Metallic glasses having a combination of high permeability, low coercivity, low AC core loss, low exciting power and high thermal stability

Abstract

 Metallic glasses having high permeability, low magnetostriction, low coercivity low ac core loss, low exciting power and high thermal stability are disclosed. The metallic glasses consist essentially of about 66 to 82 atom percent iron, from 1 to about 8 atom percent of said iron being, optionally replaced with nickel and/or cobalt, about 1 to 6 atom percent of at least one element selected from the group consisting of chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and hafnium, about 17 to 28 atom percent of boron, 0.5 to 6 atom percent of said boron being, optionally, replaced with silicon and up to 2 atom percent of boron being, optionally, replaced with carbon, plus incidental impurities. Such metallic glasses are especially suited for use in tape heads, relay cores, transformers and the like.

Description

Field of the Invention

[0001] The invention relates to metallic glasses having high permeability, low magnetostriction, low coercivity, low ac core loss, low exciting power and high thermal stability.

Description of the Prior Art

[0002] As is known, metallic glasses are metastable materials lacking any long range order. X-ray diffraction scans of glassy metal alloys show only a diffuse halo similar to that observed for inorganic oxide glasses.

[0003] Metallic glasses (amorphous metal alloys) have been disclosed in U.S. Patent 3,856,513, issued December 24, 1974 to H.S. Chen et al. These alloys include compositions having the formula M_aY_bZ_c, where M is a metal selected from the group consisting of iron, nickel, cobalt, vanadium and chromium, Y is an element selected from the group consisting of phosphorus, boron and carbon and Z is an element selected from the group consisting of aluminum, silicon, tin, germanium, indium, antimony and beryllium, "a" ranges from about 60 to 90 atom percent, "b" ranges from about 10 to 30 atom percent and "c" ranges from about 0.1 to 15 atom percent. Also disclosed are metallic glassy wires having the formula T_iX_j' where T is at least one transition metal and X is an element selected from the group consisting of phosphorus, boron, carbon, aluminum, silicon, tin, germanium, indium, beryllium and antimony, "i" ranges from about 70 to 87 atom percent and "j" ranges from about 13 to 30 atom percent. Such materials are conveniently prepared by rapid quenching from the melt using processing techniques that are now well-known in the art.

[0004] Metallic glasses are also disclosed in U.S. Patent No. 4,067,732 issued January 10, 1978. These glassy alloys include compositions having the formula M_aM'_bCr_cM"_dB_e, where M is one iron group element (iron, cobalt and nickel), M' is at least one of the two remaining iron group elements, M" is at least one element of vanadium, manganese, molybdenum, tungsten, niobium and tantalum, B is boron, "a" ranges from about 40 to 85 atom percent, "b" ranges from 0 to about 45 atom percent, "c" and "d" both range from 0 to about 20 atom percent and "e" ranges from about 15 to 25 atom percent, with the provision that "b", "c" and "d" cannot be zero simultaneously. Such glassy alloys are disclosed as having an unexpected combination of improved ultimate tensile strength, improved hardness and improved thermal stability.

[0005] These disclosures also mention unusual or unique magnetic properties for many metallic glasses which fall within the scope of the broad claims. However, metallic glasses possessing a combination of higher permeability, lower magnetostriction, lower coercivity, lower core loss, lower exciting power and higher thermal stability than prior art metallic glasses are required for specific applications such as tape recorder head, relay cores, transformers and the like.

SUMMARY OF THE INVENTION

[0006] In accordance with the invention, metallic glasses having a combination of high permeability, low magnetostriction, low coercivity, low ac core loss, low exciting power and high thermal stability are provided. The metallic glasses consist essentially of about 66 to 82 atom percent of iron, from 1 to about 8 atom percent of which metal may be replaced with at least one of nickel and cobalt, about 1 to about 6 atom percent of at least one element selected from the group consisting of chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and hafnium, about 17 to 28 atom percent of boron, from 0.5 to about 6 atom percent of boron being, optionally, replaced with silicon and up to about 2 atom percent of boron being, optionally, replaced with carbon, plus incidental impurities. The metallic glasses of the invention are suitable for use in tape recorder heads, relay cores, transformers and the like.

DETAILED DESCRIPTION OF THE INVENTION

[0007] The metallic glasses of the invention are characterized by a combination of high permeability, low saturation magnetostriction, low coercivity, low ac core loss, low exciting power and high thermal stability. The glassy alloys of the invention consist essentially of about 66 to 82 atom percent iron, from 1 to about 8 atom percent of which metal may be replaced with at least one of nickel and cobalt, about 1 to 6 atom percent of at least one element selected from the group consisting of chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and hafnium, about 17 to 28 atom percent of boron, from 0.5 to about 6 atom percent of which metalloid may be replaced with silicon and up to 2 atom percent of which metalloid may be replaced with carbon, plus incidental impurities. A concentration of less than about 1 atom percent of Cr, Mo, W, V, Nb, Ta, Ti, Zr and/or Hf does not result in sufficient improvement of the properties of permeability, saturation magnetostriction, coercivity, ac core loss and thermal stability. A concentration o greater than about 6 atom percent of at least one of these elements results in an unacceptably low Curie temperature.

[0008] Iron provides high saturation magnetization at room temperature. Accordingly the metal content is preferably substantially iron, with up to about 8 atom percent nickel and/or cobalt in order to compensate the reduction of the room temperature saturation magentiza- tion due to the presence of chromium, molybdenum, tungsten, niobium, tantalium, titanium, zirconium and/or hafnium. The addition of nickel increases permeability.

[0009] Examples of metallic glasses of the invention include Fe₈₀Ni₁Mo₁B₁₆Si₂, Fe₇₆Ni₄Mo₂B_17.5Si_0.5 Fe₇₅ Ni₂Co₂Mo₃B₁₆Si₂, F₇₅Co₄Mo₃B₁₆Si₂, Fe75Ni4Mo3B16Si2, Fe₇₇Ni₂Mo₃B₁₆Si₂, Fe₇₅Ni₄Mo₃B₁₄Si₄, Fe₇₁Ni₄Mo₃B₁₇Si₅, Fe₇₄Ni₄Mo₄B₁₆Si₂, Fe₇₀Ni₆Mo₆B₁₅Si₃, Fe₇₅Ni₄V₃B₁₄Si₂C₂, Fe₇₁Ni₄Mo₃B₁₆Si₄C₂, Fe78Ni2Mo2B12Si4C2, Fe₇₈Ni₂Cr₂B₁₆Si₂, Fe₇₅Ni₄Nb₃B₁₆Si₂, Fe₇₅Ni₄W₃B₁₆Si₂, Fe75Ni4V3B16Si2' Fe₇₉Ni₄Ta₁B₁₆Si₂, Fe₇₅Ni₄Ti₃B₁₆Si₂, Fe₇₅Ni₄Zr₃B₁₆Si₂, Fe₇₉Ni₄Hf₁B₁₆Si₂, Fe₇₂Ni₂Mo₂B₂₂Si₂, Fe₇₀Ni₂Mo₂B₂₂Si₄, and Fe₇₀Ni₂Mo₂B₂₄Si₂ (the subscripts are in atom percent). The purity of all alloys is that found in normal commercial practice.

[0010] The presence of chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and/or hafrium raises the crystallization temperature while simultaneously lowering the Curie temperature of the glassy alloy. The increased separation of these temperatures provides ease of magnetic annealing, that is, thermal annealing at a temperature near the Curie temperature. As is well-known, annealing a magnetic material close to its Curie temperature generally results in improved properties. As a consequence of the increase in crystallization temperature with increase in the concentration of chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium, and/or hafnium, annealing can be easily accomplished at elevated temperatures near the Curie temperature and below the crystallization temperature. Such annealing cannot be carried out for many alloys similar to those of the invention but lacking these elements. On the other hand, too high a concentration of chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and/or hafnium reduces the Curie temperature to a level that may be undesirable in certain applications. For metallic glasses in which boron and silicon are the major and minor metalloid constituents respectively, a preferred range of chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and/or hafnium concentration is about 2 to 4 atom percent.

[0011] It is preferred that the metalloid content consist essentially of (1) substantially boron with a small amount of silicon, (2) boron plus silicon and (3) boron and silicon plus a small amount of carbon. Preferably, the metalloid content ranges from about 17 to 28 atom percent for maximum thermal stability.

[0012] Preferred metallic glass systems are as follows:

1. Fe-M-Mo-B-Si: Fe_100-a-b-c-dM_aMo_bB_cSi_d, where ^M is at least one of nickel and cobalt. When (c+d) is about 18, the preferred ranges of a,b,c and d are from about 2 to 8, from about 1 to 4, from about 14 to 17.5 and from about 0.5 to 4, respectively. When (c+d) is about 22, the preferred ranges for a,b,c and d are from about 2 to 8, from about 1 to 6, from about 15 to 20.5 and from about 0.5 to 6, respectively. When (c+d) is close to 25, the preferred ranges of a, b, c and d are from about 2 to 8, from about 1 to 6, from about 21 to 25 and from about 1 to 6 respectively. These metallic glasses have a combination of saturation induction (B_s) of 1.0-1.4 Tesla, saturation magnetostriction (^À_s) between 12 and 24 ppm, Curie temperature (^e_f) between about 475 and 705 K and first crystallization temperature of 750-880 K. When optimally heat-treated, these alloys have excellent ac magnetic properties especially at high frequencies (f>10³ Hz). The ac core loss (L) and exciting power (P ) taken at f = 50 kHz^fand the induction level of B_m = 0.1 Tesla of, for example, a heat-treated Fe₇₅Ni₄Mo₃B₁₆Si₂ metallic glass are 6.5 W/kg and 13.4 VA/kg, respectively. These values are to be compared with L = 7W/kg and P_e = 20 VA/kg for a a heat-treated prior art metallic glass of the same thickness having the composition Fe₇₉B₁₆Si₅. The permeability P at B_m = 0.01 Tesla is 10 500 and 8000 for the heat-treated Fe₇₅Ni₃Mo₄B₁₆Si₂ and Fe₇₉B₁₆Si₅, respectively. The smaller saturation magnetostriction (λ_s) of about 20 ppm of the present alloy as compared to s λ_s = 30 ppm for the aforesaid prior art alloy makes the alloys of the present invention especially suited for magnetic device applications such as cores for high frequency transformers. Beyond f = 50 kHz, the alloys of the present invention have permeabilities comparable or higher than those for crystalline supermalloys which have B_s near 0.8 Tesla. The higher values of B for the present alloys make these alloys better suited than supermalloys for magnetic applications of f>50 kHz. Fe-^M-M'-B-Si: Fe_100-a-b-c-dM_aM'_bB_cSi_d where M is nickel and/or cobalt and M' is selected from Cr, W, V, Nb, Ta, Ti, Zr or Hf. When (c+d) is about 18, the preferred ranges of a,b,c and d are about 2 to 8, from about 1 to 4, from about 14 to 17.5 and from about 0.5 to 4, respectively. When (c+d) is about 22, the preferred ranges for a,b,c and d are from about 2 to 8, from about 1 to 6, from about 16 to 21.5 and from about 0.5 to 6, respectively. When (c+d) is close to 25, the preferred ranges for a, b, c and d are from about 2 to 8, from about 1 to 6, from about 21 to 25 and from about 1 to 6 respectively. Fe-M-M'-B-Si-C: Fe_{100-a-b-c-d-e}M _aM'_bB_cSi_dC_e wherein M is nickel and/or cobalt, and M' is selected from the group consisting of Cr, Mo, W, V, Nb, Ta, Ti, Zr or Hf. When (c+d) is about 18, the preferred ranges for a,b,c,d and e are from about 2 to 8, from about 1 to 4, from about 12 to 17.5, from about 0.5 to 4 and from 0 to 2, respectively. When (c+d) is about 22, the preferred ranges for a,b,c,d and e are from about 2 to 8, from about 1 to 6, from about 14 to 21.5, from about 0.5 to 6 and from about 0 to 2, respectively. When (c+d) is close to 25, the preferred ranges for a, b, c, d and e are from about 2 to 8, from about 1 to 6, from'about 20 to 27, from about 1 to 6 and from about 0 to 2 respectively.

[0013] Magnetic permeability is the ratio of induction to applied magnetic field. A higher permeability renders a material more useful in certain applications such as tape recorder heads, due to the increased response. The frequency dependence of permeability of the glassy alloys of the invention is similar to that of the 4-79 Permalloys in the medium-to-high frequency range (1-50 kHz), and at higher frequencies (about 50 kHz to 1 MHz), the permeability is comparable to that of the supermalloys. Especially noted is the fact that a heat-treated Fe_7sNi₄Mo₃B₁₆si₂ metallic glass has permeability of 24,000 while the best-heat-treated prior art Fe40Ni36M04B20 metallic glass has a permeability of 14,000 at 1 kHz and the induction level of 0.01 Tesla.

[0014] Saturation magnetostriction is the change in length under the influence of a saturating magnetic field. A lower saturation magnetostriction renders a material more useful in certain application such as tape recorder heads. Magnetostriction is usually discussed in terms of the ratio of the change in length to the original length, and is given in ppm. Prior art iron with metallic glasses evidence saturation magnetostric- tions of about 30 ppm as do metallic glasses without the presence of the any of the elements belonging to the IVB, VB and VIB columns of the periodic table such as molybdenum. For example, a prior art iron rich metallic glass designated for use in high frequency applications and having the composition Fe₇₉B₁₆Si₅ has a saturation magnetostriction of about 30 ppm. In contract, a metallic glass of the invention having the composition Fe₇₅Ni₄Mo₃B₁₆Si₂ has a saturation magnetostriction of about 20 ppm. A lower saturation magnetostriction leads to a lower phase angle between the exciting field and the resulting induction. This results in lower exciting power as discussed below.

[0015] Ac core loss i's that energy loss dissipated as heat. It is the hysteresis in an ac field and is measured by the area of a B-H loop for low frequencies (less than about 1 kHz) and from the complex imput power in the exciting coil for high frequencies (about 1 kHz to 1 MHz). The major portion of the ac core loss at high frequencies arises from the eddy current generated during flux change. However, a smaller hystersis loss and hence a smaller coercivity is desirable. A lower core loss renders a material more useful in certain applications such as tape recorder heads and transformers. Core loss is discussed in units of watts/kg. Prior art heat-treated metallic glasses typically evidence ac core losses of about 0.05 to 0.1 watts/kg at an induction of 0.1 Tesla and at the frequency range of 1 kHz. For example, a prior art heat-treated metallic glass having the composition Fe40Ni36Mo4B20, has an ^ac core loss of 0.07 watts/kg at an induction of 0.1 Tesla and at the frequency of 1 kHz, while a metallic glass having the composition Fe₇₆Mo₄B₂₀ has an ac core loss of 0.08 watts/kg at an induction of 0.1 Tesla and at the same frequency. In contrast, a metallic glass alloy of the invention having the composition Fe₇₅Ni₄Mo₃B₁₆Si₂ has an ac core loss of 0.02 watts/kg at an induction of 0.1 Tesla and at the same frequency.

[0016] Exciting power is a measure of power required to maintain a certain flux density in a magnetic material. It is therefore desirable that a magnetic material to be used in magnetic devices has an exciting power as low as possible. Exciting power (P ) is related to the above-mentioned core loss (L) through the relationship L = P_e cos δ where δ is the phase shift between the exciting field and the resultant induction. The phase shift is also related to the magnetostriction in such a way that a lower magnetostriction value leads to a lower phase shift. It is then advantageous to have the magnetostriction value as low as possible. As mentioned earlier, prior art iron-rich metallic glasses such as ^Fe₇₉^B₁₆Si₅ have the magnetostriction value near 30 pp_m, in contract to the magnetostriction value of about 20 ppm of the metallic glasses of the present invention. This difference results in a considerable phase shift difference. For example, optimally annealed prior art metallic glass Fe₇₉B₁₆Si₅ has δ near 70° while the metallic glasses of the present invention have 6 near 50°. This results, for a given core loss, in a higher exciting power by a factor of two for the prior art metallic glass than the metallic glass of the present invention.

[0017] Crystallization temperature is the temperature at which a metallic glass begins to crystallize. A higher crystallization temperature renders a material more useful in high temperature applications and, in conjunction with a Curie temperature that is substantially lower than the crystallization temperature, permits magnetic annealing just above the Curie temperature. Some metallic glasses crystallize in multiple steps. In such cases, the first crystallization temperature (the lowest value of the crystallization temperatures) is the meaningful one as far as the materials' thermal stability is concerned. The crystallization temperature as discussed herein is measured by differential scanning calorimetry. Prior art glassy alloys evidence crystallization temperatures of about 660 K to 750 K. For example, a metallic glass having the compo- ^sition Fe₇₈Mo₂B₂₀ has a crystallization temperature of 680 K, while a metallic glass having the composition ^Fe₇₄^Mo₆^B₂₀ has a crystallization temperature of 750 _K. In contrast, metallic glasses of the invention evidence increases in crystallization temperatures to a level above 750 K.

[0018] The magnetic properties of the metallic glasses of the present invention are improved by thermal treatment, characterized by choice of annealing temperatures (T_a), holding time (ta), applied magnetic field (either parallel or perpendicular to the ribbon direction and in the ribbon plane), and post-treatment cooling rate. For the present alloys, the optimal properties are obtained after an anneal which causes the controlled precipitation of a certain number of crystalline particles from the glassy matrix. Under these conditions, for compositions having boron content ranging from about 17 to 20 atom percent, the discrete particles have a body-centered cubic structure. The particles are composed essentially of iron, up to 22 atom percent of the iron being adapted to be replaced by at least one of nickel, cobalt, chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium, hafnium, silicon and carbon. For compositions having boron content ranging from about 21 to 25 atom percent and iron content ranging from about 69 to 78 atom percent, the discrete particles consist essentially of a mixture of particles, a major portion of which mixture contains particles having a crystalline Fe₃B structure. The particles of such portion are composed of iron and boron, up to 14 atom percent of the iron being adapted to be replaced by at least one of nickel, cobalt, chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and hafnium and up to 2 atom percent of the boron being adapted to be replaced by carbon. A small number of such particles introduces a certain decrease in the average domain wall spacing with concomitant decrease in core loss. Too large a number of particles increases the coercivity and thus the hysteresis loss. A metallic glass of the present invention with composition Fe75Ni4Mo3B16Si2 has a combination of low loss and high permeability with a coercivity of only 2 A/m when optimally annealed. In contrast to this, an optimally annealed prior art metallic glass Fe79Bl6Sis has a coercivity of about 8 A/m. The crystalline particle size in the optimally heat-treated materials of the present invention ranges between 100 and 300nm, and their volume fraction is less than 1%. The interparticle spacing is of the order of 1-10µm.

[0019] In summary, the metallic glasses of the invention have a combination of high permeability, low saturation magnetostriction, low coercivity, low ac core loss, low exciting power and high crystallization temperature and are useful as tape heads, relay cores, transformers and the like.

[0020] The metallic glasses of the invention are prepared by cooling a melt of the desired composition at a rate of at least about 10 "C/sec, employing quenching techniques well known to the metallic glass art; see e.g., U.S. Patent 3,856,513. The metallic glasses are substantially completely glassy, that is, at least 90% glassy, and consequently possess lower coercivities and are more ductile than less glassy alloys.

[0021] A variety of techniques are available for fabricating continuous ribbon, wire, sheet, etc. Typically, a particular composition is selected, powders or granules of the requisite elements in the desired portions are melted and homogenized and the molten alloy is rapidly quenched on a chill surface such as a rapidly rotating cylinder.

EXAMPLES

Example 1: Fe-Ni-Mo-B-Si

[0022] Ribbons having compositions given by Fe_100-a-b-c-dNi_aMo_bB_cSi_d and having dimensions about 1 to 2.5 cm wide and about 25 to 50 µm thick were formed by squirting a melt of the particular composition by overpressure of argon onto a rapidly rotating copper chill wheel (surface speed about 3000 to 6000 ft/min).

[0023] Molybdenum content was varied from 1 to 6 atom percent, for which substantially glassy ribbons were obtained. Molybdenum content higher than 6 atom percent reduced the Curie temperature to an unacceptable low value.

[0024] Permeability, magnetostriction, core loss, magnetization and coercive force were measured by conventional techniques employing B-H loops, metallic strain gauges and a vibrating sample magnetometer. Curie temperature and crystallization temperature were measured respectively by an induction method and differential scanning calorimetry. The measured values at room temperature saturation induction, Curie temperature, room temperature saturation magnetostriction and the first crystallization temperature are summarized in Table I below. The magnetic properties of these glassy alloys after annealing are presented in Table II. Optimum annealing conditions for the metallic glass Fe₇₅Ni₄Mo₃B₁₆Si₂ and the obtained results are summarized in Table III. Frequency dependence of permability and ac core loss of this optimally annealed alloy are listed in Table IV.

[0025] The presence of molybdenum is seen to increase the permeability and the crystallization temperature and to lower the ac core loss, exciting power and magnetostriction. Especially noted is the fact that the optimally heat-treated metallic glass Fe_7SNi₄M0₃^B₁₆^Si₂ of the present invention has a coercivity reaching as low as 2.5 A/m and yet has a low core loss of 6.5 w/kg and permeability of 12500 at 50 kHz and at the induction level of 0.1 Tesla. The combination of these properties make these compositions suitable for high frequency transformer and tape-head applications.

Example 2: Fe-Ni-M-B-Si System

[0026] Ribbons having compositions given by Fe_100-a-b-c-dM-M'-B-Si when M is nickel and/or cobalt, M' is one of the elements chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and hafnium, and having dimensions about 1 cm wide and about 25 to 50Pm thick were formed as in Example 1.

[0027] Metal "M'" content was varied from 1 to 6 atom percent, for which substantially glassy ribbons were obtained. Higher metal "M'" content reduced the Curie temperature to an unacceptably low value.

[0028] The magnetic and thermal data are summarized in Table V below. The magnetic properties of these glassy alloys after annealing are presented in Table VI.

[0029] Low field magnetic properties of these metallic glasses were comparable to those for the metallic glasses containing molybdenum (Example 1).

[0030] A combination of low ac core loss and high permeability at high frequency is achieved in the metallic glasses of the present invention. The thermal stability is also shown to be excellent as evidenced by high crystallization temperature. These improved combination of properties of the metallic glasses of the present invention renders these compositions suitable in the magnetic cores of transformers, tape-recording heads and the like.

[0031] Table V. Examples of the room temperature saturation induction, B_s, Curie temperature, θ_f, saturation magnetostriction, X_s, and the first crystallization temperature, Tc, for the metallic glasses having the composition Fe_100-a-b-c-dM_aM'_bB_cSi_d where M is at least one of nickel and cobalt, and M' = Cr, Mo, W, V, Nb, Ta, Ti, Zr or Hf.

[0032] Table VI. Core loss (L), exciting power (P_e) and permeability (µ) taken at f = 50 kHz, and B_m= 0.1 Tesla on the heat-treated metallic glasses having the composition Fe_100-a-b-c-dM_aM'_bB_cSi_d where M = Ni, and/or Co, and M' = Cr, Mo₁, W, V, _Nb, Ta, Ti, Zr or Hf. The annealing temperatures are indicated by T_a and the holding time is 15 min. for allthe materials.

[0033] Table VII. Saturation induction (Bs), Curie temperature (θ_f), stauration magnetostriction (λ_s) and the first crystallization temperature (T_cl) of the metallic glasses having the composition Fe_{100-a-b-c-d-e}Ni_aM_bB_cSi_dC_e Where M' = Cr, Mo, W, V, Nb, Ta, Ti, or Zr.

Example 3: Fe-Ni-M-B-Si-C System

[0034] Ribbons having compositions given by Fe_{100-a-b-c-d-e}Ni_aM'_bB_cSi_dC_e where M = Cr, Mo, W, V, _Nb, Ta, Ti, or Zr and having dimensions about 1 cm wide and about 25 to 50 µm thick were formed as in Example 1. The metal "M'" content was varied from 1 to 6 atom percent, and the carbon content "e" was up to 2 atom percent for which substantially glassy ribbons were obtained. The metal "M'" content greater than about 6 atom percent reduced the Curie temperature to an unacceptably low value.

[0035] The magnetic and thermal data are summarized in Table VII below. The magnetic properties of these metallic glasses after annealing are presented in Table VIII. A combination of low ac core loss, high permeability, and high thermal stability of the metallic glasses of the present invention renders these compositions suitable in the magnetic cores of transformers, recording heads and the like.

[0036] Table VIII. Core loss (L), exciting power (P_e) and permeability (µ) taken at f = 50 kHz and B = 0.1 Tesla on the heat-treated metallic glasses having the composition Fe_{100-a-b-c-d-e}Ni_aM'_bB_cSi_dC_e where ^M' = Cr, Mo, W, V, Nb or Ta. Annealing temperatures are indicated by T_a and the holding time is 15 min. for all the materials.

[0037] Having thus described the invention in rather full detail, it will be understood that this detail need not be strictly adhered to but that various changes and modifications may suggest themselves to one skilled in the art, all falling within the scope of the present invention as defined by the subjoined claims.

Claims

1. A metallic glass that is substantially completely glassy having a combination of high permability, low magnetostriction, low coercivity, low ac core loss, low exciting power and high thermal stability consisting essentially of 66 to 82 atom percent of iron, from 1 to 8 atom percent of said iron being, optionally, replaced with at least one element selected from the group consisting of nickel, cobalt and mixtures thereof, 1 to 6 atom percent of at least one element selected from the group consisting of chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and hafnium, 17 to 28 atom percent of boron, from 0.5 to 6 atom percent of said boron being, optionally, replaced with silicon and up to 2 atom percent of boron being, optionally, replaced with carbon, plus incidental impurities.

2. The metallic glass of claim 1, in which the metal consists essentially of 62 to 79 atom percent iron, 2 to 8 atom percent of at least one element selected from the group consisting of nickel, cobalt and mixtures thereof, and 2 to 4 atom percent of at least one element selected from the group consisting of chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and hafnium.

3. The metallic glass of claim 1, in which the replacement of boron with silicon and carbon provides said glass with a metalloid element selected from the group consisting of substantially boron and from .5 to 4 atom percent silicon, and boron plus silicon together with from 0 to 2 atom percent carbon.

4. The metallic glass of claim 3, in which said metalloid element ranges from 17 to 26 atom percent.

5. The metallic glass of claim 1, consisting essentially of 70 to 79 atom percent iron, about 2 to 4 atom percent of at least one element selected from the group consisting of nickel, cobalt and mixtures thereof, 2 to 4 atom percent of an element selected from the group consisting of molybdenum and chromium and 17 to 22 percent of an element selected from the group consisting of boron, silicon and mixtures thereof.

6. An alloy of claim 1 which is at least 85 percent amorphous, said alloy being characterized by the presence therein of discrete particles of its constituents, said particles having an average size ranging from about 0.1 µm to 0.3 µm and an average interparticle spacing of about 1 ^pm to 10 µm.

7. An alloy of claim 6, in which said discrete particles occupy and an average volume fraction of 0.005 to 0.01.

8. The method of enhancing the magnetic properties of the alloy recited in claim 1, comprising the step of annealing said alloy at a temperature and for a time sufficient to induce precipitation of discrete particles in said amorphous metal matrix.

9. A method as recited in claim 8, wherein the discrete particles consist essentially of a mixture of particles a portion of which mixture contains particles having a body-centered cubic structure, said particles being composed essentially of iron, up to 22 atom percent of said iron being adapted to be replaced by at least one of nickel, cobalt, chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium, havnium, silicon, and carbon.

10. A method as recited in claim 8, wherein the discrete particles consist essentially of a mixture of particles a portion of which mixture contains particles having a crystalline Fe₃B structure, said particles of said portion being composed of iron and boron, up to 14 atom percent of said iron being adapted to be replaced by at least one of nickel, cobalt, chromium, molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium, and hafnium, and up to 2 atom percent of said boron being adapted to be replaced by carbon.