阅读说明：本技术 一种无Co共晶中熵合金及其制备方法 (Co-free eutectic medium-entropy alloy and preparation method thereof ) 是由 于鹏飞 卢烨 李工 刘日平 于 2020-07-31 设计创作，主要内容包括：本发明公开一种无Co共晶中熵合金及其制备的方法,属于共晶高熵合金制备技术领域,本发明合金的化学成分表达式为CrFeNiNb<Sub>x</Sub>,x取值范围为0.25～0.33；其中,CrFeNiNb<Sub>0.25</Sub>合金的组织为亚共晶组织,CrFeNiNb<Sub>0.31</Sub>合金的组织为共晶组织,CrFeNiNb<Sub>0.33</Sub>合金的组织为过共晶组织。利用真空电弧熔炼技术对预先设计好成分的中熵合金CrFeNiNb<Sub>x</Sub>进行制备。合金微观结构由FCC和Laves两相组成,通过Nb的添加,合金强度相比单相FCC结构中熵合金有很大提高,完全共晶成分的CrFeNiNb<Sub>0.31</Sub>合金具有优异的综合力学性能。并且,由于不含有贵金属Co,使得该共晶中熵合金具有潜在的工程应用价值。(The invention discloses a Co-free eutectic medium-entropy alloy and a preparation method thereof, belonging to the technical field of preparation of eutectic high-entropy alloys x The value range of x is 0.25-0.33; wherein, CrFeNiNb 0.25 The structure of the alloy is hypoeutectic structure, CrFeNiNb 0.31 The structure of the alloy is eutectic structure, CrFeNiNb 0.33 The structure of the alloy is a hypereutectic structure. The medium entropy alloy CrFeNiNb with the pre-designed components is processed by utilizing the vacuum arc melting technology x The preparation is carried out. The alloy microstructure consists of FCC and Laves phases, the alloy strength is greatly improved compared with the entropy alloy in a single-phase FCC structure by adding Nb, and the CrFeNiNb with completely eutectic components 0.31 The alloy has excellent comprehensive mechanical properties. In addition, the eutectic medium entropy alloy has potential engineering application value because the eutectic medium entropy alloy does not contain noble metal Co.)

1. A Co-free eutectic medium entropy alloy, the composition of which comprises: cr, Fe, Ni and Nb; the molar ratio of Cr, Fe, Ni and Nb is 1:1:1: x, wherein x is atomic number percentage, and x is 0.25-0.33; the alloy microstructure consists of two phases of FCC and Laves, and is a eutectic structure containing FCC/Laves phases.

2. The Co-free eutectic medium entropy alloy of claim 1, wherein when x is 0.31, the alloy is formed by alternately arranging FCC phase and Laves phase in parallel with each other to form a finely coupled lamellar full eutectic structure.

3. A method of making a Co-free eutectic medium entropy alloy as claimed in claim 1, the method comprising:

calculating the mass of each metal simple substance and weighing high-purity Cr, Fe, Ni and Nb metal simple substances according to the molar ratio of 1:1:1: x, wherein x is the atomic number percentage, and x is 0.25-0.33;

step (2), sequentially placing the Cr, Fe, Ni and Nb metal simple substances prepared in the step (1) into a copper crucible in a smelting furnace according to the sequence of melting points from low to high;

and (3) vacuumizing the smelting furnace, filling high-purity inert protective gas, removing residual oxygen, electrifying for repeated smelting, and cooling in a water-cooled copper mold to obtain the alloy button ingot.

4. The preparation method according to claim 3, wherein in the step (1), the purity of each of the elementary metals Cr, Fe, Ni and Nb is not less than 99.95%.

5. The production method according to claim 3, wherein in the step (3), the shielding gas is argon gas, and a degree of vacuum in the melting furnace is 5 x 10^-3And when Pa, the protective gas is filled.

6. The production method according to claim 3, wherein in the step (3), pure titanium ingot is electroformed for removing residual oxygen before the electroformed elemental metal is electroformed.

7. The production method according to claim 3, wherein in the step (3), the number of times of the repeated melting is 5, and the time for each melting is 3 minutes.

Technical Field

The invention relates to the technical field of metal materials and preparation thereof, in particular to Co-free eutectic medium-entropy alloy and a preparation method thereof.

Background

The high-entropy alloy is a novel alloy developed in recent years, and mainly comprises a solid solution alloy consisting of face-centered cubic, body-centered cubic and close-packed hexagonal. The phase structure composition is simple, and the material has excellent mechanical property, and is expected to become a new generation of structural material.

The eutectic high-entropy alloy has been widely applied to the field of traditional metals due to the advantages of low melting point, good casting performance, controllable structure and the like. In 2014, a Lu-Flat learner of the university of the great connecting engineering provided the concept of eutectic high-entropy alloy, and AlCoCrFeNi designed by the concept_2.1The eutectic high-entropy alloy consists of a soft FCC phase and a hard BCC phase, and has good casting performance and excellent mechanical property. At present, a large number of CoCrFeNi-based and CoCrNi-based eutectic high entropy alloys have been reported. Jiang et al reported CoCrFeNiTa_0.4The eutectic alloy consists of a tough FCC phase and a brittle and hard Laves phase, the breaking strength of the eutectic alloy reaches 2293MPa, and the compression plasticity of the eutectic alloy is 22.6 percent. Chanda et al developed CoCrFeNiNb_0.45A fully eutectic high entropy alloy. Patent 2018109454652 discloses a high entropy eutectic alloy of Ni-Co-Cr-Ti-Ta-Al-M with chemical composition expression of Ni_aCo_bCr_cTi_dTa_eAl_fM_gAnd M is one or two of Hf and Zr. Patent 2018108407654 discloses a Co-Fe-Ni-V-Zr high entropy alloy with a composition, in terms of mole ratios, of CoFeNi_xVZr_0.55Wherein the content of Ni is more than or equal to 1.8 and less than or equal to 2.6 according to the molar ratio of x. Patent CN201911156093.6 discloses a CoCrNiHf_xThe eutectic medium-entropy alloy has excellent medium-high temperature comprehensive mechanical properties, wherein x is 0.1-0.5.

The eutectic high-entropy alloy mainly comprises an FCC phase and a BCC phase or an FCC plus Laves phase from the perspective of alloy phase composition. From the aspect of alloy composition, the eutectic structure is obtained by mainly taking Ni, Co, Fe, Cr and Al as the basis and adjusting Zr, Ti, Hf, V, Nb, Ta, Mo and other elements. As the used Co simple substance is expensive and the price of the Co simple substance is more than six times higher than that of Cr, Fe, Ni and the like, the manufacturing cost of the eutectic high-entropy alloy is higher, and the industrial application of the eutectic high-entropy alloy is hindered.

Therefore, under the condition of ensuring the mechanical property of the eutectic high-entropy alloy, the content of the Co element in the eutectic high-entropy alloy is reduced so as to reduce the manufacturing cost of the alloy, and further promote the engineering application of the eutectic high-entropy alloy, which is a technical problem to be solved urgently at present.

Disclosure of Invention

In order to solve the technical problem that the Co-containing eutectic high-entropy alloy is high in cost, the invention aims to provide the Co-free eutectic medium-entropy alloy and the preparation method thereof.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

the invention provides a Co-free eutectic medium entropy alloy, which comprises the following components: cr, Fe, Ni and Nb; the molar ratio of Cr, Fe, Ni and Nb is 1:1:1: x, wherein x is atomic number percentage, and x is 0.25-0.33; the chemical composition expression is CrFeNiNb_x(ii) a The alloy microstructure is composed of two phases of FCC and Laves, and is a eutectic structure containing FCC/Laves phases.

Preferably, when x is 0.31, the alloy is formed by alternately arranging FCC phase and Laves phase in parallel to form a finely coupled lamellar fully eutectic structure.

On the other hand, the invention also provides a preparation method of the Co-free eutectic medium entropy alloy, which comprises the following steps:

calculating the mass of each metal simple substance and weighing high-purity Cr, Fe, Ni and Nb metal simple substances according to the molar ratio of 1:1:1: x, wherein x is the atomic number percentage, and x is 0.25-0.33;

step (2), sequentially placing the Cr, Fe, Ni and Nb metal simple substances prepared in the step (1) into a copper crucible in a smelting furnace according to the sequence of melting points from low to high;

and (3) vacuumizing the smelting furnace, filling high-purity inert protective gas, removing residual oxygen, electrifying for repeated smelting, and cooling in a water-cooled copper mold to obtain the alloy button ingot.

Preferably, in the step (1), the purity of each metal elementary substance Cr, Fe, Ni and Nb raw material is more than or equal to 99.95%.

Preferably, in the step (2), the shielding gas is argon, and the vacuum degree in the smelting furnace is 5 × 10^-3And when Pa, the protective gas is filled.

Preferably, in the step (2), pure titanium ingots are electrified and smelted before the elemental metal is electrified and smelted, so that residual oxygen is removed.

Preferably, in the step (2), the number of times of melting is repeated is 5 times, and the time for each melting is 3 minutes.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention provides a Co-free eutectic medium-entropy alloy, which does not contain expensive metal Co in the components, so that the preparation cost of the alloy is greatly reduced.

2. When x is 0.31, the Co-free eutectic medium-entropy alloy provided by the invention can obtain CrFeNiNb with excellent mechanical property_0.31The alloy disclosed by the invention has the advantages that the combination of high strength and high plasticity is realized by fully eutectic alloy, and the plastic strain can reach 30% under the conditions that the yield strength is 1368MPa and the fracture strength is 2414 MPa. And the alloy has better fluidity and casting performance, and solves the problem of poor casting performance of the single-phase high-entropy alloy.

3. The Co-free eutectic medium-entropy alloy provided by the invention has excellent mechanical properties, and the ingot obtained by smelting does not need any heat treatment process or deformation strengthening process, so that the strength is higher, and the room-temperature plasticity is good.

Based on the reasons, the invention has engineering application value and can be widely popularized in the fields of metal materials and preparation thereof.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 shows CrFeNiNb in example 1 of the present invention_0.25XRD pattern of the cast ingot;

FIG. 2 shows CrFeNiNb in example 1 of the present invention_0.25SEM image of ingot;

FIG. 3 shows CrFeNiNb in example 1 of the present invention_0.25Room temperature compression curve of the ingot;

FIG. 4 shows CrFeNiNb in example 2 of the present invention_0.31XRD pattern of the cast ingot;

FIG. 5 shows CrFeNiNb in example 2 of the present invention_0.31SEM image of ingot;

FIG. 6 shows CrFeNiNb in example 2 of the present invention_0.31Room temperature compression curve of the ingot;

FIG. 7 shows CrFeNiNb in example 3 of the present invention_0.33XRD pattern of the cast ingot;

FIG. 8 shows CrFeNiNb in example 3 of the present invention_0.33SEM image of ingot;

FIG. 9 shows CrFeNiNb in example 3 of the present invention_0.33Room temperature compression curve of ingot.

Detailed Description

In order to more clearly illustrate the technical solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the specification, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

The invention aims to provide a Co-free eutectic medium-entropy alloy, which is characterized in that a eutectic structure of an FCC phase and a Laves phase is formed in the alloy by adding a metal element Nb to CrFeNi medium-entropy alloy with a single-phase FCC structure, the alloy has mechanical properties similar to those of Co-containing eutectic high-entropy alloy, and the preparation cost is lower due to the fact that Co element is not contained, so that a solution is provided for developing low-cost eutectic high-entropy alloy with engineering application potential.

The invention provides a Co-free eutectic medium entropy alloy, which comprises the following components: cr, Fe, Ni and Nb; the molar ratio of Cr, Fe, Ni and Nb is 1:1:1: x, wherein x is atomic number percentage, and x is 0.25-0.33; the alloy microstructure consists of two phases of FCC and Laves, and is a eutectic structure containing FCC/Laves phases. The chemical composition expression of the alloy is CrFeNiNb_xThe value range of x is 0.25-0.33; wherein, CrFeNiNb_0.25The structure of the alloy is hypoeutectic structure, CrFeNiNb_0.31The structure of the alloy is eutectic structure, CrFeNiNb_0.33The structure of the alloy is a hypereutectic structure.

The invention also provides a preparation method of the alloy, which is to use the vacuum arc melting technology to pre-design the medium entropy alloy CrFeNiNb with the components_xThe preparation method comprises the following steps:

and (1) calculating the mass of each metal simple substance and weighing high-purity Cr, Fe, Ni and Nb metal simple substances according to the molar ratio of 1:1:1: x, wherein x is the atomic number percentage, and x is 0.25-0.33.

Wherein, preferably, the purity of each metal elementary substance Cr, Fe, Ni and Nb raw material is more than or equal to 99.95 percent;

and (2) sequentially placing the Cr, Fe, Ni and Nb metal simple substances prepared in the step (1) into a copper crucible in a smelting furnace according to the sequence of melting points from low to high.

And (3) vacuumizing the smelting furnace, filling high-purity inert protective gas, removing residual oxygen, electrifying for repeated smelting, and cooling in a water-cooled copper mold to obtain the alloy button ingot.

Wherein, the protective gas is preferably argon, and the vacuum degree in the smelting furnace is 5 multiplied by 10^-3And when Pa, protective gas is filled. Preferably, pure titanium ingots are electrified and smelted before the elemental metal is electrified and smelted, and the pure titanium ingots are used for removing residual oxygen. Preferably, the melting is repeatedThe smelting times are 5 times, and the time of each smelting is 3 min.

The technical solution of the present invention is further described in detail with reference to the specific examples below.