US20160090644A1

US20160090644A1 - Bulk nickel-cobalt-based glasses bearing chromium, tantalum, phosphorus and boron

Info

Publication number: US20160090644A1
Application number: US14/501,779
Authority: US
Inventors: Jong Hyun Na; Oscar Abarca; Chase Crewdson; Maximilien Launey; Marios D. Demetriou; William L. Johnson
Original assignee: Glassimetal Technology Inc
Current assignee: Glassimetal Technology Inc
Priority date: 2014-09-30
Filing date: 2014-09-30
Publication date: 2016-03-31
Also published as: US20170152587A9

Abstract

Ni—Co—Cr—Ta—P—B alloys and metallic glasses with controlled ranges are provided. The alloys demonstrate a combination of good glass forming ability, high toughness, and high stability of the supercooled liquid. The disclosed alloys are capable of forming metallic glass rods of diameters at least 3 mm and up to about 8 mm or greater. Certain alloys with good glass forming ability also have high notch toughness approaching 100 MPa m^1/2, and stability of the supercooled liquid approaching 60° C.

Description

TECHNICAL FIELD

The present disclosure relates to Ni—Co—Cr—Ta—P—B alloys capable of forming metallic glass with critical rod diameters of at least 3 mm and as large as 8 mm or larger.

BACKGROUND

Ni—Cr—Ta—P—B alloys with critical rod diameters of 3 mm or larger have been disclosed in U.S. patent application Ser. No. 14/081,622, entitled “Bulk Nickel-Phosphorus-Boron Glasses Bearing Chromium Tantalum”, filed on Nov. 15, 2013, the disclosure of which is incorporated herein by reference in its entirety. In this application, bulk glass forming ability is identified for Cr content ranging from 3 to 11 atomic percent, Ta content ranging from 1.75 to 4 atomic percent, P content ranging from 14 to 17.5 atomic percent, and B content ranging from 2.5 to 5 atomic percent. Bulk metallic glasses rods with critical rod diameters as large as 7 mm can be formed within those ranges.
Although the application states that Ni or Cr substitution by Co of up to 2 atomic percent may not impair the glass forming ability of the disclosed alloys, it does not address the potential of glass formation of Ni—Co—Cr—Ta—P—B alloys, where Co concentrations of up to 40 atomic percent are included.

BRIEF SUMMARY

The present disclosure is directed to Ni—Co—Cr—Ta—P—B alloys and metallic glasses comprising Ni—Co—Cr—Ta—P—B alloys, where Co is included in concentrations of up to 40 atomic percent. The alloys have critical rod diameters of at least 3 mm and up to 8 mm or larger. In some embodiments, the metallic glasses may also exhibit notch toughness values in excess of 90 MPa m^1/2.
In one embodiment, the disclosure provides an alloy or a metallic glass formed of an alloy represented by the following formula (subscripts denote atomic percent):
Ni_{(100-a-b-c-d-e)}Co_aCr_bTa_cP_aB_e Eq. (1)
where:
a ranges from 0.5 to 40
b ranges from 3 to 11
c ranges from 1.5 to 4
d ranges from 14 to 17.5
e ranges from 2 to 5.
In various aspects, the critical rod diameter of the alloys is at least 3 mm.
In another embodiment, c is determined by x+y·b, where x is between 1.5 and 2 and y is between 0.1 and 0.15.
In another embodiment, a ranges from 0.5 to 30, b ranges from 8 to 10.5, c ranges from 2.25 to 3.75, d ranges from 15.5 to 17, e ranges from 2.5 to 4. In various aspects, the critical rod diameter of the alloy is at least 5 mm.
In another embodiment, a ranges from 0.5 to 15, b ranges from 8.5 to 10, c ranges from 2.5 to 3.5, d ranges from 15.75 to 16.75, e ranges from 2.75 to 3.75. In various aspects, the critical rod diameter of the alloy is at least 6 mm.
In another embodiment, a ranges from 0.5 to 30, b ranges from 6 to 8, c ranges from 2 to 3.5, d ranges from 15.5 to 17, e ranges from 2.5 to 4. In various aspects, the critical rod diameter of the alloy is at least 5 mm.
In another embodiment, a ranges from 0.5 to 5, b ranges from 6.5 to 7.5, c ranges from 2.25 to 3.25, d ranges from 15.75 to 16.75, e ranges from 2.75 to 3.75. In various aspects, the critical rod diameter of the alloy is at least 6 mm.
In another embodiment, a ranges from 0.5 to 15, b ranges from 8.5 to 10, c ranges from 2.5 to 3.5, d ranges from 15.75 to 16.75, e ranges from 2.75 to 3.75, In various aspects, the critical rod diameter of the alloy is at least 6 mm. In other aspects, the notch toughness, defined as the stress intensity factor at crack initiation when measured on a 3 mm diameter rod containing a notch with length ranging from 1 to 2 mm and root radius ranging from 0.1 to 0.15 mm, is at least 55 MPa m^1/2.
In another embodiment, a ranges from 0.5 to 5, b ranges from 6.5 to 7.5, c ranges from 2.25 to 3.25, d ranges from 15.75 to 16.75, e ranges from 2.75 to 3.75. In various aspects, the critical rod diameter of the alloy is at least 6 mm. In other aspects the notch toughness, defined as the stress intensity factor at crack initiation when measured on a 3 mm diameter rod containing a notch with length ranging from 1 to 2 mm and root radius ranging from 0.1 to 0.15 mm, is at least 80 MPa m^1/2.
In another embodiment, a ranges from 0.5 to 10, b ranges from 8.5 to 10, c ranges from 2.5 to 3.5, d ranges from 15.75 to 16.75, and e ranges from 2.75 to 3.75. In various aspects, the critical rod diameter of the alloy is at least 6 mm. In other aspects, the notch toughness, defined as the stress intensity factor at crack initiation when measured on a 3 mm diameter rod containing a notch with length ranging from 1 to 2 mm and root radius ranging from 0.1 to 0.15 mm, is at least 60 MPa m^1/2.
In another embodiment, a ranges from 0.5 to 3, b ranges from 6.5 to 7.5, c ranges from 2.25 to 3.25, d ranges from 15.75 to 16.75, and e ranges from 2.75 to 3.75. In various aspects, the critical rod diameter of the alloy is at least 7 mm. In other aspects the notch toughness, defined as the stress intensity factor at crack initiation when measured on a 3 mm diameter rod containing a notch with length ranging from 1 to 2 mm and root radius ranging from 0.1 to 0.15 mm, is at least 90 MPa m^1/2.
In another embodiment, the difference between the crystallization temperature T_xand the glass transition temperature T_g, ΔT_x=T_x−T_g, measured at heating rate of 20 K/min, is at least 42° C.
In another embodiment, the difference between the crystallization temperature T_xand the glass transition temperature T_g, ΔT_x=T_x−T_g, measured at heating rate of 20 K/min, is at least 50° C.
In another embodiment, a ranges from 4 to 30, b ranges from 8 to 10.5, c ranges from 2.25 to 3.75, d ranges from 15.5 to 17, e ranges from 2.5 to 4, and wherein the alloy has a critical rod diameter of at least 5 mm, and wherein the difference between the crystallization temperature T_xand the glass transition temperature T_g, ΔT_x=T_x−T_g, measured at heating rate of 20 K/min, is at least 50° C.
In another embodiment, a ranges from 4 to 30, b ranges from 6 to 8, c ranges from 2 to 3.5, d ranges from 15.5 to 17, e ranges from 2.5 to 4, and wherein the critical rod diameter of the alloy is at least 5 mm, and wherein the difference between the crystallization temperature T_xand the glass transition temperature T_g, ΔT_x=T_x−T_g, measured at heating rate of 20 K/min, is at least 45° C.
In yet another embodiment, up to 2 atomic percent of Cr is substituted by Fe, Mn, W, Mo, Ru, Re, Cu, Pd, Pt, or combinations thereof.
In yet another embodiment, up to 2 atomic percent of Ni is substituted by Fe, Mn, W, Mo, Ru, Re, Cu, Pd, Pt, or combinations thereof.
In yet another embodiment, up to 1.5 atomic percent of Ta is substituted by Nb, V, or combinations thereof.
In yet another embodiment, the melt of the alloy is fluxed with a reducing agent prior to rapid quenching.
In yet another embodiment, the melt of the alloy is fluxed with boron oxide prior to rapid quenching.
In yet another embodiment, the temperature of the melt prior to quenching is at least 100° C. above the liquidus temperature of the alloy.
In yet another embodiment, the temperature of the melt prior to quenching is at least 1100° C.
The disclosure is also directed to an alloy having composition selected from a group consisting of: Ni₆₇Co_1.5Cr₉Ta₃P_16.25B_3.25, Ni_65.5CO₃Cr₉Ta₃P_16.25B_3.25, Ni_63.5CO₅Cr₉Ta₃P_16.25B_3.25, Ni_58.5CO₁₀Cr₉Ta₃P_16.25B_3.25, Ni_53.5Co₁₅Cr₉Ta₃P_16.25B_3.25, Ni_48.5CO₂₀Cr₉Ta₃P_16.25B_3.25, Ni_43.5Co₂₅Cr₉Ta₃P_16.25B_3.25, Ni_38.5CO₃₀Cr₉Ta₃P_16.25B_3.25, Ni_33.5CO₃₅Cr₉Ta₃P_16.25B_3.25, Ni_28.5Co₄₀Cr₉Ta₃P_16.25B_3.25, Ni_70.5Cr₇Ta_2.75P_16.25B_3.25, Ni₆₉Co_1.5Cr₇Ta_2.75P_16.25B_3.25, Ni_67.5CO₃Cr₇Ta_2.75P_16.25B_3.25, Ni_65.5CO₅Cr₇Ta_2.75P_16.25B_3.25, Ni_60.5Co₁₀Cr₇Ta_2.75P_16.25B_3.25, Ni_55.5Co₁₅Cr₇Ta_2.75P_16.25B_3.25, Ni_50.5CO₂₀Cr₇Ta_2.75P_16.25B_3.25, Ni_45.5CO₂₅Cr₇Ta_2.75P_16.25B_3.25, Ni_40.5CO₃₀Cr₇Ta_2.75P_16.25B_3.25, NI_45.5CO₃₅Cr₇Ta_2.75P_16.25B_3.25, and Ni_30.5Co₄₀Cr₇Ta_2.75P_16.25B_3.25. In various aspects, the critical rod diameter of the alloy is at least 3 mm.
In a further embodiment, a method is provided for forming a metallic glass object having a lateral dimension of at least 3 mm. The method includes melting an alloy into a molten state, the alloy comprising at least Ni, Co, Cr, Ta, P, and B with a formula Ni_{(100-a-b-c-d-e)}Co_aCr_bTa_cP_c/B_e, wherein a ranges from 0.5 to 40, b ranges from 3 to 11, c ranges from 1.5 to 4, d ranges from 14 to 17.5, and e ranges from 2 to 5. The method also includes quenching the molten alloy at a cooling rate sufficiently rapid to prevent crystallization of the alloy.
The disclosure is further directed to a metallic glass having any of the above formulas and/or formed of any of the foregoing alloys.
Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the disclosed subject matter. A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The description will be more fully understood with reference to the following figures and data graphs, which are presented as various embodiments of the disclosure and should not be construed as a complete recitation of the scope of the disclosure.

FIG. 1 provides a data plot showing the effect of varying the Ni and Co atomic percent on the glass forming ability of Ni_68.5-xCo_xCr₉Ta₃P_16.25B_3.25alloys, in accordance with embodiments of the present disclosure, for 0≦x≦45.

FIG. 2 provides a data plot showing the effect of varying the Ni and Co atomic percent on the notch toughness of Ni_68.5-xCo_xCr₉Ta₃P_16.25B_3.25metallic glasses, in accordance with embodiments of the present disclosure, for 0≦x≦45.

FIG. 3 provides an X-ray diffractogram verifying the amorphous structure of a 8 mm rod of a sample metallic glass Ni_65.5Co₃Cr₉Nb₃P_16.25B_3.25, in accordance with embodiments of the present disclosure, processed by water quenching the high temperature melt in a fused silica tube having a wall thickness of 1 mm.

FIG. 4 provides a data plot showing the effect of varying the Ni and Co atomic percent on the glass forming ability of Ni_70.5-xCo_xCr₇Ta_2.75P_16.25B_3.25alloys, in accordance with embodiments of the present disclosure, for 0≦x≦45.

FIG. 5 provides a data plot showing the effect of varying the Ni and Co atomic percent on the notch toughness of Ni_70.5-xCo_xCr₇Ta_2.75P_16.25B_3.25metallic glasses, in accordance with embodiments of the present disclosure, for 0≦x≦45.

FIG. 6 provides calorimetry scans for sample metallic glasses Ni_68.5-xCo_xCr₉Ta₃P_16.25B_3.25in accordance with embodiments of the present disclosure. The glass transition temperature T_g, crystallization temperature T_x, solidus temperature T_s, and liquidus temperature T_lare indicated by arrows.

FIG. 7 provides a data plot showing the effect of varying the Ni and Co atomic percent on the glass transition temperature T_g, crystallization temperature T_x, and difference ΔT_x=T_x−T_gof Ni_68.5-xCo_xCr₉Ta₃P_16.25B_3.25metallic glasses, in accordance with embodiments of the present disclosure, for 0≦x≦40.

FIG. 8 provides calorimetry scans for sample metallic glasses Ni_70.5-xCo_xCr₇Ta_2.75P_16.25B_3.25in accordance with embodiments of the present disclosure. The glass transition temperature T_g, crystallization temperature T_x, solidus temperature T_s, and liquidus temperature T_lare indicated by arrows.

FIG. 9 provides a data plot showing the effect of varying the Ni and Co atomic percent on the glass transition temperature T_g, crystallization temperature T_x, and difference ΔT_x=T_x−T_gof Ni_70.5-xCo_xCr₇Ta_2.75P_16.25B_3.25metallic glasses, in accordance with embodiments of the present disclosure, for 0≦x≦40.

DETAILED DESCRIPTION

The present disclosure is directed to alloys, metallic glasses, and methods of making and using the same. In some aspects, the alloys are described as capable of forming metallic glasses having certain characteristics. It is intended, and will be understood by those skilled in the art, that the disclosure is also directed to metallic glasses formed of the disclosed alloys described herein.
Definitions
In the present disclosure, the glass-forming ability of each alloy is quantified by the “critical rod diameter,” defined as the largest rod diameter in which the amorphous phase (i.e. the metallic glass) can be formed when processed by a method of water quenching a quartz tube having 0.5 mm thick walls containing a molten alloy.
A “critical cooling rate”, which is defined as the cooling rate required to avoid crystallization and form the amorphous phase of the alloy (i.e. the metallic glass), determines the critical rod diameter. The lower the critical cooling rate of an alloy, the larger its critical rod diameter. The critical cooling rate R_cin K/s and critical rod diameter d_cin mm are related via the following approximate empirical formula:
R_c=1000/d _c ² Eq. (2)
According to Eq. (2), the critical cooling rate for an alloy having a critical rod diameter of about 3 mm, as in the case of the alloys according to embodiments of the present disclosure, is only about 10²K/s.
Generally, three categories are known in the art for identifying the ability of an alloy to form glass (i.e. to bypass the stable crystal phase and form an amorphous phase). Alloys having critical cooling rates in excess of 10¹²K/s are typically referred to as non-glass formers, as it is physically impossible to achieve such cooling rates over a meaningful thickness (i.e. at least 1 micrometer). Alloys having critical cooling rates in the range of 10⁵to 10¹²K/s are typically referred to as marginal glass formers, as they are able to form glass over thicknesses ranging from 1 to 100 micrometers according to Eq. (2). Alloys having critical cooling rates on the order of 10³or less, and as low as 1 or 0.1 K/s, are typically referred to as bulk glass formers, as they are able to form glass over thicknesses ranging from 1 millimeter to several centimeters. The glass-forming ability of a metallic alloy is, to a very large extent, dependent on the composition of the alloy. The compositional ranges for alloys capable of forming marginal glass formers are considerably broader than those for forming bulk glass formers.
The “notch toughness,” defined as the stress intensity factor at crack initiation K_q, when measured on a 3 mm diameter rod containing a notch with length ranging from 1 to 2 mm and rot radius ranging from 0.1 to 0.15mm, is the measure of the material's ability to resist fracture in the presence of a notch. The notch toughness is a measure of the work required to propagate a crack originating from a notch. A high K_qensures that the material will be tough in the presence of defects.
The width of the supercooled region ΔT_xis defined as the difference between the crystallization temperature T_xand the glass transition temperature T_gof the metallic glass, ΔT_x=T_x−T_g, measured at heating rate of 20 K/min. A large ΔT_xvalue designates an ability of the metallic glass to be formed into an article by thermoplastic processing at temperatures above T_g.
Description of Alloy Compositions and Metallic Glass Compositions
In accordance with the provided disclosure and drawings, Ni—Co—Cr—Ta—P—B alloys and metallic glasses of Ni—Co—Cr—Ta—P—B alloys are provided within a well-defined compositional range requiring very low cooling rates to form metallic glasses, thereby allowing for bulk metallic glass formation such that metallic glass rods with critical rod diameters of at least 3 mm can be formed.
In some embodiments, Ni—Co—Cr—Ta—P—B alloys that fall within the compositional ranges of the disclosure can be represented by the following formula (subscripts denote atomic percent):
Ni_{(100-a-b-c-d-e)}Co_aCr_bTa_cP_aB_e Equation (1)
where a ranges from 0.5 to 40, b ranges from 3 to 11, c ranges from 1.5 to 4, d ranges from 14 to 17.5, and e ranges from 2 to 5.
In various aspects, the critical rod diameter of the alloy is at least 3 mm.
Samples of metallic glasses comprising alloys with compositions according to the formula Ni_68.5-xCo_xCr₉Ta₃P_16.25B_3.25, in accordance with embodiments of the present disclosure, are presented in Table 1. The critical rod diameters of sample alloys, along with the notch toughness of corresponding metallic glasses, are also listed in Table 1. Sample 1 with composition Ni_68.6Cr₈Nb₃P_16.25B_3.25is free of Co and is disclosed in U.S. patent application Ser. No. 14/081,622, exhibiting a critical rod diameter of 7 mm and a notch toughness of 51.8 MPa m^1/2.

TABLE 1

Sample alloys demonstrating the effect of increasing the Co atomic
concentration at the expense of Ni on the glass forming ability and
notch toughness of Ni_68.5−xCO_xCr₉Ta₃P_16.25B_3.25alloys

Sam-		Critical Rod	Notch Toughness
ple	Composition	Diameter [mm]	K_Q(MPa m^1/2)

1	Ni_68.5Cr₉Ta₃P_16.25B_3.25	7	51.8 ± 4.8
2	Ni₆₇Co_1.5Cr₉Ta₃P_16.25B_3.25	7	76.5 ± 11.0
3	Ni_65.5Co₃Cr₉Ta₃P_16.25B_3.25	8	71.5 ± 2.9
4	Ni_63.5Co₅Cr₉Ta₃P_16.25B_3.25	7	63.7 ± 3.2
5	Ni_58.5Co₁₀Cr₉Ta₃P_16.25B_3.25	6	67.0 ± 10.0
6	Ni_53.5Co₁₅Cr₉Ta₃P_16.25B_3.25	6	58.0 ± 5.6
7	Ni_48.5Co₂₀Cr₉Ta₃P_16.25B_3.25	5	40.2 ± 1.0
8	Ni_43.5Co₂₅Cr₉Ta₃P_16.25B_3.25	5	45.7 ± 2.1
9	Ni_38.5Co₃₀Cr₉Ta₃P_16.25B_3.25	5	38.2 ± 0.3
10	Ni_33.5Co₃₅Cr₉Ta₃P_16.25B_3.25	4	31.5 ± 5.0
11	Ni_28.5Co₄₀Cr₉Ta₃P_16.25B_3.25	3	—
12	Ni_23.5Co₄₅Cr₉Ta₃P_16.25B_3.25	1	—

FIG. 1 provides a data plot showing the effect of varying the Ni and Co atomic content x on the glass forming ability of alloys according to the composition formula Ni_68.5-xCo_xCr₉Ta₃P_16.25B_3.25. FIG. 2 provides a data plot showing the effect of varying the Ni and Co atomic content x on the notch toughness of metallic glasses according to the composition formula Ni_69-xCo_xCr_8.5Nb₃P_16.5B₃.
As shown in Table 1 and FIG. 1, alloys that satisfy the disclosed compositional range given by Eq (1) demonstrate a critical rod diameter of at least 3 mm. Also, as shown in Table 1 and FIGS. 1 and 2, when Co varies between 0.5 and 3 atomic percent, both the glass forming ability of the alloy and notch toughness of the metallic glass unexpectedly increase as compared to the Co-free alloy and metallic glass. Alloys and metallic glasses, according to the composition formula Ni_68.5-xCo_xCr₉Ta₃P_16.25B_3.25,with Co content between 0.5 and 3 atomic percent provide a good combination of high toughness and good glass forming ability. Specifically, alloy Ni_65.5Co₃Cr₉Ta₃P_16.25B_3.25(Sample 3) demonstrates a critical rod diameter of 8 mm and notch toughness of 71.5 MPa m^1/2, while the Co-free alloy Ni_68.5Cr₉Ta₃P_16.25B_3.25(Sample 1) demonstrates a critical rod diameter of 7 mm and notch toughness of 51.8 MPa m^1/2.
FIG. 3 provides an X-ray diffractogram verifying the amorphous structure of an 8 mm rod of sample metallic glass Ni_65.5Co₃Cr₉Ta₃P_16.25B_3.25(Sample 3) processed by water quenching the high temperature melt in a fused silica tube having a wall thickness of 1 mm.
Samples metallic glasses comprising alloys with compositions according to the formula Ni_70.5-xCo_xCr₇Ta_2.75P_16.25B_3.25are presented in Table 2. The critical rod diameters of the sample alloys, along with the notch toughness of the corresponding metallic glasses, are also listed in Table 2. Sample 13 with composition Ni_70.5Cr₇Ta_2.75P_16.25B_3.25is free of Co and is disclosed in the U.S. patent application Ser. No. 14/081,622, exhibiting a critical rod diameter of 7 mm and a notch toughness of 79.3 MPa m^1/2.

TABLE 2

Sample alloys demonstrating the effect of increasing the Co atomic
concentration at the expense of Ni on the glass forming ability and
notch toughness of Ni_70.5−xCo_xCr₇Ta_2.75P_16.25B_3.25alloys

Sam-		Critical Rod	Notch Toughness
ple	Composition	Diameter [mm]	K_Q(MPa m^1/2)

13	Ni_70.5Cr₇Ta_2.75P_16.25B_3.25	7	79.3 ± 5.6
14	Ni₆₉Co_1.5Cr₇Ta_2.75P_16.25B_3.25	7	94.4 ± 3.8
15	Ni_67.5Co₃Cr₇Ta_2.75P_16.25B_3.25	7	90.7 ± 0.5
16	Ni_65.5Co₅Cr₇Ta_2.75P_16.25B_3.25	6	74.5 ± 8.6
17	Ni_60.5Co₁₀Cr₇Ta_2.75P_16.25B_3.25	5	45.9 ± 4.6
18	Ni_55.5Co₁₅Cr₇Ta_2.75P_16.25B_3.25	5	58.4 ± 2.0
19	Ni_50.5Co₂₀Cr₇Ta_2.75P_16.25B_3.25	4	48.7 ± 3.0
20	Ni_45.5Co₂₅Cr₇Ta_2.75P_16.25B_3.25	4	44.9 ± 12.3
21	Ni_40.5Co₃₀Cr₇Ta_2.75P_16.25B_3.25	5	35.5 ± 9.2
22	Ni_45.5Co₃₅Cr₇Ta_2.75P_16.25B_3.25	3	—
23	Ni_30.5Co₄₀Cr₇Ta_2.75P_16.25B_3.25	2	—
24	Ni_25.5Co₄₅Cr₇Ta_2.75P_16.25B_3.25	1	—

FIG. 4 provides a data plot showing the effect of varying the Ni and Co atomic content x on the glass forming ability of alloys according to the composition formula Ni_70.5-xCo_xCr₇Ta_2.75P_16.25B_3.25. FIG. 5 provides a data plot showing the effect of varying the Ni and Co atomic percent x on the notch toughness of metallic glasses according to the composition formula Ni_70.5-xCo_xCr₇Ta_2.75P_16.25B_3.25.
Also, as shown in Table 2 and FIGS. 4 and 5, when Co varies between 0.5 and 3 atomic percent, the notch toughness of the metallic glass unexpectedly increases as compared to the Co-free alloy and metallic glass, while the glass forming ability remains unchanged. Specifically, alloy Ni₆₉Co_1.5Cr₇Ta_2.75P_16.25B_3.25(Sample 14) demonstrates a notch toughness of 94.4 MPa m^1/2and a critical rod diameter of 7 mm, while the Co-free alloy Ni_70.5Cr₇Ta_2.75P_16.25B_3.25(Sample 13) demonstrates a notch toughness of 93.9 MPa m^1/2and a critical rod diameter of 7 mm.
In other embodiments, Ni—Co—Cr—Ta—P—B metallic glasses according to Eq 1 of the present disclosure exhibit a difference between the crystallization temperature T_xand the glass transition temperature T_g, ΔT_x=T_x−T_g, measured at heating rate of 20 K/min, that is unexpectedly higher than the corresponding Co-free metallic glasses.
In some embodiments, when a ranges from 4 to 30, b ranges from 8 to 10.5, c ranges from 2.25 to 3.75, d ranges from 15.5 to 17, e ranges from 2.5 to 4, the difference between the crystallization temperature T_xand the glass transition temperature T_g, ΔT_x=T_x−T_g, measured at heating rate of 20 K/min, is at least 50° C.
FIG. 6 provides calorimetry scans for sample metallic glasses Ni_68.5-xCo_xCr₉Ta₃P_16.25B_3.25in accordance with embodiments of the present disclosure. The glass transition temperature T_g, crystallization temperature T_x, solidus temperature T_s, and liquidus temperature T_lare indicated by arrows in FIG. 6. Table 3 lists the glass transition temperature T_g, crystallization temperature T_x, solidus temperature T_s, and liquidus temperature T_lalong with the respective ΔT_xvalue for sample metallic glasses Ni_68.5-xCo_xCr₉Ta₃P_16.25B_3.25in accordance with embodiments of the present disclosure. FIG. 7 provides a data plot showing the effect of varying the Ni and Co atomic percent on the glass transition temperature T_g, crystallization temperature T_x, and difference ΔT_x=T_x−T_gof Ni_68.5-xCo_xCr₉Ta₃P_16.25B_3.25metallic glasses for 0.5≦x≦40.

TABLE 3

Effect of increasing the Co atomic concentration at the expense of Ni on the
glass-transition temperature, crystallization temperature, ΔT_x(=T_x− T_g), solidus temperature,
and liquidus temperature of Ni_68.5−xCo_xCr₉Ta₃P_16.25B_3.25alloys and metallic glasses

Sample	Composition	T_g(° C.)	T_x(° C.)	ΔT_x(K)	T_s(° C.)	T_l(° C.)

1	Ni_68.5Cr₉Ta₃P_16.25B_3.25	405.5	455.2	49.7	862.4	948.6
2	Ni₆₇Co_1.5Cr₉Ta₃P_16.25B_3.25	402.8	451.0	48.2	858.7	946.3
3	Ni_65.5Co₃Cr₉Ta₃P_16.25B_3.25	404.3	453.5	49.2	858.3	934.4
4	Ni_63.5Co₅Cr₉Ta₃P_16.25B_3.25	408.9	460.8	51.9	864.6	948.0
5	Ni_58.5Co₁₀Cr₉Ta₃P_16.25B_3.25	409.7	465.2	55.5	870.3	947.2
6	Ni_53.5Co₁₅Cr₉Ta₃P_16.25B_3.25	414.4	472.6	58.2	874.8	970.6
7	Ni_48.5Co₂₀Cr₉Ta₃P_16.25B_3.25	419.8	474.6	54.8	881.4	998.1
8	Ni_43.5Co₂₅Cr₉Ta₃P_16.25B_3.25	423.3	477.8	54.5	882.7	961.0
9	Ni_38.5Co₃₀Cr₉Ta₃P_16.25B_3.25	426.0	482.0	56.0	892.1	965.5
10	Ni_33.5Co₃₅Cr₉Ta₃P_16.25B_3.25	431.8	486.0	54.2	897.7	975.3
11	Ni_28.5Co₄₀Cr₉Ta₃P_16.25B_3.25	436.6	490.8	54.4	909.1	998.7

As shown in FIGS. 6 and 7 and Table 3, when the Co content is between 4 and 30 atomic percent, the ΔT_xvalues are unexpectedly larger compared to the value of the Co-free alloy. Specifically, the ΔT_xvalue for the Co-free metallic glass Ni_68.5Cr₉Ta₃F_16.25B_3.25(Sample 1) is 49.7° C., while the ΔT_xvalues for Ni_68.5-xCo_xCr₉Ta₃P_16.25B_3.25metallic glasses for 0.5≦x≦40 (Sample 2-11) are all larger than 50° C., and particularly the value for the metallic glass Ni_53.5Co₁₅Cr₉Ta₃P_16.25B_3.25(Sample 6) is 58.2° C.
In other embodiments, when a ranges from 4 to 30, b ranges from 6 to 8, c ranges from 2 to 3.5, d ranges from 15.5 to 17, e ranges from 2.5 to 4, the difference between the crystallization temperature T_xand the glass transition temperature T_g, ΔT_x=T_x−T_g, measured at heating rate of 20 K/min, is at least 45° C.
FIG. 8 provides calorimetry scans for sample metallic glasses Ni_70.5-xCo_xCr₇Ta_2.75P_16.25B_3.25in accordance with embodiments of the present disclosure. The glass transition temperature T_g, crystallization temperature T_x, solidus temperature T_s, and liquidus temperature T_lare indicated by arrows in FIG. 8. Table 4 lists the glass transition temperature T_g, crystallization temperature T_x, solidus temperature T_s, and liquidus temperature T_lalong with the respective ΔT_Xvalue for sample metallic glasses Ni_70.5-xCo_xCr₇Ta_2.75P_16.25B_3.25in accordance with embodiments of the present disclosure. FIG. 9 provides a data plot showing the effect of varying the Ni and Co atomic percent on the glass transition temperature T_g, crystallization temperature T_x, and difference ΔT_x=T_x−T_gof Ni_70.5-xCo_xCr₇Ta_2.75P_16.25B_3.25metallic glasses for 0.5≦x≦40.

TABLE 4

Effect of increasing the Co atomic concentration at the expense of Ni on the
glass-transition temperature, crystallization temperature, ΔT_x(=T_x− T_g), solidus temperature,
and liquidus temperature of Ni_70.5−xCo_xCr₇Ta_2.75P_16.25B_3.25alloys and metallic glasses

Sample	Composition	T_g(° C.)	T_x(° C.)	ΔT_x(K)	T_s(° C.)	T_l(° C.)

13	Ni_70.5Cr₇Ta_2.75P_16.25B_3.25	399.4	440.8	41.4	860.4	911.9
14	Ni₆₉Co_1.5Cr₇Ta_2.75P_16.25B_3.25	400.0	443.1	43.1	857.6	939.0
15	Ni_67.5Co₃Cr₇Ta_2.75P_16.25B_3.25	398.0	443.7	45.7	859.0	944.3
16	Ni_65.5Co₅Cr₇Ta_2.75P_16.25B_3.25	402.3	451.2	48.9	862.9	943.0
17	Ni_60.5Co₁₀Cr₇Ta_2.75P_16.25B_3.25	403.1	452.5	49.4	867.3	946.0
18	Ni_55.5Co₁₅Cr₇Ta_2.75P_16.25B_3.25	409.3	458.6	49.3	875.6	945.7
19	Ni_50.5Co₂₀Cr₇Ta_2.75P_16.25B_3.25	413	460.6	47.6	879.1	949.3
20	Ni_45.5Co₂₅Cr₇Ta_2.75P_16.25B_3.25	419.9	466.1	46.2	885.8	970.6
21	Ni_40.5Co₃₀Cr₇Ta_2.75P_16.25B_3.25	424.6	469.5	44.9	892.4	1000.2
22	Ni_45.5Co₃₅Cr₇Ta_2.75P_16.25B_3.25	422.7	471.1	48.4	901.9	1016.5
23	Ni_30.5Co₄₀Cr₇Ta_2.75P_16.25B_3.25	427.5	474.0	46.5	910.0	1038.4

As shown in FIGS. 8 and 9 and Table 4, when the Co atomic percent is between 4 and 30 atomic percent, the ΔT_xvalues are unexpectedly larger compared to the value of the Co-free alloy. Specifically, the ΔT_xvalue for the Co-free metallic glass Ni_70.5Cr₇Ta_2.75P_16.25B_3.25(Sample 13) is 41.4° C., while the ΔT_xvalues for Ni_70.5-xCo_xCr₇Ta_2.75P_16.25B_3.25metallic glasses for 0.5≦x≦40 (Examples 14-23) are all larger than 42° C., while the ΔT_xvalues for 0.5≦x≦40 (Sample 16-23) are all larger than 45° C. Particularly the ΔT_xvalue for the metallic glass Ni_60.5Co₁₀Cr₇Ta_2.75P_16.25B_3.25(Sample 17) is 49.4° C.
Description of Methods of Processing the Sample Alloys
A method for producing the alloy ingots involves inductive melting of the appropriate amounts of elemental constituents in a quartz tube under inert atmosphere. The purity levels of the constituent elements were as follows: Ni 99.995%, Co 99.995%, Cr 99.996%, Ta 99.95%, P 99.9999%, and B 99.5%. The melting crucible may alternatively be a ceramic such as alumina or zirconia, graphite, sintered crystalline silica, or a water-cooled hearth made of copper or silver.
A particular method for producing metallic glass rods from the alloy ingots for the sample alloys of Tables 1 and 2 involves re-melting the alloy ingots in quartz tubes having 0.5-mm thick walls in a furnace at 1100° C. or higher, and in some embodiments, ranging from 1150° C. to 1400° C., under high purity argon and rapidly quenching in a room-temperature water bath. Alternatively, the bath could be ice water or oil. Metallic glass articles can be alternatively formed by injecting or pouring the molten alloy into a metal mold. The mold can be made of copper, brass, or steel, among other materials.
Optionally, prior to producing an metallic glass article, the alloyed ingots may be fluxed with a reducing agent by re-melting the ingots in a quartz tube under inert atmosphere, bringing the alloy melt in contact with the molten reducing agent, and allowing the two melts to interact for about 1000 s at a temperature of about 1200° C. or higher, under inert atmosphere and subsequently water quenching.

Test Methodology for Assessing Glass-Forming Ability

The glass-forming ability of each alloy was assessed by determining the maximum rod diameter in which the amorphous phase of the alloy (i.e. the metallic glass phase) could be formed when processed by the method described above; namely water quenching a quartz tube having 0.5 mm thick walls containing a molten alloy. X-ray diffraction with Cu—Kα radiation was performed to verify the amorphous structure of the alloys.

Test Methodology for Differential Scanning Calorimetry

Differential scanning calorimetry was performed on sample metallic glasses at a scan rate of 20 K/min to determine the glass-transition, crystallization, solidus, and liquidus temperatures of sample metallic glasses.

Test Methodology for Measuring Notch Toughness

The “notch toughness,” defined as the stress intensity factor at crack initiation K_q, when measured on a 3 mm diameter rod containing a notch with length ranging from 1 to 2 mm and rot radius ranging from 0.1 to 0.15 mm, quantifies the material's ability to resist fracture in the presence of a notch. The notch toughness is a measure of the work required to propagate a crack originating from a notch. A high K_qensures that the material will be tough in the presence of defects.
The notch toughness of sample metallic glasses was performed on 3-mm diameter rods. The rods were notched using a wire saw with a root radius ranging from 0.10 to 0.13 mm to a depth of approximately half the rod diameter. The notched specimens were tested on a 3-point beam configuration with span of 12.7 mm, and with the notched side carefully aligned and facing the opposite side of the center loading point. The critical fracture load was measured by applying a monotonically increasing load at constant cross-head speed of 0.001 mm/s using a screw-driven testing frame. At least three tests were performed, and the variance between tests is included in the notch toughness plots. The stress intensity factor for the geometrical configuration employed here was evaluated using the analysis by Murakimi (Y. Murakami, Stress Intensity Factors Handbook, Vol. 2, Oxford: Pergamon Press, p. 666 (1987)).
The disclosed Ni—Co—Cr—Ta—P—B alloys and metallic glasses with controlled ranges within the disclosed composition range demonstrate a combination of good glass forming ability, high toughness, and large ΔT_xvalues. The disclosed alloys have critical rod diameters of at least 3 mm and up to about 8 mm or greater when processed by the particular method described herein. Certain alloys with very good glass forming ability also have high notch toughness approaching 100 MPa m^1/2, and ΔT_xvalues approaching 60° C. The combination of good glass-forming ability, high toughness, and large ΔT_xvalues makes the present Ni—Co—Cr—Ta—P—B alloys and metallic glasses comprising Ni—Co—Cr—Ta—P—B alloys excellent candidates for various engineering applications. Among many applications, the disclosed alloys may be used in consumer electronics, dental and medical implants and instruments, luxury goods, and sporting goods applications.
Having described several embodiments, it will be recognized by those skilled in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present invention. Accordingly, the above description should not be taken as limiting the scope of the invention.
Those skilled in the art will appreciate that the presently disclosed embodiments teach by way of example and not by limitation. Therefore, the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall therebetween

Claims

What is claimed is:

1. An alloy capable of forming a metallic glass represented by the following formula (subscripts denote atomic percentages):

Ni_{(100-a-b-c-d-e)}Co_aCr_bTa_cP_aB_e

where:

a ranges from 0.5 to 40, b ranges from 3 to 11, c ranges from 1.5 to 4, d ranges from 14 to 17.5, and e ranges from 2 to 5, and

wherein the alloy has a critical rod diameter of at least 3 mm.

2. The alloy of claim 1 wherein c is determined by x+y·b, where x is between 1.5 and 2 and y is between 0.1 and 0.15.

3. The alloy of claim 1 wherein a ranges from 0.5 to 30, b ranges from 8 to 10.5, c ranges from 2.25 to 3.75, d ranges from 15.5 to 17, e ranges from 2.5 to 4, and wherein the critical rod diameter of the alloy is at least 5 mm.

4. The alloy of claim 1 wherein a ranges from 0.5 to 15, b ranges from 8.5 to 10, c ranges from 2.5 to 3.5, d ranges from 15.75 to 16.75, e ranges from 2.75 to 3.75, and wherein the critical rod diameter of the alloy is at least 6 mm.

5. The alloy of claim 1 wherein a ranges from 0.5 to 30, b ranges from 6 to 8, c ranges from 2 to 3.5, d ranges from 15.5 to 17, e ranges from 2.5 to 4, and wherein the critical rod diameter of the alloy is at least 5 mm.

6. The alloy of claim 1 wherein a ranges from 0.5 to 5, b ranges from 6.5 to 7.5, c ranges from 2.25 to 3.25, d ranges from 15.75 to 16.75, e ranges from 2.75 to 3.75, and wherein the critical rod diameter of the alloy is at least 6 mm.

7. The alloy of claim 1 wherein the difference between the crystallization temperature Tx and the glass transition temperature Tg, ΔTx=Tx−Tg, measured at heating rate of 20 K/min, is at least 42° C.

8. The alloy of claim 1 wherein the difference between the crystallization temperature Tx and the glass transition temperature Tg, ΔTx=Tx−Tg, measured at heating rate of 20 K/min, is at least 50° C.

9. The alloy of claim 1 wherein up to 2 atomic percent of Cr is substituted by Fe, Mn, W, Mo, Ru, Re, Cu, Pd, Pt, or combinations thereof.

10. The alloy of claim 1 wherein up to 2 atomic percent of Ni is substituted by Fe, Mn, W, Mo, Ru, Re, Cu, Pd, Pt, or combinations thereof.

11. The alloy of claim 1 wherein up to 1.5 atomic percent of Ta is substituted by Nb, V, or combinations thereof.

12. A metallic glass comprising an alloy of claim 1.

13. The metallic glass of claim 12 wherein a ranges from 0.5 to 15, b ranges from 8.5 to 10, c ranges from 2.5 to 3.5, d ranges from 15.75 to 16.75, e ranges from 2.75 to 3.75; wherein the critical rod diameter of the alloy is at least 6 mm; and wherein the notch toughness is at least 55 MPa m^1/2.

14. The metallic glass of claim 12 wherein a ranges from 0.5 to 5, b ranges from 6.5 to 7.5, c ranges from 2.25 to 3.25, d ranges from 15.75 to 16.75, e ranges from 2.75 to 3.75; wherein the critical rod diameter of the alloy is at least 6 mm; and wherein the notch toughness is at least 80 MPa m^1/2.

15. The metallic glass of claim 12 wherein a ranges from 0.5 to 10, b ranges from 8.5 to 10, c ranges from 2.5 to 3.5, d ranges from 15.75 to 16.75, e ranges from 2.75 to 3.75; wherein the critical rod diameter of the alloy is at least 6 mm; and wherein the notch toughness is at least 60 MPa m^1/2.

16. The metallic glass of claim 12 wherein a ranges from 0.5 to 3, b ranges from 6.5 to 7.5, c ranges from 2.25 to 3.25, d ranges from 15.75 to 16.75, e ranges from 2.75 to 3.75; wherein the critical rod diameter of the alloy is at least 7 mm; and wherein the notch toughness is at least 90 MPa m^1/2.

17. A method of producing the metallic glass of claim 12 comprising:

melting the alloy into a molten state; and

quenching the melt at a cooling rate sufficiently rapid to prevent crystallization of the alloy.

18. The method of claim 17, further comprising fluxing the melt with a reducing agent prior to quenching.

19. The method of claim 18, wherein the reducing agent is boron oxide.

20. The method of claim 17, wherein the melt prior to quenching is heated to at least 1100° C.