CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to, and benefits of Chinese Patent Application No. 200910110323.5 filed with State Intellectual Property Office, P. R. C. on October 22, 2009, the entire content of which is incorporated herein by reference.

FIELD

The present disclosure relates to an amorphous alloy, and a method for preparing the same, more particularly to a Zr-based amorphous alloy, and a method for preparing the same.

BACKGROUND

Amorphous alloys are a new type of long-range-disorder but short-range-order alloy materials. Due to the unique micro-structures, amorphous alloys have better mechanical, physical, and chemical performances compared with conventional crystalline metal materials.

Zr-based bulk amorphous alloys have good glass formability, mechanical properties and thermal stability, such as Zr-Al-Cu-Ni bulk alloy system, which is one of the best bulk amorphous alloy systems but requires demanding preparing conditions and raw materials with high purity. For example, the Zr-Al-Cu-Ni bulk alloy system is manufactured under the conditions of: a vacuum degree of less than about 10 ^"2 Pa, a Zr purity of greater than about 99.99 wt%, and an oxygen content of less than about 250 ppm. Therefore, the manufacturing cost is high and the alloy system may not be machined due to its high fragility, thus seriously hampering the large-scale application and industrial production of the bulk alloy system. It has been tried to incorporate metal elements including Ag, Zn, Ti, Ta, etc. to the Zr-Al-Cu-Ni bulk alloy system, to reduce the requirement of the demanding preparing conditions. However, the metal elements additives can change the glass formability, thermal stability, and crystallization behavior and performance of the original bulk alloy system.

US patent No. 6,682,611B2 discloses an amorphous alloy, in which element Y was added into the Zr-Cu-Al-Ni bulk amorphous alloy system. The additive Y may reduce the requirements for the preparing conditions to a certain extent. However, due to low impact toughness and compressive fracture strength of the amorphous alloy system, the machining performance thereof is poor, thus limiting its application as an industrial product.

Chinese patent No.CN1948543A discloses a Cu-based bulk amorphous alloy, which comprises 30 wt% to 60 wt% of Cu, 30 wt% to 60 wt% of Zr, 5 wt% to 15 wt% of Al, and 0.01 wt% to 10 wt% of rare earth element, which is selected from Sc, Y, or others. The Cu-based bulk amorphous alloy has no plastic deformability as well as poor impact toughness, and requires demanding preparing conditions and high purity raw materials, thus hampering massive production thereof. SUMMARY

In viewing thereof, the present disclosure is directed to provide a bulk amorphous alloy with enhanced processability and excellent deformability with decreased raw material purity requirement. Further, a method of preparing the same is also provided with a relatively favorable preparing condition.

According to an embodiment of the disclosure, a Zr-based amorphous alloy is provided. The

Zr-based amorphous alloy may be represented by the general formula of: (Zr _x AlyCu _z Nii- _x -y. _z )ioo-a-bSc _a Yb. x, y and z may be atomic percents, and a and b may be atom molar ratios, in which: 0.45<x<0.60, 0.08<y<0. 12, 0.25<z<0.35, 0<a<5, and 0<b<0. 1.

According to another embodiment of the invention, a method for preparing a Zr-based amorphous alloy is provided. The method may comprise the steps of: melting a raw material comprising Zr, Al, Cu, Ni, Sc, and Y to form a melted alloy; and molding the melted alloy with cooling to form the Zr-based amorphous alloy. The Zr-based amorphous alloy may be represented by the general formula of: (Zr _x AlyCu _z Nii- _x -y. _z )ioo-a-bSc _a Yb; and x, y, z are atomic percents, and a and b are atom molar ratios at ranges of: 0.45<x<0.60, 0.08<y<0.12, 0.25<z<0.35, 0<a<5, 0<b<0.1.

The addition of element Sc to the Zr-based amorphous alloy according to the present disclosure may effectively enhance flowability and slagging property of the melted alloy, and provide excellent deformability, and enhanced mold filling capability. The method for preparing the Zr-based amorphous alloy of the present disclosure may have low requirements of the raw material purity and the preparing conditions, such as vacuum degree, cooling speed, and melting and molding devices, etc. The Zr-based amorphous alloy may have excellent impact toughness and compressive fracture strength, which is suitable for machining.

Additional aspects and advantages of the embodiments of present invention will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWING

These and other aspects and advantages of the invention will become apparent and more readily appreciated from the following descriptions taken in conjunction with the drawings in which: FIG. 1 is a diagram showing X-ray diffraction patterns of exemplary alloys according to the present disclosure.

DETAILED DISCRETION OF THE EMBODIMENT

Reference will be made in detail to embodiments of the present disclosure. The embodiments described herein are explanatory, illustrative, and used to generally understand the present disclosure. The embodiments shall not be construed to limit the present disclosure. The same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the descriptions.

According to an aspect of the present disclosure, a Zr-based amorphous alloy is provided.

The Zr-based amorphous may be represented by the general formula of: (Zr _x AlyCu _z Nii- _x -y. _z )ioo-a-bSc _a Yb. x, y, and z are atomic percents, and a and b are atom molar ratios, in which: 0.45<x<0.60, 0.08<y<0.12, 0.25<z<0.35, 0<a<5, and 0<b<0.1.

In an alternative embodiment, 0.50<x<0.55, 0.08<y<0.10, 0.28<z<0.32, 0<a<3, and 0.05<b<0.1.

In a further alternative embodiment, the Zr-based amorphous alloy may be represented by the general formula of: (Zr ₀ .52Alo.ioCuo.305Nio.o75)ioo-a-bSc _a Yb.

According to another aspect of the present disclosure, a method for preparing a Zr-based amorphous is provided. The method comprises the steps of: melting a raw material comprising Zr, Al, Cu, Ni, Sc, and Y to form a melted alloy; and cooling molding the melted alloy to form the Zr-based amorphous alloy. The Zr-based amorphous alloy is represented by the general formula of: (ZrxAlyCuzNii-x-y- _z )ioo-a-bScaYb; in which x, y, and z are atomic percents, and a and b are atom molar ratios, in which: 0.45<x<0.60, 0.08<y<0.12, 0.25<z<0.35, 0<a<5, and 0<b<0.1.

According to the method of the present disclosure, impurities in the raw material less than a predetermined content may not influence the melting step. In an embodiment, the raw material may have an impurity content of less than about 5 atomic percent, based on the total weight of the Zr-based amorphous alloy. The higher the purity of the raw material, the easier the formation of the Zr-based amorphous alloy would be. In an embodiment of the present disclosure, the raw material may have a purity of about 95 wt% to about 100 wt%. According to the method of the present disclosure, small content of oxygen in the raw material may not affect the performance of the Zr-based amorphous alloy. In an embodiment, the raw material may have an oxygen content of less than about 1 atomic percent.

In an embodiment, the melting and molding steps may be performed under protective gas or vacuum, to protect the raw material from being oxidized during melting. In an embodiment, the raw material has better oxidative stability, so that the requirements for the protective gas or vacuum may be lowered. The protective gas may be selected from the group consisting of noble gases, nitrogen, and the combinations thereof, such as helium, nitrogen, argon, krypton, and the combinations thereof. The protective gas may have a purity of not less than about 94% by volume. In an embodiment of the present disclosure, the protective gas may have a purity of about 94% to about 99.9% by volume. Before blowing protective gas into a melting furnace, the melting furnace may be vacuumed to a vacuum degree of less than about 1000 Pa. In an embodiment of the present disclosure, the melting and cooling molding steps may be performed under vacuum with a vacuum degree of about 0.01 Pa to about 1000 Pa.

The melting step may be achieved by any known method in the art, provided that the raw material is melted sufficiently. In an embodiment of the present disclosure, the melting may be performed in a conventional melting device, such as an arc melting furnace or an induction melting furnace. The melting temperature and the melting time may vary according to different raw materials. In an embodiment of the present disclosure, the melting step may be performed at a temperature of about 1200°C to about 3000°C for about 0.5 minutes to about 5 minutes. In an alternative embodiment, the melting step may be performed at a temperature of about 1200°C to about 2500 °C for about 1 minute to about 3 minutes.

The Zr-based amorphous alloy of the present disclosure has strong casting ability, so that the cooling molding step is known to those skilled in the art, such as casting the melted alloy in a mould with cooling. In some embodiments of the present disclosure, the casting may be gravity casting, suction casting, spray casting or die casting. As used herein, the term "gravity casting" may refer to casting the melted alloy into a mould by gravity of the melted alloy. In an embodiment, the mould may be made from copper alloy, stainless steel, and materials having a thermal conductivity of about 30 W/(m ^» K) to about 400 W/(m ^» K) (alternatively about 50 W/(m ^« K) to about 200 W/(m ^» K)). The mould may be cooled by water, oil, or liquid nitrogen, at a cooling speed of more than about 10 K/s. In an embodiment of the present disclosure, the cooling speed may be about 10 K/s to about 10 ⁴ K s. There are no special limits on the cooling degree, provided that the Zr-based amorphous alloy may be molded accordingly.

According to an embodiment, the amount of the raw material may satisfy the requirement that: 0.45<x<0.60, 0.08<y<0.12, and 0.25<z<0.35 In this way, the articles according to embodiments of this disclosure may have better glass formability and plastic deformability, and enhanced toughness and strength, without requiring strict preparing conditions.

The present disclosure will be described in detail with reference to the following embodiments. Embodiment 1

A method for preparing a Zr-based amorphous alloy comprises the following steps.

a) A raw material comprising about 50.44 atomic percent of Zr, about 9.7 atomic percent of Al, about 29.585 atomic percent of Cu, about 7.275 atomic percent of Ni, and about 3 atomic percent of Sc, each with a purity of about 95.5 wt% was melted in an arc melting furnace available from SKY Technology Development Co., Ltd., Chinese Academy of Sciences. The furnace was vacuumed until a vacuum degree of about 5 Pa, then nitrogen with a purity of about 99.9% by volume was blowed into the melting furnace as protective gas. The raw material was melted at a temperature of about 1300°C for about 3 minutes to form a melted alloy.

b) The melted alloy was poured into a copper mould by gravity casting, and cooled by water at a cooling speed of about 10 ³ K/s to form a Zr-based amorphous alloy sample Al with a diameter of about 2 millimeters and a length of about 20 millimeters. Al was tested by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) and a composition of (Zr ₀ .52Alo.ioCuo.305Nio.o75)97Sc ₃ was obtained.

Comparative Embodiment 1

A method for preparing an amorphous alloy disclosed in US patent No. US6,682,611B2 comprises the following steps.

The method was substantially similar to that in Embodiment 1, with the exception that the raw material comprises about 53.9 atomic percent of Zr, about 14.7 atomic percent of Al, about 19.6 atomic percent of Cu, about 9.8 atomic percent of M, and about 2 atomic percent of Y. The amorphous alloy sample Dl was obtained and tested by ICP-AES elemental analysis to obtain a composition of (Zr ₀ .55Alo.i ₅ Cuo.2o io.io) 8Y2.

Comparative Embodiment 2

A method for preparing a Cu-based bulk amorphous alloy disclosed in CN patent No. CN1948543A comprises the following steps.

The method was substantially similar to that in Embodiment 1, with the exception that the raw material comprises about 30 atomic percent of Zr, about 5 atomic percent of Al, about 60 atomic percent of Cu, and about 5 atomic percent of Sc. The amorphous alloy sample D2 was obtained and characterized by elemental analysis to obtain a composition of Cu6oZr ₃₀ Al ₅ Sc5.

Embodiment 2

A method for preparing a Zr-based amorphous alloy comprises the following steps.

The method was substantially similar to that in Embodiment 1, with the exception that the raw material comprises about 51.74 atomic percent of Zr, about 9.95 atomic percent of Al, about 30.3475 atomic percent of Cu, about 7.4625 atomic percent of Ni, and about 0.5 atomic percent of Sc. The Zr-based amorphous alloy sample A2 was obtained and characterized by elemental analysis to obtain a composition of (Zro.52Alo.ioCuo.305 io.o75)99.sSco.5.

Embodiment 3

A method for preparing a Zr-based amorphous alloy comprises the following steps.

The method was substantially similar to that in Embodiment 1, with the exception that the raw material comprises about 49.4 atomic percent of Zr, about 9.5 atomic percent of Al, about 28.975 atomic percent of Cu, about 7.125 atomic percent of Ni, and about 5 atomic percent of Sc. The Zr-based amorphous alloy sample A3 was obtained and characterized by elemental analysis to obtain a composition of (Zr ₀ .52Al _0. ioCuo. ₃₀ 5 io.o75)95Sc5.

Embodiment 4

A method for preparing a Zr-based amorphous alloy comprises the following steps.

The method was substantially similar to that in Embodiment 1, with the exception that the raw material comprises about 48.5 atomic percent of Zr, about 9.7 atomic percent of Al, about 29.1 atomic percent of Cu, about 9.7 atomic percent of Ni, and about 3 atomic percent of Sc. The Zr-based amorphous alloy sample A4 was obtained and characterized by elemental analysis to obtain a composition of (Zro.5Alo _. iCuo. ₃ Nio _. i) ₉ 7Sc ₃ .

Embodiment 5

A method for preparing a Zr-based amorphous alloy comprises the following steps.

The method was substantially similar to that in Embodiment 1, with the exception that the raw material comprises about 43.6275 atomic percent of Zr, about 9.695 atomic percent of Al, about 33.9325 atomic percent of Cu, about 9.695 atomic percent of Ni, about 3 atomic percent of Sc, and about 0.05 atomic percent of Y. The Zr-based amorphous alloy sample A5 was obtained and characterized by elemental analysis to obtain a composition of

(Zro.45Alo.lCuo.35Nio.l)96.95SC3Yo.05.

Embodiment 6

A method for preparing a Zr-based amorphous alloy comprises the following steps.

The method was substantially similar to that in Embodiment 1, with the exception that the raw material comprises about 50.3932 atomic percent of Zr, about 9.691 atomic percent of Al, about 29.55755 atomic percent of Cu, about 7.26825 atomic percent of Ni, about 3 atomic percent of Sc, and about 0.09 atomic percent of Y. The Zr-based amorphous alloy sample A6 was obtained and characterized by elemental analysis to obtain a composition of

(Zro.52 lo.loCUo.305Nio.075) 6.9l SC3Yo.0 - Embodiment 7

A method for preparing a Zr-based amorphous alloy comprises the following steps.

The method was substantially similar to that in Embodiment 1, with the exception that the arc melting furnace was vacuumed with a vacuum degree of about 10 Pa, and melting was performed at a temperature of about 1500°C for about 2.5 minutes, and the cooling speed during cooling molding was about 2>< 10 ³ K/s. The Zr-based amorphous alloy sample A7 was obtained and characterized by elemental analysis to obtain a composition of (Zr ₀ .52Alo _. ioCuo.305Nio.o75)97Sc3.

Test

1) XRD (X- ay Diffraction)

Zr-based alloy samples Al-7 and alloy samples Dl-2 were tested by D-MAX2200PC X-ray powder diffractometer under conditions of: a copper target, an incident wavelength of about 1.54060 A, an accelerating voltage of about 40 KV, a current of about 20 mA, a scanning step of about 0.04° respectively. The testing results are shown in Fig. 1. From Fig. l, it can be concluded that the Zr-based alloys Al-7 are all amorphous.

2) Impact Toughness

This test was performed on ZBC1000 pendulum impact tester available from Shenzhen sans Materials Testing Co., Ltd., PR C. Each of Zr-based alloy samples Al-7 and alloy samples Dl-2 was cut to obtain a U-shape gap with a length of about 2 mm, then tested by Charpy Pendulum Impact Test Method according to GBT 229-2007 to obtain the impact toughness. The results were shown in Table 1.

3) Compressive Fracture Strength and Stress-Strain Curve

Each of Zr-based alloy samples Al-7 and alloy samples Dl-2 was cut into an alloy bar with a diameter of about 1 millimeter and a length of about 2 millimeters. The ally bars were tested by a CMT5105 Electronic Universal Testing Machine to obtain compressive fracture strengths and stress-strain curves of the samples respectively. Maximum plastic strains (ε _ρ ) were calculated from the respective stress-strain curves. The results were shown in Table 1. Table 1

As shown in Table 1, the impact toughness and compressive fracture strengths of the Zr-based amorphous alloy samples according to embodiments of the present disclosure are all higher than those of the amorphous alloy samples in the prior art, without requiring demanding preparing conditions. As to the plastic deformation capability, each of the Zr-based amorphous alloy samples according to embodiments of the present disclosure has a maximum plastic strain of more than about 11%, while alloy sample D l has a very small maximum plastic strain of about 1.5 % and D2 has no plastic deformation capability.

Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that changes, alternatives, and modifications all falling into the scope of the claims and their equivalents can be made in the embodiments without departing from spirit and principles of the invention.