Fe-based metallic glass for structural and functional use

Abstract

A bulk amorphous alloy includes the approximate composition Fe(100-a-b-c-d-e-f)YaMbTcAldSneBf wherein: M comprises at least one of the group consisting of: Zr, Hf, Pb, Ti, Nb, Mo and W; T comprises at least one of the group consisting of Co, Ni and Cr; a is an atomic percentage, and a<5; b is an atomic percentage, and 2≦b≦25; c is an atomic percentage, and 1≦c≦16; d is an atomic percentage, and d<5; e is an atomic percentage, and e<5; and f is an atomic percentage, and 11≦f≦22.

Description

FIELD OF THE INVENTION

[0002] The present invention relates to Fe-based bulk metallic glass compositions, and more particularly to Fe-based bulk metallic glass compositions containing additives such as Y, Al, Cr and Sn, and which are characterized by enhanced glass-forming ability, high material strength, and low material cost.

BACKGROUND OF THE INVENTION

[0003] Since the first Fe-based amorphous alloy system was synthesized in 1967, Fe-based amorphous metals have been successfully utilized in many application fields such as utility transformer, industrial transformer, power supplies, advanced power devices, magnetic sensors, electronic article surveillance and automotive magnetics. Nevertheless, all these amorphous alloys are inevitably produced by quenching at a cooling rate in the order of 106 K/s, thereby films with a maximum thickness of <100 &mgr;m can be fabricated. This largely restrains the commercial applications of Fe-based amorphous alloy. Enhancing glass-forming ability (GFA) of Fe-based alloys is thus under relentless pressure.

[0004] Perhaps the best conventional composition reported for bulk glass formation in Fe-base alloys is Fe61Zr10Co7Mo5W2B15. It was claimed that a glassy rod with diameters up to 6 mm could be produced by injecting the molten alloy into a copper mold. However, this result apparently cannot be duplicated by a conventional drop-casting technique in which the molten liquid was gravity-fed into a copper mold with a low vacuum capability. In FIG. 1 is the cross section microstructure of drop-casting 5 mm of Fe61Zr10Co7Mo5W2B15. As can be seen, no amorphous phase was formed. Hence, it is necessary to improve the GFA of Fe-based alloys in order enhance the ability thereof to form bulk glassy specimens under conventional industrial conditions, for example, commercial-grade raw materials, low vacuum furnace, conventional casting methods, etc. Thus, the alloys could be more viable for engineering applications.

[0005] Moreover, high purity elements like Zr, Co and W used in this alloy are costly, which results in a high material and production cost, making such alloys less attractive for commercialization. Therefore, less costly metals are needed to supersede those elements as much as possible, while improving glass forming ability and strength.

OBJECTS OF THE INVENTION

[0006] Accordingly, objects of the present invention include the provision of Fe-based compositions that have high glass-forming ability (GFA), that are made with inexpensive materials, can be formed into articles having cross-sections of at least 5 mm, high strength, and desirable magnetic properties. Further and other objects of the present invention will become apparent from the description contained herein.

SUMMARY OF THE INVENTION

[0007] In accordance with one aspect of the present invention, the foregoing and other objects are achieved by a bulk amorphous alloy that includes the approximate composition Fe(100-a-b-c-d-e-f)YaMbTcAldSneBf wherein: M comprises at least one of the group consisting of: Zr, Hf, Pb, Ti, Nb, Mo and W; T comprises at least one of the group consisting of Co, Ni and Cr; a is an atomic percentage, and a<5; b is an atomic percentage, and 2≦b≦25; c is an atomic percentage, and 1≦c≦16; d is an atomic percentage, and d<5; e is an atomic percentage, and e<5; and f is an atomic percentage, and 11≦f≦22.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a photomicrograph showing the morphology of a transverse cross-section of a base alloy of the formula Fe61Zr10Mo7Co5W2B15 drop-cast into a 5 mm copper mold.

[0009] FIG. 2 is a graph comparing atomic diameters of candidate constituent elements for bulk Fe-based metallic glass compositions.

[0010] FIG. 3a is photomicrograph showing the morphology of a transverse cross-section of a 5 mm, drop-cast, Y-doped base alloy of the formula Fe61YxZr10-xMo7Co5W2B15 where Y=1.9%, in accordance with the present invention.

[0011] FIG. 3b is photomicrograph showing the morphology of a transverse cross-section of a 5 mm, drop-cast, Y-doped base alloy of the formula Fe61YxZr10-xMo7Co5W2B15 where Y=3.0%, in accordance with the present invention.

[0012] FIG. 4a is photomicrograph showing the morphology of the edge of a transverse cross-section of a 7 mm, Y-doped and Sn-doped, drop-cast alloy of the formula Fe61-xSnxY1.9Zr8.1Mo7Co5Cr2B15 where Sn=0.1%, in accordance with the present invention.

[0013] FIG. 4b is photomicrograph showing the morphology of the center of a transverse cross-section of a 7 mm, Y-doped and Sn-doped, drop-cast alloy of the formula Fe61-xSnxY1.9Zr8.1Mo7Co5Cr2B15 where Sn=0.1%, in accordance with the present invention.

[0014] FIG. 4c is photomicrograph showing the morphology of the edge of a transverse cross-section of a 7 mm, Y-doped and Sn-doped, drop-cast alloy of the formula Fe61-xSnxY1.9Zr8.1Mo7Co5Cr2B15 where Sn=0.8%, in accordance with the present invention.

[0015] FIG. 4d is photomicrograph showing the morphology of the center of a transverse cross-section of a 7 mm, Y-doped and Sn-doped, drop-cast alloy of the formula Fe61-xSnxY1.9Zr8.1Mo7Co5Cr2B15 where Sn=0.8%, in accordance with the present invention.

[0016] FIG. 4e is photomicrograph showing the morphology of the edge of a transverse cross-section of a 7 mm, Y-doped and Sn-doped, drop-cast alloy of the formula Fe61-xSnxY1.9Zr8.1Mo7Co5Cr2B15 where Sn=1.15%, in accordance with the present invention.

[0017] FIG. 4f is photomicrograph showing the morphology of the center of a transverse cross-section of a 7 mm, Y-doped and Sn-doped, drop-cast alloy of the formula Fe61-xSnxY1.9Zr8.1Mo7Co5Cr2B15 where Sn=1.15%, in accordance with the present invention.

[0018] FIG. 4g is photomicrograph showing the morphology of the edge of a transverse cross-section of a 7 mm, Y-doped and Sn-doped, drop-cast alloy of the formula Fe61-xSnxY1.9Zr8.1Mo7Co5Cr2B15 where Sn=1.5%, in accordance with the present invention.

[0019] FIG. 4h is photomicrograph showing the morphology of the center of a transverse cross-section of a 7 mm, Y-doped and Sn-doped, drop-cast alloy of the formula Fe61-xSnxY1.9Zr8.1Mo7Co5Cr2B15 where Sn=1.5%, in accordance with the present invention.

[0020] FIG. 5a is photomicrograph showing the morphology of a transverse cross-section of a 5 mm, Al-doped, drop-cast alloy of the formula Fe61Y1.9Zr8.1Mo7Co6B15Al1 in accordance with the present invention.

[0021] FIG. 5b is photomicrograph showing the morphology of a transverse cross-section of a 5 mm, Al-doped, drop-cast alloy of the formula Fe60Y1.9Zr8.1Mo7Co7B15Al1 in accordance with the present invention.

[0022] FIG. 5c is photomicrograph showing the morphology of a transverse cross-section of a 5 mm, Al-doped, drop-cast alloy of the formula Fe61Y1.9Zr7.1Mo7Co6B15Al1 in accordance with the present invention.

[0023] FIG. 6a is photomicrograph showing the morphology of a transverse cross-section of a 7 mm, Cr-doped, drop-cast alloy of the formula Fe61Y1.9Zr8.1Mo7CrxCo7-xB15 where Cr=1%, in accordance with the present invention.

[0024] FIG. 6b is photomicrograph showing the morphology of a transverse cross-section of a 7 mm, Cr-doped, drop-cast alloy of the formula Fe61Y1.9Zr8.1Mo7CrxCo7-xB15 where Cr=2%, in accordance with the present invention.

[0025] FIG. 6c is photomicrograph showing the morphology of a transverse cross-section of a 7 mm, Cr-doped, drop-cast alloy of the formula Fe61Y1.9Zr8.1Mo7CrxCo7-xB15 where Cr=3%, in accordance with the present invention.

[0026] FIG. 6d is photomicrograph showing the morphology of a transverse cross-section of a 7 mm, Cr-doped, drop-cast alloy of the formula Fe61Y1.9Zr8.1Mo7CrxCo7-xB15 where Cr=4%, in accordance with the present invention.

[0027] FIG. 7a is photomicrograph showing the morphology of a transverse cross-section of a 5 mm, Al-doped, drop-cast alloy of the formula (Fe61Y1.9Zr8.1Mo7Co6Al1)[(100-x)/85]Bx where B=16% in accordance with the present invention.

[0028] FIG. 7b is photomicrograph showing the morphology of a transverse cross-section of a 5 mm, Al-doped, drop-cast alloy of the formula (Fe61Y1.9Zr8.1Mo7Co6Al1)[(100-x)/85]Bx where B=18% in accordance with the present invention.

[0029] FIG. 8 is photograph showing the outer morphology of 3 mm and 5 mm, Al-doped, drop-cast alloy cylinders of the formula Fe61Y1.9Zr8.1Mo7Co6B15Al1 in accordance with the present invention.

[0030] FIG. 9 is photomicrograph showing the morphology in the center of a transverse cross-section of a 5 mm, drop-cast alloy of the formula Fe61Y1.9Zr8.1Mo7Co7B15 in accordance with the present invention.

[0031] FIG. 10 is a graph showing an X-ray diffraction (XRD) pattern of a 5 mm, drop-cast alloy of the formula Fe61Y1.9Zr8.1Mo7Co7B15 in accordance with the present invention.

[0032] FIG. 11 is a graph showing a differential scanning calorimetry (DSC) trace of a 5 mm, drop-cast alloy of the formula Fe61Y1.9Zr8.1Mo7Co7B15 in accordance with the present invention.

[0033] For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above-described drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0034] For purposes of this invention, a fully metallic glass (amorphous alloy) product is defined as a material that comprises at least 70 volume % amorphous phase. The amorphous nature of the metallic glasses can be verified by a number of well-known techniques. The volume fraction of amorphous material in a sample can be estimated by analysis of photomicrographs. Frequently, materials produced in practice of the present invention comprise a single amorphous phase. The approximate chemical formula of the compositions of the present invention can be expressed as follows:

Fe(100-a-b-c-d-e-f)YaMbTcAldSneBf

[0035] In the above formula:

[0036] M is at least one of: Zr, Hf, Pb, Ti, Nb, Mo and W

[0037] T is at least one of: Co, Ni and Cr

[0038] a, b, c, d, e and f are atomic percentages, wherein:

[0039] a<5

[0040] 2≦b≦25

[0041] 1≦c≦16

[0042] d<5

[0043] e<5

[0044] 11≦f≦22

[0045] It is preferable in the present invention that M is represented by:

ZrgMoh

[0046] wherein:

[0047] g+h=b

[0048] g<9

[0049] h<10

[0050] 4≦b≦17

[0051] It is also preferable in the present invention that T is represented by:

CoiCrj

[0052] wherein:

[0053] h+j=c

[0054] h<8

[0055] j<6

[0056] 4≦c≦10

[0057] More preferably, a very good glass-forming alloy within the compositional ranges described above has the approximate formula:

Fe(100-a-g-h-i-j-d-e-f)YaZrgMohCoiCrjAldSneBf

[0058] In the above formula:

[0059] a, b, c, d, e, f and g are atomic percentages, wherein:

[0060] 1≦a≦3

[0061] 2≦g≦8

[0062] 4≦h≦9

[0063] 4≦i≦8

[0064] j<3

[0065] (d+e)<2

[0066] 14≦f≦18

[0067] The above formulae are described as approximate because there can be small variations in constituent amounts—usually less than 1 atomic %.

[0068] One of the predominant factors influencing GFA can be found in the various atomic radii of constituent elements. FIG. 2 shows comparative atomic diameters of candidate constituent elements for bulk Fe-based metallic glass compositions. A large difference in atomic size for the constituent elements can result in a higher degree of dense random packed structure, which favors glass formation from both thermodynamic and kinetic perspectives. Several elements were therefore selected for optimizing GFA in Fe alloys, which are categorized below in terms of atomic sizes:

[0069] 1) Huge atoms (atomic volumes are twice that of Fe atom), for example, Zr, Sn, Y and rare earths such as La, Nd and Ce

[0070] 2) Large atoms, for example, Mo, W, Nb, Ta, Al and Ti

[0071] 3) Intermediate atoms, for example, Co, Cr and Ni

[0072] 4) Small atoms, for example, B, P, Si and C

[0073] It should be noted that glass formation is a complex phenomenon that is affected by various interactions among most or all of the constituent elements. Effect of atomic size is a general, empirical consideration for searching new glass forming compositions. Experimentation has produced the following results:

[0074] Effects Of Huge Atoms

[0075] Table 1 lists alloy compositions prepared for the present invention. The addition of rare earth elements, for example, Nd, La and Ce, in Fe-based alloys is usually expected to generate uni-axial magnetic anisotropy and increase cohesive force. The resulting alloy has desirable magnetic properties. Normally, effective compositional range of rare earth elements is expected to be from 5 to 15 atomic %. However, in accordance with the present invention, the addition of small amount of element Y, i.e. below 5%, can enhance GFA remarkably. Preferably, the doped Y content is no more than 3%. Higher Y content can be deleterious to the GFA of the alloy. FIGS. 3a, 3b are micrographs of transverse cross section of the samples drop cast with 5 mm diameter copper mould and doped with various Y contents in Fe61Zr10-aYaCo7Mo5W2B15 system, clearly showing the Y effect on glass forming ability in this alloy system. Without any Y addition (a=0), drop-cast base alloy displayed a fully crystalline structure as shown in FIG. 1. When 1.9% Y supersedes part of Zr in this alloy (alloy 1 in Table 1), a large area of featureless amorphous phase was observed as depicted in FIG. 3(a), indicating that the GFA of this alloy has been greatly improved in comparison with the base alloy shown in FIG. 1. If increasing Y to 3% (alloy 2), most of crystalline phases was formed for this bulk-casting sample as seen in FIG. 3b. It is concluded that the Y content should not generally exceed 5% for glass formation in Fe based alloys as far as the GFA is concerned. Furthermore, replacing high purity metal Zr with Y in the base alloy Fe61Zr10Co7Mo5W2B15 is a promising way to reduce the production cost at no expense of glass forming ability.

[0076] Other huge elements, including Zr, Hf, Pb, and Sn, are also very effective in promoting glass formation in Fe based alloys. In the present invention, it was found that Zr and Hf are interchangeable and their total amount should be in the range from 4 to 14 at. %. It was also found that Sn had a very special influence on glass forming ability for bulk glass formation in Fe based alloys. As an example, FIGS. 4a-4h show the transverse cross section morphologies of drop-cast 7 mm rods containing various levels of Sn, apparently demonstrating Sn effect on GFA in the Fe61-eSneY1.9Zr8.1Co5Cr2Mo7B15 system. When only 0.1 at. % Sn was doped, the alloy (alloy 66) exhibited a fine crystalline structure with some dispersions of primary phase in the area nearby circumference (edge) and a coarse crystalline structure in the central part of the rod (center), as shown in FIGS. 4b and 4b, respectively. As Sn was increased to 0.85 at. % in this system (alloy 77), the edge area displayed a partially amorphous structure, as shown in FIG. 4c. However in the central part of the sample, although there are similar primary phases present, the remaining matrix is still crystalline structure with visible small grains, as shown in FIG. 4d. When Sn level was increased further to 1.15 at. % (alloy 78), the whole sample showed a partially amorphous structure, indicating the further enhancement of the glass forming ability, as shown in FIGS. 4e, 4f. Additionally, FIGS. 4e, 4f exhibit typical composite structures with primary phases dispersed in an amorphous matrix, which usually leads to increased strength and ductility. Nevertheless, high content of Sn (≧1.4 at. %) in this system is detrimental to glass forming ability, as evidenced in FIGS. 4g, 4h (alloys 73 and 72). 1 TABLE I Alloy Amorphous Casting size No. Composition volume fraction mm 0 Fe61Zr10Mo5W2Co7B15 Fully crystalline 5 1 Fe61Y1.9Zr8.1Mo5W2Co7B15 Partially amorphous 5 2 Fe61Y3Zr7Mo5W2Co7B15 Fully crystalline 5 3 Fe61Y4Zr6Mo5W2Co7B15 Fully crystalline 5 4 Fe61Y1.9Zr8.1Mo5W2Ni7B15 Fully crystalline 5 5 Fe61Y1.9Zr8.1Mo7Co7B15 Fully amorphous 5 6 Fe61Y1.9Zr8.1Mo5W2Co7Si5B10 Fully crystalline 5 7 Fe61Y1.5Zr8.5Mo5W2Co7B15 Fully amorphous 5 8 Fe61Y2.5Zr7.5Mo5W2Co7B15 Fully amorphous 5 9 Fe61Y1.9Zr8.1Mo7Co7Si1B14 Fully crystalline 5 10 Fe61Y1.9Zr8.1Mo7Co7Si3B13 Fully crystalline 5 11 Fe61Y1.9Zr8.1Mo7Co7Si3B12 Fully crystalline 5 12 Fe61Y1.9Zr8.1Mo7Co5Ni2B15 Fully amorphous 5 13 Fe61Y1.9Zr8.1Mo7Co3Ni4B15 Partially amorphous 5 14 Fe61Y1.9Zr6.1Mo7Co7Sn2B15 Partially amorphous 5 15 Fe61Y1.9Zr4.1Mo7Co7Sn4B15 Partially amorphous 5 16 Fe61Y1.9Zr2.1Mo7Co7Sn6B15 Fully crystalline 5 17 Fe61Y1.9Zr6.1Ti2Mo7Co7B15 Partially amorphous 5 18 Fe61Y1.9Zr4.1Ti4Mo7Co7B15 Partially amorphous 5 19 Fe60Y1.9Zr8.1Mo7Co7B15Al1 Partially amorphous 5 20 Fe61Y1.9Zr7.1Mo7Co7B15Al1 Partially amorphous 5 21 Fe61Y1.9Zr8.1Mo7Co6B15Al1 Fully amorphous 5 22 (Fe61Y1.9Zr8.1Mo7Co6Al1)0.84/0.85B16 Partially amorphous 5 23 (Fe61Y1.9Zr8.1Mo7Co6Al1)0.83/0.85B17 Partially amorphous 5 24 (Fe61Y1.9Zr8.1Mo7Co6Al1)0.82/0.85B18 Partially amorphous 5 25 (Fe61Y1.9Zr8.1Mo7Co6Al1)0.855/0.85B14.5 Fully amorphous 5 26 (Fe61Y1.9Zr8.1Mo7Co6Al1)0.845/0.85B15.5 Fully amorphous 5 27 Fe61Y1.9Zr8.1Mo5Cr2Co7B15 Partially amorphous 5 28 Fe61Y1.9Zr6.1Mo7Cr2Co7B15 Fully amorphous 5 29 Fe61Zr10Mo5W2Co3.5Ni3.5B15 Fully crystalline 5 30 Fe60.8Zr9Mo5W2Co7B15Si0.2Pb1 Partially amorphous 5 31 Fe61Zr10Mo5W2Co7B10C5 Fully crystalline 5 32 Fe67Y1.9Zr6.1Mo5W2Co7B11 Fully crystalline 5 33 Fe66Y1.9Zr7.1Mo5W2Co7B11 Partially amorphous 5 34 Fe65Y1.9Zr8.1Mo5W2Co7B11 Partially amorphous 5 35 Fe65Y1.9Zr6.1Mo5W2Co7B13 Partially amorphous 5 36 Fe64Y1.9Zr7.1Mo5W2Co7B13 Partially amorphous 5 37 Fe65Y1.9Zr6.1Mo5W2Co7B13 Fully crystalline 5 38 Fe61Zr4.1Cr4Y1.9Co7Mo7B15 Partially amorphous 5 39 Fe61.1Cr8Y1.9Co7Mo7B15 Fully crystalline 5 40 Fe55Y1.9Zr14.1Co6Al1Mo7B15 Fully crystalline 5 41 Fe63Zr8Co6Al1Mo7B15 Partially amorphous 5 42 Fe59Y4Zr8Co6Al1Mo7B15 Fully amorphous 5 43 Fe57Y6Zr8Co6Al1Mo7B15 Partially amorphous 5 44 Fe58Y1.9Zr11.1Co6Al1Mo7B15 Fully crystalline 5 45 Fe53Y10Zr8Co6Al1Mo7B15 Partially amorphous 5 46 Fe61Zr8.1Y1.9Co7Cr7B15 Fully crystalline 5 47 Fe61Zr8La2Co7Mo7B15 Partially amorphous 5 48 Fe61Zr6.1Nb2Y1.9Co7Mo7B15 Partially amorphous 5 49 Fe61Zr8.1Y1.9Co5Cr2Mo7B15 Fully amorphous 5 Almost fully amorphous 7 50 Fe55(Y1.9Zr8.1Co6Al1Mo7B15)45/39 Fully crystalline 5 51 Fe61Zr8.1Y1.9Co3Cr4Mo7B15 Fully crystalline 7 52 Fe71.5Zr7Y6.5B15 Fully crystalline 7 53 Fe61Zr8.1Y1.9Co4Cr3Mo7B15 Partially amorphous 7 54 Fe61Zr8.1Y1.9Co6Cr1Mo7B15 Partially amorphous 7 55 Fe63Zr8.1Y1.9Co6Al1Mo7B15 Partially amorphous 5 56 Fe61Zr8.1Y1.9Co4.5Cr2.5Mo7B15 Partially amorphous 7 57 Fe61Zr6.1Y1.9Co5Cr2Mo7B15 Partially amorphous 7 58 Fe61Zr8.1Y1.9Co4Al1Cr2Mo7B15 Partially amorphous 5 59 Fe60Zr8.1Y1.9Co4Al2Cr2Mo7B15 Partially amorphous 5 60 Fe59Zr8.1Y1.9Co3Al4Cr2Mo7B15 Partially amorphous 5 61 Fe60Zr8.1Y1.9Co4Al2Cr2Mo7B15 Partially amorphous 5 62 Fe61Zr8.1Y1.9Co5Al1Cr1Mo7B15 Fully amorphous 5 63 Fe60Zr8.1Y1.9Co5Al1Cr2Mo7B15 Fully amorphous 5 64 Fe59Zr8.1Y1.9Co5Cr2Mo7B15 Partially amorphous 7 65 Fe59Zr8.1Y1.9Co7Cr2Mo7B15 Partially amorphous 7 66 Fe60.9Zr8.1Y1.9Co5Cr2Mo7B15Sn0.1 Partially amorphous 7 67 Fe60.5Zr8.1Y1.9Co5Cr2Mo7B15Sn0.5 Partially amorphous 7 68 Fe60Zr8.1Y1.9Co5Cr2Mo7B15Sn1 Fully amorphous 7 69 Fe59Zr8.1Y1.9Co5Cr2Mo7B15La2 Partially amorphous 7 70 Fe60.8Zr8.1Y1.9Co5Cr2Mo7B15Sn0.3 Partially amorphous 7 71 Fe60.8Zr8.1Y1.9Co5Cr2Mo7B15Pb0.2 Partially amorphous 7 72 Fe59Zr8.1Y1.9Co5Cr2Mo7B15Sn2 Fully crystalline 7 73 Fe59.5Zr8.1Y1.9Co5Cr2Mo7B15Sn1.5 Fully crystalline 7 74 Fe56Zr8.1Y1.9Co5Cr2Mo7B15Sn5 Partially amorphous 7 75 Fe60.5Ar8.1Y1.9Co5Cr2Mo7B15Pb0.5 Almost fully amorphous 7 76 Fe60Zr8.1Y1.9Co5Cr2Mo7B15Pb1 Fully crystalline 7 77 Fe60.15Zr8.1Y1.9Co5Cr2Mo7B15Sn0.85 Partially amorphous 7 78 Fe59.85Zr8.1Y1.9Co5Cr2Mo7B15Sn1.15 Fully amorphous 7 79 Fe61Nb9.1Y1.9Co5Cr2Mo7B15 Partially amorphous 5 80 (Fe59.85Zr8.1Y1.9Co5Cr2Mo7SN1.15)88/85B12 Fully crystalline 7 81 (Fe59.85Zr8.1Y1.9Co5Cr2Mo7Sn1.15)85.5/85B14.5 Fully amorphous 7 82 (Fe59.85Zr8.1Y1.9Co5Cr2Mo7Sn1.15)86/85B14 Partially amorphous 7 83 (Fe59.85Zr8.1Y1.9Co5Cr2Mo7Sn1.15)87/85B13 Fully crystalline 7 84 (Fe59.85Zr8.1Y1.9Co5Cr2Mo7Sn1.15)84/85B16 Partially amorphous 7 85 Fe61Zr8.1Y1.9Co5Cr2Ni7B15 Fully crystalline 7 86 Fe61Zr6.1Hf2Y1.9Co5Cr2Mo7B15 Almost fully amorphous 7 87 Fe60Zr8.1Y1.9Co7Mo7B15Sn1 Partially amorphous 7 88 Fe60Zr8.1Y1.9Co6Al1Mo7B15Sn1 Fully crystalline 7 89 Fe57Zr7Y2Co7Mo8B19 Partially amorphous 7 90 Fe34Zr8.1Y1.9Co34Mo7B15 Fully crystalline 7 91 Fe60.25Zr7.7Y1.9Co5Cr2Mo7B15Sn1.15 Almost fully amorphous 7 92 Fe58.85Zr8.1Y1.9Co5Cr3Mo7B15Sn1.15 Fully amorphous 7 93 Fe59Zr8.1Y1.9Co5Mo7Cr2Ga2B15 Partially amorphous 7 94 Fe31Ni30Zr8Y2Co7Mo7B15 Fully crystalline 7 95 Fe58.25Zr7.6Y2Co5Mo7Cr4B15Sn1.15 Almost fully amorphous 7 96 Fe53.25Zr7.6Y2Co7Mo7Cr7B15Sn1.15 Partially amorphous 7 97 Fe61.85Zr8Co5Mo7Cr2B15Sn1.15 Partially amorphous 7 98 Fe60Zr8.1Y1.9Co5Mo7Cr3B15 Partially amorphous 7 99 Fe60Zr8Co5Mo7Cr2B15Sn3 Fully crystalline 7 100 Fe57Zr8Y2Co5Mo7Cr2B15Si2 Fully crystalline 7 101 Fe59Zr8.1Y1.9Co5Cu2Mo7B15Cr2 Partially amorphous 7 102 Fe59.5Zr8.1Y1.9Co5Mo7Cr3B15Sn0.5 Partially amorphous 7 Note: Fully amorphous: the volume fraction of amorphous phase is above 70%. Almost fully amorphous: the volume fraction of amorphous phase is in between 60 and 70% (for 7 mm casting size).

[0077] Effects Of Large Atoms

[0078] The addition of large elements Mo, W and Al are also beneficial to GFA in Fe based alloys. Al and Mo are preferred elements for the industry because of their relatively low cost and material density. It is important to point out that Al must supersede the correct element in the composition; otherwise addition of Al can be detrimental to the GFA. As an example shown in FIG. 5a, a fully amorphous structure was seen when 1% Al replaced 1% Co in the alloy Fe61Y1.9Zr8.1Mo7Co7B15 (alloy 21). FIGS. 5b, 5c show that only partially amorphous structure were obtained in samples in which 1% Al substituted for 1% Fe (alloy 19) and 1% Zr in this alloy (alloy 20), respectively.

[0079] In the present invention, it is preferable that the element M is represented by (ZrgMoh) with g being less than 9, h being less than 10 and g+h being in the range of from 4 to 17, Y ranges from 1 to 3, Sn is from 0 to 2 and Al is in the range from 0 to 2. Compared with the base alloy Fe61Zr10Co7Mo5W2B15, the production cost is reduced for the new alloy with low content of pure Zr and without element W.

[0080] Effects Of Intermediate Atoms

[0081] One or a plurality of elements T selected from Co, Ni and Cr can be further added into the composition presented to increase GFA. From a production point of view, Co content should be as low as possible because of the high material cost thereof. In the present invention, the element T is preferably represented by (CoiCrj) with i being less than 8, j being less than 6 and i+j being in the range of from 4 to 10. FIGS. 6a-6d demonstrate the effect of element Cr on GFA in Fe61Zr8.1Y1.9Co7-jCrjMo7B15 system by illustrating the morphology of transverse cross section of drop casting 7 mm cylindrical samples (alloys 48-51). As is clear from FIG. 6b, the optimum dose of Cr addition is about 2 at. % in this system (alloy 49). High Cr level decreases GFA, as shown in FIG. 6(d) for the sample Cr=4% (alloy 51) in which amorphous structure was totally absent. Substitution of pure metal Co with Cr in the new alloys results in a further decrease in the production cost compared with the base alloy Fe61Zr10Co7Mo5W2B15.

[0082] Effects Of Small Atoms

[0083] Element B is effective for enhancing the GFA in this invention. Its content ranges from 11 to 22 atomic %. A composition with lower than 11% or higher than 22% B does not generally form an amorphous phase using the copper mould drop-casting technique. More preferably, it is in the range of from 13 to 16 atomic %. An addition of less than 13 or above 16 atomic percentage is generally less effective in enhancing the glass forming ability of the resultant samples (see Table 1). FIGS. 7a, 7b show the exemplary microstructure change for 5 mm drop-casting cylindrical samples with different levels of B doped in (Fe61Y1.9Zr8.1Mo7Co6Al1)[(100-f)/85]Bf alloys, illustrating B effect on GFA in these alloys. Featureless image except for some black dots was obtained in FIG. 5a for the specimen that included 15% B (alloy 21). It was confirmed that the black dots are due to casting-induced pores. When B was increased to 16% (alloy 22), the fraction of amorphous structure was much reduced and crystalline phases started to grow in the central part of the specimen, as shown in FIG. 7a. Further increasing B level to 18% (alloy 24), only a small portion of amorphous structure close to sample surface was observed, as shown in FIG. 7b. These results suggest that B level should be strictly controlled for bulk glass formation in Fe based alloys.

[0084] Production of Fe based bulk amorphous alloys in the present invention was as follows: Firstly, a Fe-33%Y master alloy was prepared and cast into sheets. Subsequently, based on the desired compositional ranges described hereinabove, mixtures of alloying metals and the master alloy were arc-melted in an argon atmosphere to form an alloy of the desired composition, which was allowed to solidify into a homogeneous alloy. The alloy was then re-arc-melted over a copper mould in an argon atmosphere. The molten liquid was drop cast into the mould via gravity and the electromagnetic arc force. The copper moulds were 3-8 mm in diameter. The resultant cast samples were generally 50-70 mm in length. The morphologies of the samples were analyzed by microscopy, X-ray diffraction (XRD), and differential scanning calorimetry (DSC).

[0085] Table 1 summarizes the alloy compositions which were drop-cast into a copper mold with diameters of 3 to 8 mm. As can be seen, there are various compositions that can be drop cast into the shape of a 5 mm rod with more than 70% by volume amorphous phase. Some of the very good glass forming compositions, for example, Fe61Y1.9Zr8.1Mo7Co7B15 (alloy 5), Fe61Y1.9Zr8.1Mo7Co6B15Al1 (alloy 21), and Fe61Y1.9Zr8.1Mo7Co5Cr2B15 (alloy 49), can form fully amorphous structure by drop casting technique to a 5 mm diameter. Particularly, for some of the best alloys, for example, Fe60Y1.9Zr8.1Mo7Co5Cr2B15Sn1 (alloy 68), Fe59.85Y1.9Zr8.1Mo7Co5Cr2B15Sn1.15 (alloy 78), and Fe58.85Zr8.1Y1.9Co5Cr3Mo7B15Sn1.15 (alloy 92), a 7 mm rod with mostly single amorphous structure with small fraction of primary phases can be obtained using the drop-casting technique. FIG. 8 shows the outer morphology and surface appearance of drop cast Fe61Y1.9Zr8.1Mo7Co6B15Al1 alloy (alloy 21) cylinders with diameters of 3 and 5 mm. These samples display a smooth surface and metallic luster. No contrast of a crystalline phase is seen over the outer surface. FIG. 9 shows a photomicrograph of the central part of the transverse cross section in the cast Fe61Y1.9Zr8.1Mo7Co7B15 rod (alloy 5) with a diameter of 5 mm. No contrast corresponding to a crystalline phase is seen, although casting-induced pores distinguished as dark spots are observed. The corresponding X-ray diffraction (XRD) pattern and differential scanning calorimetry (DSC) trace for this alloy are shown in FIGS. 10 and 11, respectively. No crystalline peak was observed in the XRD spectrum. Typical glass transition and crystallization transformations were seen in the DSC trace. All these confirm that the 5 mm as-cast cylinder sample has mostly single amorphous structure.

[0086] The Fe based bulk amorphous alloys of the present invention can also be prepared by many, well known, conventional techniques, for example, water quenching, suction casting, wage casting, and powder metallurgy routes such as warm consolidation processing, etc. It is expected that larger sizes of glassy alloy articles can be fabricated using techniques with higher cooling capacities, for example, high-pressure suction casting, high-pressure injection casting, high-pressure die casting, etc. Some special preparation techniques like flux melting are also contemplated to enhance GFA.

[0087] The hardness of the materials prepared as described hereinabove was measured by applying a load of 200 g using a conventional hardness tester. Bulk amorphous alloys of the present invention generally have extremely high hardness. Table 2 tabulates the hardness values for 5 mm glassy rods in three alloys Fe61Y1.9Zr8.1Mo7Co7B15 (alloy 5), Fe61Y1.9Zr8.1Mo7Co6B15Al1 (alloy 21), and Fe61Y1.9Zr8.1Mo7Co5Cr2B15 (alloy 49). As is clear from the data shown in Table 2, the bulk amorphous alloys within the range of the composition of the invention gave a Vickers harness value close to Hv 1200. High Vickers hardness values indicate extremely high strength of the material. 2 TABLE II Composition Hv Fe61Y1.9Zr8.1Mo7Co7B15 1183 ± 31 Fe61Y1.9Zr8.1Mo7Co6B15Al1 1181 ± 30 Fe61Y1.9Zr8.1Mo7Co5Cr2B15 1221 ± 21

[0088] Uniqueness of the present invention can be attributed to at least the following:

[0089] 1) The present invention provides a new Fe based alloy with much higher glass forming ability than that of existing Fe based alloys reported in the literature. To date, the best composition for glass formation in Fe based is Fe61Zr10Mo5W2Co7B15 alloy. A 6 mm glassy cylinder could be allegedly obtained by means of injecting the molten liquid into a copper mold under laboratory conditions. The cooling rate of this technique is about the order of 103 to 104 K/s. However, no amorphous structure was obtained by drop casting technique at even smaller size which corresponds to a lower cooling rate of 102 to 103 K/s with a low vacuum capability of ˜103 torr. Conversely, in the present invention, a new alloy having high glass forming ability and being able to form at least 5 mm amorphous rod using the latter method.

[0090] 2) For the first time, element Y was doped into the Fe based alloy for bulk glass formation. It was found that the addition of small amount of Y can dramatically promote bulk glass formation in Fe based alloys. Compared with the base alloy Fe61Zr10Co7Mo5W2B15, using Y to replace high purity Zr can also reduce the production cost at no expense of GFA, in accordance with the present invention.

[0091] 3) Element Sn was also found to be able to enhance glass forming ability dramatically in Fe based alloys. Particularly, an in-situ composite material, e.g a mixture of primary phase and amorphous matrix can be obtained, which usually leads to increased ductility of the material.

[0092] 4) Using Al, Mo, Cr and/or Ni to supersede pure metal W and part of Co in the base alloy increases the GFA, and also decrease the production cost, in accordance with the present invention.

[0093] 5) Fe and Co affect saturated magnetic flux density and an excellent magnetic properties.

[0094] 6) The alloy of the present invention, exhibiting the unique combination of high GFA, the ability of being produced in bulk form with fully amorphous structure, very high strength and good magnetic properties is expected to have great potential for many structural and functional applications. Articles that can be formed of the compositions of the present invention include, but are not limited to, for example: machinery and machine components such as gears, shafts, levers, cams, etc.; structural articles and components such as frames, braces, plates, rods, bars, etc.; precision optical articles and components; dies; hand and power tools and components; medical instruments and components; cutting tools, instruments and components; springs and other resilient articles and components; molds, equipment and components for high-resolution replication; armor-piercing projectiles and other weapons components; and recreational articles such as fishing rods, tennis rackets, golf club components, and bicycle components.

[0095] 7) High GFA is generally related to high thermal stability. Bulk amorphous alloys have the ability to be manufactured near net shape. Therefore, the alloys of the present invention can be used in the fabrication of articles having fine surface irregularites such as gears, a milling heads, golf club shafts and a golf club heads.

[0096] 8) Fe based bulk metallic glasses generally display very good magnetic properties. Sometimes the annealing process of bulk amorphous materials can result in even better magnetic characteristics. Therefore, the alloys of the present invention can be used as: core materials in energy-efficient electrical power devices, high efficiency electrical transformers, air conditioners, and the like; electronic survillance equipment; magnetic sensors; automotive magnetic equipment; efficent electrodes; and writing appliance materials.

[0097] While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications can be prepared therein without departing from the scope of the inventions defined by the appended claims.

Claims

1. A bulk amorphous alloy composition comprising the approximate composition Fe(100-a-b-c-d-e-f)YaMbTcAldSneBf wherein:

a. M comprises at least one of the group consisting of: Zr, Hf, Pb, Ti, Nb, Mo and W;

b. T comprises at least one of the group consisting of Co, Ni and Cr;

c. a is an atomic percentage, and a<5;

d. b is an atomic percentage, and 2≦b≦25;

e. c is an atomic percentage, and 1≦c≦16;

f. d is an atomic percentage, and d<5;

g. e is an atomic percentage, and e<5; and

h. f is an atomic percentage, and 11≦f≦22.

2. A bulk amorphous alloy composition in accordance with claim 1 wherein M further comprises ZrgMoh wherein:

a. g+h=b

b. g<9

c. h<10

d. 4≦b≦17

3. A bulk amorphous alloy composition in accordance with claim 1 wherein T further comprises CoiCrj wherein:

a. i+j=c

b. i<8

b. j<6

c. 4≦c≦10

4. A bulk amorphous alloy composition in accordance with claim 1 further comprising the approximate composition Fe(100-a-g-h-i-j-d-e-f)YaZrgMohCoiCrjAldSneBf wherein:

a. 1≦a≦3

b. 2≦g≦8

c. 4≦h≦9

d. 4≦i≦8

e. j<3

f. (d+e)<2

g. 14≦f≦18

5. A bulk amorphous alloy composition in accordance with claim 1 further comprising the approximate composition Fe61Y1.9Zr8.1Mo7Co7B15.

6. A bulk amorphous alloy composition in accordance with claim 1 further comprising the approximate composition Fe61Y1.9Zr8.1Mo7Co6B15Al1.

7. A bulk amorphous alloy composition in accordance with claim 1 further comprising the approximate composition Fe61Y1.9Zr8.1Mo7Co5Cr2B15.

8. A bulk amorphous alloy composition in accordance with claim 1 further comprising the approximate composition Fe59.85Sn1.15Y1.9Zr8.1Mo7Co5Cr2B15.

9. A bulk amorphous alloy composition in accordance with claim 1 further comprising the approximate composition Fe60Sn1Y1.9Zr8.1Mo7Co5Cr2B15.

10. A bulk amorphous alloy composition in accordance with claim 1 further comprising the approximate composition Fe58.85Sn1.15Y1.9Zr8.1Mo7Co5Cr3B15.

11. A bulk amorphous alloy composition in accordance with any one of claims 1-10, inclusive, wherein said bulk amorphous alloy composition is formed into an article.