionally relates to the use of such aluminium alloys for the preparation of
an article by near net shape manufacturing techniques.
[0018] Likewise, the invention relates to an article comprising an aluminium alloy as defined
above, or consisting of same.
Description of the figures
[0019]
Figure 1: Cross-section of the reference alloy and alloys manufactured by WAAM.
Figure 2: Micrograph of the microstructure of the alloy with 7.0% Si by WAAM.
Figure 3: Cross-section of the molten bath or melt pool of the alloys object of this invention
and reference alloys manufactured by L-DED.
Figure 4: Detail of the microstructure of reference alloy AlZn5.5MgCu processed by laser with
defects and transgranular cracks.
Figure 5: Micrograph showing the surface area of the α-Al matrix and the eutectic region.
Figure 6: Representation of the solidification curves of some alloys according to the present
invention, using the Thermo-Calc software Scheil-Gulliver model, and reference alloys.
Figure 7: Solidification curves of some alloys according to the present invention and of alloy
AlZn5.5MgCu, in the critical solidification range.
Description of the invention
[0020] The present invention relates to new alloys, with a unique and determined chemical
composition, which have a low susceptibility to hot cracking and porosity, and high
hardness, without the need for heat treatments. These are high-strength alloys and
can be processed by techniques that involve solidification with quenching (> 50 °C/s),
without crack formation.
[0021] These new alloys are a multicomponent aluminium alloy, with nominal formula AIZn4.9Cu1.8Mg2.1
and a silicon (Si) content between 2 and 12% by weight, preferably between 2.4 and
7.1% by weight, for example, 2.4, 3.9 or 7.03% by weight of silicon.
[0022] In that sense, according to a first object, the present invention relates to an aluminium
alloy, characterised in that it comprises:
- between 4.4 and 5.3% by weight of zinc,
- between 1.7 and 1.9% by weight of copper,
- between 1.5 and 2.1% by weight of magnesium,
- between 2 and 12% by weight of silicon, and
- balance of aluminium up to 100% by weight.
[0023] The aluminium alloy according to the invention may further contain one or more of:
between 0.003 and 1.0% by weight of boron;
between 0.08 and 0.3% by weight of titanium;
between 0.1 and 0.4% by weight of manganese;
between 0.1 and 0.3% by weight of chromium;
up to 1.0% by weight of silver;
between 0.01 and 0.02% by weight of nickel;
up to 0.01% by weight of zirconium.
[0024] According to a particular embodiment of the invention, the aluminium alloy comprises:
- 4.9% by weight of zinc,
- 1.8% by weight of copper,
- 2.1% by weight of magnesium,
- between 2 and 12% by weight of silicon.
[0025] According to particular embodiments of the invention, the silicon content is between
2.4 and 7% by weight, or between 2.4 and 4.9% by weight, or between 4.9 and 7% by
weight, or between 4.9 and 12% by weight, or between 7 and 12% by weight.
[0026] Another object according to the present invention is the use of an aluminium alloy
as defined above for the preparation of an article by near net shape manufacturing
techniques. These techniques can be selected from additive manufacturing, forging,
welding and casting, although they are not limited to the above.
[0027] The invention also relates to an article comprising or consisting of an aluminium
alloy as defined above.
[0028] Such a casting article is preferably selected from casings and structures for mobile
telephones (including smartphones) and laptop computers, engine blocks in vehicles,
such as automobiles, gearbox housings in vehicles, for example, aircraft, vehicle
tyres, seat frames in vehicles, such as aircraft, battery boxes for electric vehicles,
etc.
[0029] The multicomponent aluminium alloys of the present invention have the following features:
- reduced solidification range (< 40 °C), when the solid fraction (fs) is close to 1
- precipitation of eutectic compounds (between 10 and 30% of the volume of the microstructure)
- fine microstructure (SDAS < 20 µm; SDAS = secondary dendrite arm spacing
- high hardness without the need for heat treatment (> 110 HV)
- less susceptibility to hot cracking and porosity formation
[0030] As will be further illustrated in the Examples, the multicomponent aluminium alloys
according to the present invention present optimised solidification curves to reduce
susceptibility to hot cracking, and the reduction of the
solidus temperature to improve their fluidity during the last stage of solidification. The
particular compositions of these alloys have allowed a eutectic microstructure to
form, maintaining the hardness of high-strength commercial alloys.
[0031] It should be noted that among the composition of these alloys there are no critical,
expensive or hazardous elements frequently present in other alloys of the state of
the art, such as, for example, Sc, Be, Li, Y, etc., and that the high hardness of
the alloys has been achieved without the need for subsequent heat treatments.
[0032] Although the alloys according to the present invention are qualitatively based on
Al-Zn-Mg-Cu (7xxxx series) type alloys, they differ quantitatively from any existing
alloy. The alloys according to the present invention include a high amount of silicon,
unlike the norm for the alloy
[0033] AlZn5.5MgCu, a very common alloy of the Al-Zn-Mg-Cu type alloys and used as a reference
in the Examples. In Figures 6 and 7, the difference can be seen in the curves of susceptibility
to cracking on the solidification between the AlZn5.5MgCu alloy and the alloys according
to the present invention. This difference in the curve is due to the compositional
chemical difference of the alloys.
[0034] Apart from the advantages of a reduced susceptibility to cracking and porosity of
the alloys according to the present invention when they are manufactured by technologies
that involve solidifications with quenching, their fine microstructure and hardness,
it has surprisingly been found that the alloys do not form intermetallic compounds,
especially compounds with acicular morphology. Usually, the increase in the number
of elements in aluminium alloys leads to the occurrence of intermetallic compounds.
Increasing the number of elements in aluminium alloys usually promotes the precipitation
of compounds of this type; for example, in the case of aluminium alloys made up of
Si, there is typically a formation of ternary compounds with acicular morphology of
the Al-(Fe, Mn, Ni, etc.)-Si type, which are considered detrimental to the properties
of the final alloy, and could affect the fineness of the grain. The formation of intermetallic
compounds during the last stages of solidification would increase the susceptibility
to hot cracking of alloys, a phenomenon that has been prevented with the alloys of
the present invention.
[0035] Likewise, the alloys according to the present invention have surprisingly been found
to have a high tolerance to contaminating elements.
[0036] Another surprising result is the occurrence of few phases in the final structure:
obtaining a structure formed mainly by two phases, an α-Al matrix and an interdendritic
space formed by a Si eutectic, has been detected. What would be typical is that, by
applying the Gibbs phase rule, an alloy made up of N elements could have up to N +
1 phases. The stabilisation of a greater number of phases, especially if transition
metals are used in aluminium alloys, is the most typical
[Sanchez, J.M. et al., Metals (Basel). 2018, 8, 167; Sanchez, J.M. et al., Sci. Rep. 2019, 9, 6792; Sanchez, J.M. et al., J. Mater. Res. Technol. 2018, 1-9].
Examples
[0037] The following examples serve to further describe and illustrate the present invention,
but in no way should they be construed as limiting the scope of the invention.
Example 1 - Preparation of alloys according to the invention.
[0038] Alloys have been prepared according to the invention, which alloys have the following
elemental composition:
Table 1
Reference |
Si |
Cu |
Mn |
Fe |
Mg |
Cr |
Ni |
Zn |
Ti |
B |
2.4-Si |
2.39 |
1.79 |
0.352 |
0.32 |
1.73 |
0.304 |
0.01 |
4.98 |
0.087 |
0.003 |
3.9-Si |
3.92 |
1.85 |
0.329 |
0.33 |
2.38 |
0.286 |
0.004 |
5.24 |
0.072 |
0.003 |
7.0-Si |
7.03 |
1.67 |
0.399 |
0.32 |
1.54 |
0.277 |
0.01 |
5.16 |
0.194 |
0.003 |
[0039] Alloys 2.4-Si, 3.9-Si and 7.0-Si defined in Table 1 have been processed using the
following manufacturing techniques: WAAM and L-DED.
EXAMPLE 1.1 - Alloys processed by WAAM
[0040] Alloys 2.4-Si, 3.9-Si and 7.0-Si have been manufactured in a WAAM TIG/MAG flexible
additive manufacturing cell at 150 Amps (150 A). Figure 1 shows micrographs of the
cross-section of the weld bead of the alloys according to the invention, as well as
of the AlZn5.5MgCu alloy, used as a reference. Al-Zn-Mg-Cu alloys are generally alloys
that present problems when processed by WAAM, due to the formation of gas pores that
deteriorate their mechanical properties [
Guo, Y et al., Virtual Phys. Prototyp. 2022, 17, 649-661]. As can be seen in Figure 1, welding defects are only observed in reference alloy
AlZn5.5MgCu. The alloys according to the present invention show a pore-free surface.
Furthermore, none of the alloys according to the invention show cracks indicating
susceptibility to cracking when processed by WAAM; however, commercial alloy AlZn5.5MgCu
used as a reference does show cracks.
[0041] Based on these images, it is shown that the alloys according to the present invention
show a fineness in their microstructure, after being processed by quenching techniques,
as well as the precipitation of eutectic compounds. By way of example, Figure 2 shows
the micrograph of the microstructure of alloy 7.0-Si. It is observed that said alloy
is made up of an aluminium matrix, with a mean SDA spacing less than 8 µm in all cases,
with the precipitation of fine eutectic compounds. In the microstructure, only the
Al and Si eutectic can be distinguished.
[0042] The mean SDA values of the alloys according to the present invention are indicated
in Table 2:
Table 2. SDA values of the alloys according to the invention
Ref. |
SDAS (µm) - 150 A |
2.4% Si |
5-8 |
3.9% Si |
5-7 |
7.0% Si |
4-8 |
EXAMPLE 1.2 - Alloys processed by L-DED
[0043] Alloys 2.4-Si, 3.9-Si and 7.03-Si have been manufactured by laser directed energy
deposition or L-DED technology. Two reference alloys have also been processed, the
alloy AISi10Mg and AlZn5.5MgCu, respectively, with zero and high susceptibility to
hot cracking. Micrographs of the cross-section of the melt pool of the alloys object
of this invention and of the reference alloys are shown in Figure 3. As can be observed
in the figure, all the samples corresponding to the alloys according to the present
invention have a crack-free surface.
[0044] In contrast, laser-processed reference alloy AlZn5.5MgCu shows microporosity and
crack defects, as can be seen in Figure 4, where the cracks are shown in detail, in
different regions of the melt area.
[0045] In contrast, Figure 4 shows the micrograph of the microstructure of the alloy with
7.0% Si. The alloy is made up of an aluminium matrix with a mean SDA spacing less
than 4 µm in all cases, with the precipitation of fine eutectic compounds. Only the
Al and Si eutectic (fine eutectic compounds) is distinguished.
[0046] The mean SDA values of the alloys studied in this Example 1.2 are summarised in Table
3:
Table 3. SDA values of the alloys studied in this example.
Ref. |
SDAS (µm) - L-DED |
2.4% Si |
3-4 |
3.9% Si |
3-4 |
7.0% Si |
3-4 |
[0047] Therefore, it is shown that the alloys according to the present invention have a
fine microstructure reinforced with eutectic compounds in the interdendritic space,
which has allowed all alloys to be manufactured without hot cracking problems.
Example 2 - Hardness
[0048] The hardness of the alloys has been measured according to the ISO 6507-1 "Metallic
Materials - Vickers Hardness Test" standard and has been compared with reference alloys
AISi10Mg and AlZn5.5MgCu manufactured by the traditional method with moderate cooling
and by additive manufacturing with quenching. To obtain the hardness values, an FV-700
model durometer (Future-Tech, Kawasaki, Japan) under the load of 10 kgf has been used.
At least five random surface hardness measurements have been taken on each sample,
with a retention time of the indenter in the tested sample of 10 s.
[0049] All the alloys object of this invention have obtained a hardness higher than that
of reference alloy AlSi10Mg and higher than that of reference alloy AlZn5.5MgCu when
manufactured by additive manufacturing. Alloy AlZn5.5MgCu has been shown to be susceptible
to hot cracking when manufactured by additive manufacturing, with the occurrence of
cracks that have decreased the hardness of the alloy. The hardness of this alloy is
145 HV 10 in its commercial forging format, these values being similar to those that
can be attained with the addition of 7.0% Si.
[0050] Therefore, a combination of the solidification and microstructural properties of
alloy AISi10Mg with the hardness properties of alloy AlZn5.5MgCu has been obtained.
It should be noted that, like alloy AISi10Mg, the hardness of the alloys object of
the invention have increased when manufactured by additive manufacturing with respect
to that obtained by conventional manufacturing methods, as opposed to what happens
with alloy AlZn5.5MgCu.
[0051] The hardness values obtained are indicated in Table 4:
Table 4. Hardness of the preferred alloys of the present invention and reference alloys.
Alloy |
WAAM Hardness (HV10) |
L-DED Hardness (HV10) |
As cast Hardness (HV 10) |
IACS(4)(%) |
AISi10Mg |
95 ± 10 |
93 ± 08 |
66 ± 02 |
31 |
AISi10Mg-T6 [C] |
-- |
105 |
-- |
-- |
6061-T6 [C] |
-- |
124 |
-- |
-- |
7050-T7 [C] |
-- |
172 |
-- |
-- |
AlZn5.5MgCu(1 ) |
(3) |
119 ± 02 |
131 ± 09 |
22 |
AlZn5.5MgCu(2 ) |
(3) |
129 ± 02 |
145 ± 01(2) |
-- |
2.4% Si |
127 ± 04 |
111 ± 02 |
105 ± 10 |
22 |
3.9% Si |
156 ± 04 |
137 ± 03 |
114 ± 01 |
21 |
7.0% Si |
126 ± 14 |
141 ± 06 |
131 ± 09 |
20 |
1 as cast
2 commercial wrought alloy
3 sample with pores, could not be measured (Fig. 1)
4 IACS = International Annealed Copper Standard
[C] publication US10941473B2 |
Example 3: Solidification curves of the alloys according to the invention
[0052] Alloys susceptible to hot cracking can be identified from their solidification curves.
Generally, these alloys present large solidification ranges between liquidus and solidus
temperatures and an abrupt change or turnover in the solidification curves at high
fractions of solids. The different models for hot cracking determine that this phenomenon
occurs when the solid fraction is greater than 0.8
[Eskin, D.G. et al., Prog. Mater. Sci. 2004, 49, 629-711], and when tensile stresses exceed the resistance of the material in the semisolid
state. The abrupt change in the solidification curve is normally associated with increased
levels of solute elements that are distributed throughout the liquid to a high degree
during solidification. The decreased solid fraction (f
s) at which the reduction of the difference between the solidus and liquidus temperatures
occurs decreases the tendency for hot cracking in alloys
[Martin, J.H. et al., Nature 2017, 549, 365-369]. In Figure 6, the solidification curves of alloys according to the present invention
have been represented, using the Thermo-Calc software Scheil-Gulliver model, specifically
for the following alloys:
- 1. AIZn4.9Cu1.8Mg2.1Si2.4 2.4% Si
- 2. AIZn4.9Cu1.8Mg2.1Si3.9 3.9% Si
- 3. AIZn4.9Cu1.8Mg2.1Si7.0 7.0% Si
[0053] The graph also includes two reference alloys, alloy AISi10Mg (ENAC-43000) since it
is representative of alloys not susceptible to cracking, and alloy AlZn5.5MgCu (AA7075)
since it is a precipitation hardenable alloy susceptible to hot cracking. Lastly,
the composition of the designed alloy has also been calculated, but without Si (0%
Si). As can be seen, alloy 0% Si presents a solidification curve similar to alloys
susceptible to hot cracking, with a sharp turnover in the last stages of solidification.
However, it does represent a notable improvement over AlZn5.5MgCu.
[0054] As can be observed, the effects of Si cause the curve to gradually flatten, in addition
to the turnover moving back towards a solid fraction closer to that of alloy AISi10Mg.
Furthermore, with the incorporation of more than 2.4% of Si, there is a drop in the
solidus temperature, which improves the fluidity of the material during solidification.
Example 4: Critical solidification range
[0055] A more specific and complementary way to quantify the susceptibility to hot cracking
of aluminium alloys is to represent the diagrams as a function of temperature and
the square root of the solid fraction (T ° VS

) in a certain range, called the critical solidification range. In Figure 7, the slope
of the alloys object of the present invention has been quantified. A smaller slope
indicates a lower susceptibility to hot cracking.
[0056] To that end, alloys can be evaluated by means of the index for the susceptibility
of an alloy to hot cracking during the last stage of solidification by
[Kou, S., Acta Mater. 2015, 88, 366-374]:

when

is close to 1
[0057] More in detail, the critical solidification range is defined when f
s is between 0.87 and 0.94, in other words, when

is between 0.933 and 0.970.
[0058] The largest slope, therefore, the highest tendency to hot cracking, is held by alloy
AlZn5.5MgCu, followed by alloy 0% Si (AIZn4.9Cu1.8Mg2.1), and finally, with a similar
susceptibility, alloys 2.4% Si, 3.9% Si and 7.0% Si. The representative points of
the solidification curves according to the criterion used for the design of the alloys
are summarised in Table 5. As can be seen, the solidification range of the alloys
object of this invention has been reduced to one third with respect to that of the
alloy used as a reference alloy susceptible to cracking.
Table 5. Representative points of the solidification curves
Alloy |
T ° to (Fs)1/2= 0.933 |
T ° to (Fs)1/2 = 0.970 |
Critical range (°C) |
AlZn5.5MgCu |
562 |
471 |
90 |
0% Si |
541 |
469 |
55 |
2.4% Si |
511 |
474 |
37 |
3.9% Si |
518 |
485 |
33 |
7.03% Si |
518 |
485 |
33 |
Example 5: Microstructure of an alloy according to the invention processed by computational
digital image analysis techniques
[0059] By way of example, Figure 5 shows the microstructure processed by computational digital
image analysis techniques of the alloy with 7.03% Si. The surface of the α-Al matrix,
which represents a minimum of 75% in the invention, is observed in light grey. The
interdendritic region, which is made up of eutectic compounds, which is a maximum
of 25% in the alloy of the present invention, is observed in black.
1. An aluminium alloy,
characterised in that it comprises:
- between 4.4 and 5.3% by weight of zinc,
- between 1.7 and 1.9% by weight of copper,
- between 1.5 and 2.1% by weight of magnesium,
- between 2 and 12% by weight of silicon, and
- balance of aluminium up to 100% by weight.
2. The aluminium alloy according to claim 1, characterised in that it further comprises between 0.003 and 1.0% by weight of boron.
3. The aluminium alloy according to any one of claims 1 and 2, characterised in that it further comprises between 0.08 and 0.3% by weight of titanium.
4. The aluminium alloy according to any one of claims 1 to 3, characterised in that it further comprises between 0.1 and 0.4% by weight of manganese.
5. The aluminium alloy according to any one of claims 1 to 4, characterised in that it further comprises between 0.1 and 0.3% by weight of chromium.
6. The aluminium alloy according to any one of claims 1 to 5, characterised in that it further comprises up to 1.0% by weight of silver.
7. The aluminium alloy according to any one of claims 1 to 6, characterised in that it further comprises between 0.01 and 0.02% by weight of nickel.
8. The aluminium alloy according to any one of claims 1 to 7, characterised in that it further comprises up to 0.01% zirconium.
9. The aluminium alloy according to any one of claims 1 to 8,
characterised in that it comprises
4.9% by weight of zinc,
1.8% by weight of copper,
2.1% by weight of magnesium,
between 2 and 12% by weight of silicon.
10. The aluminium alloy according to any one of claims 1 to 9, characterised in that it comprises between 2.4 and 7% by weight of silicon.
11. Use of an aluminium alloy as defined in any one of claims 1 to 10 for the preparation
of an article by near net shape manufacturing techniques.
12. The use of an aluminium alloy according to claim 11, wherein the manufacturing technique
without the need for subsequent cuts is selected from additive manufacturing, linear
and rotary friction welding, pressure die casting, sand casting, investment casting
or injection moulding.
13. An article comprising an aluminium alloy as defined in any one of claims 1 to 10.
14. An article consisting of an aluminium alloy as defined in any one of claims 1 to 10.
15. The article according to claim 13 or 14, selected from casings and structures for
mobile telephones and laptop computers, engine blocks in automobiles, gearbox housings,
vehicle tyres, seat frames in vehicles, battery box for electric vehicles.