Co-based high-strength amorphous alloy and use thereof
11555228 · 2023-01-17
Assignee
Inventors
Cpc classification
C22C32/0047
CHEMISTRY; METALLURGY
International classification
C22C32/00
CHEMISTRY; METALLURGY
Abstract
The present invention relates to an amorphous alloy corresponding to the formula:
Co.sub.aNi.sub.bMo.sub.c(C.sub.1-xB.sub.x).sub.dX.sub.e
wherein X is one or several elements selected from the group consisting of Cu, Si, Fe, P, Y, Er, Cr, Ga, Ta, Nb, V and W; wherein the indices a to e and x satisfy the following conditions: 55≤a≤75 at. % 0≤b≤15 at. % 7≤c≤17 at. % 15≤d≤23 at. % 0.1≤x≤0.9 at. % 0≤e≤10 at. %, each element selected from the group having a content≤3 at. % and preferably ≤2 at. %, the balance being impurities.
Claims
1. An amorphous alloy consisting of the formula:
Co.sub.aNi.sub.bMo.sub.c(C.sub.1-xB.sub.x).sub.dX.sub.e wherein X is one or several elements selected from the group consisting of Cu, Si, Fe, P, Y, Er, Cr, Ga, Ta, Nb, V and W; wherein the indices a to e and x satisfy the following conditions: 60≤a≤70 at. % 0≤b≤10 at. % 10≤c≤15 at. % 17≤d≤21 at. % 0.1≤x≤0.45 0≤e≤5 at. %, each element selected from the group having a content below ≤3 at. %, the balance being impurities, wherein the amorphous alloy does not break when folded 180° when the amorphous alloy is in the form of a ribbon having a thickness of 80 μm.
2. The amorphous alloy according to claim 1, wherein 0≤e≤3 at. %.
3. The amorphous alloy according to claim 1, wherein Cr content=0 at. %.
4. The amorphous alloy according to claim 1, wherein Fe content=0 at. %.
5. The amorphous alloy according to claim 1, wherein Cu content is ≤1 at. %.
6. The amorphous alloy according to claim 1, having a fracture strength under compressive loading above 3750 mPa.
7. The amorphous alloy according to claim 1 comprising α-Co precipitates.
8. A ribbon, wire or foil made of the amorphous alloy according to claim 1, having a thickness or diameter above 80 μm.
9. A watch component made of the amorphous alloy according to claim 1.
10. A watch comprising the watch component according to claim 9.
11. The amorphous alloy according to claim 1, wherein 0≤e≤5 at. %, each element selected from the group having a content≤2 at. %.
12. The amorphous alloy according to claim 1, having a fracture strength under compressive loading above 4000 mPa.
13. A ribbon, wire or foil made of the amorphous alloy according to claim 1, having a thickness or diameter above 100 μm.
14. A spring made of the amorphous alloy according to claim 1.
15. The amorphous alloy according to claim 1, wherein 0.1≤x≤0.33.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1)
DETAILED DESCRIPTION OF THE INVENTION
(2) The invention relates to a Co-based amorphous alloy. By amorphous alloy is meant a fully amorphous alloy or a partially amorphous alloy with a volume fraction of amorphous phase higher than 50%. This amorphous alloy corresponds to the following formula:
Co.sub.aNi.sub.bMo.sub.c(C.sub.1-xB.sub.x).sub.dX.sub.e
wherein X is one or several elements selected from the group consisting of Cu, Si, Fe, P, Y, Er, Cr, Ga, Ta, Nb, V and W;
wherein the indices a to e and x satisfy the following conditions:
(3) 55≤a≤75 at. %, preferably 60≤a≤70 at. %,
(4) 0≤b≤15 at. %, preferably 0≤b≤10 at. %,
(5) 7≤c≤17 at. %, preferably 10≤c≤15 at. %,
(6) 15≤d≤23 at. %, preferably 17≤d≤21 at. %,
(7) 0.1≤x≤0.9
(8) 0≤e≤10 at. %, preferably 0≤e≤5 at. % and more preferably 0≤e≤3 at. %, each element selected from the group having a content below 3 at. % and preferably below 2 at. %,
(9) the balance being impurities with a maximum of 2 at. %.
(10) In the impurities are included small amounts (≤0.5 at. %) of oxygen or nitrogen.
(11) This amorphous alloy can be synthesized as thick ribbon, thick foil, wire or more generally as small bulk specimen, with a minimum thickness of 80 μm and preferably of 100 μm.
(12) The amorphous alloy exhibits a fracture strength above 3.75 GPa and preferably above 4 GPa and a large plastic elongation above 3% under compressive loading. It also exhibits high ductility under 180° bend tests for specimens with a thickness above 80 μm.
(13) These properties make them particularly suitable for manufacturing watch components like springs by cold forming.
(14) The process for manufacturing the amorphous alloy may be any conventional process such as melt-spinning, twin-roll casting, planar flow casting or further rapid cooling processes. Although not required, the process may comprise a subsequent step of heat treatment. This heat treatment can be carried out at temperatures below T.sub.g for relaxation or change in free volume, in the supercooled liquid region ΔT.sub.x or slightly above T.sub.x1. A heat treatment of the alloy above T.sub.g can be carried out to nucleate a certain fraction of nanoscale precipitates like α-Co precipitates. The alloy can also be subjected to cryogenic thermal cycling in order to achieve a rejuvenation of the amorphous matrix.
(15) Hereinafter, the present invention is described in further detail through examples.
EXAMPLES
(16) Experimental Procedure
(17) Sample Preparation
(18) The master alloys were prepared in an alumina or quartz crucible by induction melting mixtures of pure Co, Fe, Cr, Ni, Mo, graphite (99.9 wt. %) and pre-alloys of Co.sub.80B.sub.20 (99.5 wt. %). If necessary, the ingots were homogenized by arc-melting. Ribbons with thicknesses between 55 and 160 μm and widths in the range of 1 and 5 mm were subsequently fabricated from the master alloys by the Chill-Block Melt Spinning (CBMS) technique with a single-roller melt-spinner. The process atmosphere was inert gas or CO.sub.2. In general, for a ribbon thickness t>100 μm, a wheel speed≤13 mm/s had to be applied.
(19) Sample Characterization
(20) The ribbons were evaluated with respect to their thermal, structural and mechanical properties by differential scanning calorimetry (DSC) at a constant heating rate of 20 K/min and under a flow of purified argon, by X-ray diffraction analyses, by optical stereoscopy and by mechanical testing. The X-ray measurements were performed in reflection configuration with Co—Kα radiation and within a range of 2θ=20 . . . 80° or 10 . . . 100°.
(21) Selected material variants with sufficient glass-forming ability were cast to ∅1 mm rods with a final aspect ratio of 2:1 to determine their mechanical properties under quasi-static compressive loading ({dot over (ε)}=10.sup.−4s.sup.−1) as recommended by ASTM E9, using an electromechanical universal testing machine. At least three specimens were tested for the selected compositions.
(22) To estimate the strength and failure strain of glassy ribbons, additional two-point bending tests were carried out. This test was first developed for optical glass fibers and finally applied on melt-spun ribbons (see for example WO 2010 027813). In this test, the ribbon is bent into a “U” shape and subjected to a constrained compressive loading between two co-planar and polished faceplates until fracture (one faceplate stationary). The two-point bending tests were carried out by means of a miniaturized computer-controlled tensile/compressive device at a constant traverse speed of 5 μm/s. The stop of the motor movement due to the fracture of the tape was achieved by adjusting a defined load drop criterion (viz, load decrease of 10% relative to the maximum load). The failure strength σ.sub.b, f of the specimen is described by the maximum tensile load F.sub.max in the outer surface given from the faceplace separation at fracture D.sub.f:
(23)
where E is the Young's modulus, t the thickness and I the second moment of cross-sectional area (I=bt.sup.3/12) of the ribbons. For the calculation of the failure strength in the examples, a Young's modulus of E.sub.av=155 GPa, indicating an average value derived from the elastic slopes of the load versus displacement curves, has been used.
(24) Based on the assumption that the tape undergoes an elastic deformation until fracture, the failure strain can be directly calculated by
(25)
(26) Even if plastic deformation occurs, this method still provide a relative measure of strength. For each alloy, at least three samples of a same thickness were tested. It is the free side of the ribbons, i.e. the side not in contact with the wheel's surface, that was subject to the tension.
(27) Additionally, primitive 180° bend tests were applied on ribbons of different compositions and thicknesses inducing a high strain in their outer fiber loaded under tension. The ribbon is considered to be ductile if it does not break when folded at 180°. The bending ability of the specimens has been tested for both sides of the ribbon for each specimen.
(28) Moreover, nanoindentation measurements were conducted to evaluate and distinguish the ribbons with respect to their stiffness, hardness and performed deformation work. The nanoindentation experiments were carried on polished flat specimens at room temperature in the load control mode by using a UNAT nanoindenter (ASMEC laboratories) equipped with a triangular diamond Berkovich tip. A maximum load of 3 mN as well as a constant strain rate of 0.046 s.sup.−1 were applied. On each sample at least 10 indents for every loading were placed in a linear array and in a distance of 20 μm. The hardness and reduced elastic modulus values were derived from the unloading part of the load vs. displacement curves according to Oliver and Pharr's principle (W. C. Oliver, and G. M. Pharr, “An improved technique for determining hardness and elastic-modulus using load and displacement sensing indentation experiments,”J. Mater. Res., 7(6):1564-1583, 1992) and considering the corrections with regard to thermal drift, contact area (calibrated with a fused quartz plate), instrument compliance, initial penetration depth (zero point correction), lateral elastic displacement of the sample surface (radial displacement correction) and contact stiffness. Hence, the elastic reduced modulus E.sub.r is determined by
E.sub.r=(√πS)/(2βA.sub.c.sup.1/2)
where S is the contact stiffness of the sample, β is a constant depending on the indenter geometry and A.sub.c, is the projected area of contact for the indentation depth h.sub.c=h.sub.max−εP.sub.max/S with a maximal displacement h.sub.max at maximum load P.sub.max. β and ε are tip-dependent constants, given by β=1.05 (W. C. Oliver, and G. M. Pharr, “Measurement of hardness and elastic modulus by instrumented indentation: Advances in understanding and refinements to methodology,” J. Mater. Res., 19(1):3-20, 2004) and ε=0.75 (ISO 14577-1:2015. Metallic materials—Instrumented indentation test for hardness and materials parameters Part 1: Test method, 2015). The equivalent Vickers HV hardness is correlated to the indentation hardness H.sub.IT=P.sub.max/A.sub.c by the following term:
HV(GPα)=0.92671H.sub.IT.
(29) However, the hardness calculated by nanoindentation depends on the loading rate and the maximum applied load, and due to the indentation-size effect often not reflects the hardness values from macro- or microhardness measurements.
(30) The deformation energies during nanoindentation were determined from the areas between the unloading curve and the x-axis (elastic deformation energy, U.sub.el) and between the loading curve and the x-axis (total deformation work, U.sub.tot). Therefore, the plastic deformation energy, U.sub.p can be derived from the relationship U.sub.t-U.sub.el.
(31) Results
(32) Table 1 below lists the tested Co—Mo—C—B—X as-cast ribbons processed under vacuum/argon atmosphere (chamber pressure of 300 mbar). The alloy compositions include comparative examples and examples according to the invention. In the comparative alloys, the Cr content ranges from 5 to 15 atomic percent and the alloy may additionally comprise Fe with a content of 5 atomic percent. In the alloys according to the invention, the Fe and Cr contents are reduced and even suppressed to improve the ductility whilst keeping high fracture strength as shown hereafter.
(33) In Table 1, the DSC data related to the onsets of glass transition (T.sub.g) and primary crystallization (T.sub.x1), the melting (T.sub.m) and liquidus temperatures (T.sub.liq) as well as the width of the supercooled liquid region (ΔT.sub.x) are given.
(34) For all the ribbons, the microstructures are fully amorphous or partially amorphous with the presence of some crystallites containing at least α-Co precipitates for the compositions Co.sub.60Ni.sub.5Mo.sub.14C.sub.18B.sub.3, Co.sub.60.6Ni.sub.9.15Mo.sub.10.1C.sub.14B.sub.4Si.sub.1.9Cu.sub.0.17, Co.sub.61.4Ni.sub.5.2Mo.sub.14.33C.sub.14.3B.sub.3Si.sub.1.7Cu.sub.0.07 and Co.sub.69Mo.sub.10C.sub.14B.sub.7 and mostly carbide and boride phases for the (Co.sub.60Ni.sub.5Mo.sub.14C.sub.15B.sub.6).sub.99V.sub.1. For the alloys of the invention, the structures are amorphous for a thickness of minimum 80 μm.
(35) Table 2 summarizes the mechanical properties under quasi-static compressive loading at room temperature for some samples. The reduction of the Cr content results in a significant increase in plasticity combined with a minor degradation of the ultimate fracture strength. The iron content was kept below 5% in order to keep the total Poisson's ratio (and hence the ductility of the alloy) as high as possible. The mechanical responses of the Co.sub.60Ni.sub.5Mo.sub.14C.sub.15+xB.sub.6-x alloys are characterized by a very high maximum stress level above 3.75 GPa with a pronounced plastic deformation. By taking the fully amorphous Co.sub.60Ni.sub.5Mo.sub.14C.sub.15+xB.sub.6-x rods as example, average values of σ.sub.c,y=3959 MPa, σ.sub.c, f=4262 MPa and ε.sub.c, pl=6.3% were determined.
(36) The experimental results of the two-point bending tests and 180° bending tests on as-cast ribbons are listed in Tables 3 and 4 respectively. As shown in Table 3, failure strength higher than 4500 MPa is obtained for the alloys according to the invention. As seen from Table 4, the alloys according to the invention exhibit bendability for ribbons with a thickness higher than 80 μm and even higher than 100 μm.
(37) TABLE-US-00001 TABLE 1 Alloy t (μm) Structure T.sub.g (K) T.sub.x1 (K) ΔT.sub.x (K) T.sub.m (K) T.sub.liq (K) Comparative Co.sub.45Fe.sub.5Cr.sub.15Mo.sub.14C.sub.10B.sub.11 56 Am. 829 922 93 1382 1457 examples Co.sub.45Fe.sub.5Cr.sub.10Ni.sub.5Mo.sub.14C.sub.10B.sub.11 62 Am. 799 876 77 1352 1403 Co.sub.45Fe.sub.5Cr.sub.5Ni.sub.10Mo.sub.14C.sub.10B.sub.11 59 Am. 763 806 43 1405 1430 Co.sub.50Cr.sub.10Ni.sub.5Mo.sub.14C.sub.10B.sub.11 133 Am. 805 879 74 1348 1399 Co.sub.50Cr.sub.5Ni.sub.10Mo.sub.14C.sub.10B.sub.11 94 Am. 779 836 57 1341 1402 Examples of Co.sub.60Ni.sub.5Mo.sub.14C.sub.15B.sub.6 130 Am. 745 788 43 1396 1436 the invention Co.sub.60Ni.sub.5Mo.sub.14C.sub.16B.sub.5 133 Am. 745 794 49 1396 1433 Co.sub.60Ni.sub.5Mo.sub.14C.sub.17B.sub.4 83 Am. 748 795 47 — — Co.sub.60Ni.sub.5Mo.sub.14C.sub.18B.sub.3 133 Am./cryst.* 739 778 39 1396 1443 Co.sub.60Ni.sub.9Mo.sub.10C.sub.15B.sub.4Si.sub.2 94 Am. 668 695 27 1399 — (Co.sub.60Ni.sub.5Mo.sub.14C.sub.15B.sub.6).sub.99V.sub.1 110 Am./cryst.** 763 815 52 — — Co.sub.60.6Ni.sub.9.16Mo.sub.10.1C.sub.14B.sub.4Si.sub.1.9Cu.sub.0.17 158 Am./cryst.* 676 694 18 1405 1453 Co.sub.60.44Ni.sub.5.1Mo.sub.14.04C.sub.14.1B.sub.4Si.sub.1.96Cu.sub.0.36 138 Am. 723 747 24 1402 1443 Co.sub.61.4Ni.sub.5.2Mo.sub.14.33C.sub.14.3B.sub.3Si.sub.1.7Cu.sub.0.07 150 Am./cryst.* 714 760 46 1399 1458 Co.sub.64Ni.sub.5Mo.sub.10C.sub.15B.sub.6 125 Am. 702 717 15 1396 1425 Co.sub.65Mo.sub.14C.sub.15B.sub.6 118 Am. 767 820 53 — — Co.sub.65Mo.sub.14C.sub.17B.sub.4 86 Am. 766 812 46 — — Co.sub.69Mo.sub.10C.sub.15B.sub.6 100 Am. 732 776 44 — — Co.sub.69Mo.sub.10C.sub.14B.sub.7 107 Am./cryst.* 737 779 42 — — Am. = X-ray fully amorphous, cryst. = presence of crystallites, *= α-Co precipitates, **= Mostly carbides and borides
(38) TABLE-US-00002 TABLE 2 σ.sub.c,γ σ.sub.c,f Alloy (MPa) (MPa) ε.sub.c,pl (%) Comparative Co.sub.45Fe.sub.5Cr.sub.15Mo.sub.14C.sub.10B.sub.11 4232 4659 1.3 examples Co.sub.45Fe.sub.5Cr.sub.10Ni.sub.5Mo.sub.14C.sub.10B.sub.11 4278 4587 2.2 Co.sub.45Fe.sub.5Cr.sub.5Ni.sub.10Mo.sub.14C.sub.10B.sub.11 4146 4484 3.1 Co.sub.50Cr.sub.10Ni.sub.5Mo.sub.14C.sub.10B.sub.11 4193 4571 2.5 Co.sub.50Cr.sub.5Ni.sub.10Mo.sub.14C.sub.10B.sub.11 4238 4369 1.8 Example of Co.sub.60Ni.sub.5Mo.sub.14C.sub.15B.sub.6 3959 4262 6.3 the invention
(39) TABLE-US-00003 TABLE 3 t E D.sub.f σ.sub.b,f ε.sub.b,f Alloy (μm) Structure (GPa) (mm) (MPa) (%) Examples Co.sub.60Ni.sub.5Mo.sub.14C.sub.16B.sub.5 123 Am. 155 4.15 5500 3.64 of the Co.sub.60.44Ni.sub.5.1Mo.sub.14.04C.sub.14.1B.sub.4Si.sub.1.96Cu.sub.0.36 115 Am. 155 3.48 5860 3.65 invention Co.sub.61.4Ni.sub.5.2Mo.sub.14.33C.sub.14.3B.sub.3Si.sub.1.7Cu.sub.0.07 94 Am./cryst. 155 3.74 4880 3.09 108 Am./cryst. 155 4.36 4790 3.31
(40) TABLE-US-00004 TABLE 4 Bendability Processing (free side and Alloy t (μm) atmosphere Structure wheel side) Comparative Co.sub.45Fe.sub.5Cr.sub.15Mo.sub.14C.sub.10B.sub.11 49-56 Vacuum/Ar Am. No examples Co.sub.45Fe.sub.5Cr.sub.10Ni.sub.5Mo.sub.14C.sub.10B.sub.11 53-54 Vacuum/Ar Am. No Co.sub.45Fe.sub.5Cr.sub.5Ni.sub.10Mo.sub.14C.sub.10B.sub.11 60-61 Vacuum/Ar Am. No Co.sub.50Cr.sub.10Ni.sub.5Mo.sub.14C.sub.10B.sub.11 54-67 Vacuum/Ar Am. No 66-67 CO.sub.2 Am. No Co.sub.50Cr.sub.5Ni.sub.10Mo.sub.14C.sub.10B.sub.11 78-90 Vacuum/Ar Am. No 91-94 CO.sub.2 Am. No Examples of the Co.sub.60Ni.sub.5Mo.sub.14C.sub.15B.sub.6 99-105 Vacuum/Ar Am. Yes invention 92-116 CO.sub.2 Am. Yes Co.sub.60Ni.sub.5Mo.sub.14C.sub.16B.sub.5 118-133 Vacuum/Ar Am. Yes Co.sub.60Ni.sub.5Mo.sub.14C.sub.17B.sub.4 65-89 Vacuum/Ar Am. Yes Co.sub.60Ni.sub.5Mo.sub.14C.sub.18B.sub.3 105-133 Vacuum/Ar Am./cryst. Yes Co.sub.60Ni.sub.9Mo.sub.10C.sub.15B.sub.4Si.sub.2 83-94 Vacuum/Ar Am. Yes (Co.sub.60Ni.sub.9Mo.sub.10C.sub.15B.sub.6).sub.99V.sub.1 110-133 Vacuum/Ar Am./cryst. Yes Co.sub.60.6Ni.sub.9.15Mo.sub.10.1C.sub.14B.sub.4Si.sub.1.9Cu.sub.0.17 113-158 Vacuum/Ar Am./cryst. Yes Co.sub.60.44Ni.sub.5.1Mo.sub.14.04C.sub.14.1B.sub.4Si.sub.1.96Cu.sub.0.36 79-84 Vacuum/Ar Am. Yes Co.sub.61.4Ni.sub.5.2Mo.sub.14.33C.sub.14.3B.sub.3Si.sub.1.7Cu.sub.0.07 94-100 Vacuum/Ar Am./cryst. Yes Co.sub.64Ni.sub.5Mo.sub.10C.sub.15B.sub.6 92-125 Vacuum/Ar Am. Yes Co.sub.65Mo.sub.14C.sub.15B.sub.6 81-118 Vacuum/Ar Am. Yes Co.sub.65Mo.sub.14C.sub.17B.sub.4 79-86 Vacuum/Ar Am. Yes Co.sub.69Mo.sub.10C.sub.15B.sub.6 90-100 Vacuum/Ar Am. Yes Co.sub.69Mo.sub.10C.sub.14B.sub.7 87-107 Vacuum/Ar Am./cryst. Yes
(41) The nanoindentation tests were conducted on the as-cast and polished ribbons of the compositions Co.sub.50Cr.sub.10Ni.sub.5Mo.sub.14C.sub.10B.sub.11, Co.sub.60Ni.sub.5Mo.sub.14C.sub.16B.sub.5, Co.sub.60.44Ni.sub.5.1Mo.sub.14.04C.sub.14.1B.sub.4Si.sub.1.96Cu.sub.0.36 and Co.sub.61.4Ni.sub.5.2Mo.sub.14.33C.sub.14.3B.sub.3Si.sub.1.7Cu.sub.0.07. The results for the elastic reduced modulus E.sub.r and the deformation energies with respect to the applied load P are listed in Table 5. As shown in
(42) The results have shown that the novel amorphous alloys according to the invention are able to fulfill the three requirements of high glass forming ability, high strength and high ductility. The examples of the invention cover compositions with an alloying element X being Si, V and/or Cu. However, minor additions (≤2% atomic percent) of other elements can be considered without significantly altering the properties of the alloy. Thereby, the present invention also covers X element being selected from the group consisting of P, Y, Er (≤1% atomic percent), Ga, Ta, Nb and W. Minor additions of Fe and Cr (≤3% and preferably ≤2% atomic percent) may also be considered without significantly affecting the properties of the amorphous alloys.
(43) TABLE-US-00005 TABLE 5 P E.sub.r HV U.sub.tot U.sub.p U.sub.el Alloy (mN) (GPa) (GPa) (μJ) (μJ) (μJ) Comparative Co.sub.50Cr.sub.10Ni.sub.5Mo.sub.14C.sub.10B.sub.11 3 177.7 11.98 113.09 61.94 51.15 example Examples of Co.sub.60Ni.sub.5Mo.sub.14C.sub.16B.sub.5 3 168.2 10.67 120.54 68.41 52.12 the Invention Co.sub.60.6Ni.sub.9.15Mo.sub.10.1C.sub.14B.sub.4Si.sub.1.9Cu.sub.0.17 3 155 10.1 125.42 72.04 53.39 Co.sub.60.44Ni.sub.5.1Mo.sub.14.04C.sub.14.1B.sub.4Si.sub.1.96Cu.sub.0.36 3 159.4 10.56 122.88 70.46 52.42 Co.sub.61.4Ni.sub.5.2Mo.sub.14.33C.sub.14.3B.sub.3Si.sub.1.7Cu.sub.0.07 3 125.9 9.94 135.64 72.31 63.33