CoCrNiSi medium-entropy alloy and preparation method thereof
阅读说明：本技术 一种CoCrNiSi中熵合金及其制备方法 (CoCrNiSi medium-entropy alloy and preparation method thereof ) 是由 刘日平 逯昊燃 张星 石鹤洋 冉雨畅 张新宇 马明臻 于 2020-09-10 设计创作，主要内容包括：本发明提供了一种CoCrNiSi中熵合金及其制备方法,属于新材料制备领域。本发明提供的CoCrNiSi中熵合金中Co、Cr、Ni、Si元素的物质的量之比为Co：Cr：Ni：Si＝(0.5～1.5)：(0.5～1.5)：(0.5～1.5)：(0.35～0.55)。本发明是以CoCrNi合金体系为基体,通过添加非金属元素Si实现CoCrNi合金体系的析出强化,制备出具有高强度的CoCrNiSi中熵合金。实施例的结果显示,本发明提供的CoCrNiSi中熵合金的屈服强度可达到610～720MPa。(The invention provides a CoCrNiSi medium-entropy alloy and a preparation method thereof, belonging to the field of preparation of new materials. The ratio of the amounts of Co, Cr, Ni and Si elements in the entropy alloy of CoCrNiSi provided by the invention is Co: cr: ni: si ═ 0.5 to 1.5: (0.5-1.5): (0.5-1.5): (0.35-0.55). The invention takes a CoCrNi alloy system as a matrix, realizes precipitation strengthening of the CoCrNi alloy system by adding a non-metallic element Si, and prepares the CoCrNiSi medium entropy alloy with high strength. The results of the embodiment show that the yield strength of the entropy alloy in the CoCrNiSi provided by the invention can reach 610-720 MPa.)
1. The CoCrNiSi medium entropy alloy comprises the following components in percentage by mass: cr: ni: si ═ 0.5 to 1.5: (0.5-1.5): (0.5-1.5): (0.35-0.55).
2. The CoCrNiSi intermediate entropy alloy of claim 1, wherein the ratio of the amounts of Co, Cr, Ni and Si elements in the CoCrNiSi intermediate entropy alloy is Co: cr: ni: si ═ 0.6 to 1.2: (0.6-1.2): (0.6-1.2): (0.38-0.55).
3. The CoCrNiSi intermediate entropy alloy of claim 2, wherein the ratio of the amounts of Co, Cr, Ni and Si elements in the CoCrNiSi intermediate entropy alloy is Co: cr: ni: si ═ 0.8 to 1.1: (0.8-1.1): (0.8-1.1): (0.4-0.55).
4. The CoCrNiSi medium entropy alloy of claim 3, wherein the ratio of the amounts of Co, Cr, Ni and Si elements in the CoCrNiSi medium entropy alloy is Co: cr: ni: si ═ 0.9 to 1: (0.9-1): (0.9-1): (0.48-0.55).
5. The method for preparing the CoCrNiSi medium entropy alloy of any one of claims 1 to 4, comprising the following steps:
(1) smelting the alloy raw material, and cooling to obtain an ingot;
(2) and (2) carrying out homogenization annealing on the ingot obtained in the step (1) to obtain the CoCrNiSi medium entropy alloy.
6. The method for preparing the CoCrNiSi medium-entropy alloy according to claim 5, wherein the alloy raw material is pretreated before smelting.
7. The method for preparing the CoCrNiSi medium-entropy alloy according to claim 5, wherein the smelting temperature in the step (1) is 800-2000 ℃, and the smelting time is 30-60 min.
8. The method for preparing the CoCrNiSi medium-entropy alloy according to claim 5, wherein the cooling mode in the step (1) is furnace cooling to room temperature.
9. The method for preparing the CoCrNiSi medium-entropy alloy according to claim 5, wherein the temperature rise rate of the homogenization annealing in the step (2) is 7-15 ℃/min.
10. The method for preparing the CoCrNiSi intermediate entropy alloy according to claim 5, wherein the heat preservation temperature of the homogenizing annealing in the step (2) is 450-650 ℃, and the heat preservation time of the homogenizing annealing is 20-40 min.
Technical Field
The invention relates to the field of new material preparation, and particularly relates to a CoCrNiSi medium entropy alloy and a preparation method thereof.
Background
CoCrNi (atomic ratio 1:1:1) alloy with a face-centered cubic structure is applied to locomotive diesel engines, nuclear power station valves, marine diesel engines and various aircrafts due to excellent fracture toughness. However, the yield strength of the as-cast CoCrNi entropy alloy is low (about 200 MPa), and the toughness is not matched, so that the ability of resisting deformation is poor in structural application under severe use conditions, and the original structure of the device is difficult to maintain, so that the performance of the device is unstable.
Disclosure of Invention
The invention aims to provide a CoCrNiSi medium entropy alloy which has high yield strength.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a CoCrNiSi medium entropy alloy, wherein the mass ratio of Co, Cr, Ni and Si elements in the CoCrNiSi medium entropy alloy is Co: cr: ni: si ═ 0.5 to 1.5: (0.5-1.5): (0.5-1.5): (0.35-0.55).
Preferably, the ratio of the amounts of Co, Cr, Ni and Si elements in the entropy alloy of CoCrNiSi is Co: cr: ni: si ═ 0.6 to 1.2: (0.6-1.2): (0.6-1.2): (0.38-0.55).
Preferably, the ratio of the amounts of Co, Cr, Ni and Si elements in the entropy alloy of CoCrNiSi is Co: cr: ni: si ═ 0.8 to 1.1: (0.8-1.1): (0.8-1.1): (0.4-0.55).
Preferably, the ratio of the amounts of Co, Cr, Ni and Si elements in the entropy alloy of CoCrNiSi is Co: cr: ni: si ═ 0.9 to 1: (0.9-1): (0.9-1): (0.48-0.55).
The invention also provides a preparation method of the CoCrNiSi medium entropy alloy, which comprises the following steps:
(1) smelting the alloy raw material, and cooling to obtain an ingot;
(2) and (2) carrying out homogenization annealing on the ingot obtained in the step (1) to obtain the CoCrNiSi medium entropy alloy.
Preferably, the alloy feedstock is pretreated prior to smelting.
Preferably, the smelting temperature in the step (1) is 800-2000 ℃, and the smelting time is 30-60 min.
Preferably, the cooling mode in the step (1) is furnace cooling to room temperature.
Preferably, the temperature rise rate of the homogenization annealing in the step (2) is 7-15 ℃/min.
Preferably, the heat preservation temperature of the homogenizing annealing in the step (2) is 450-650 ℃, and the heat preservation time of the homogenizing annealing is 20-40 min.
The invention provides a CoCrNiSi medium entropy alloy, wherein the mass ratio of Co, Cr, Ni and Si elements in the CoCrNiSi medium entropy alloy is Co: cr: ni: si ═ 0.5 to 1.5: (0.5-1.5): (0.5-1.5): (0.35-0.55). According to the CoCrNiSi medium entropy alloy, a silicon-rich phase can be precipitated at a grain boundary in an alloy matrix of a solid solution structure by adding a certain amount of Si element and is dispersed in the CoCrNi medium entropy alloy matrix, so that the resistance of dislocation motion is increased, slippage is difficult to perform, and the strength of the CoCrNiSi medium entropy alloy is improved. The results of the embodiments show that the yield strength of the entropy alloy in CoCrNiSi provided by the invention is obviously improved compared with that of the entropy alloy in CoCrNi in a comparative proportion, and the yield strength of an actually measured sample can reach 610-720 MPa.
Drawings
FIG. 1 is an SEM image of an entropy alloy of CoCrNiSi in example 3 of the present invention.
Detailed Description
The invention provides a CoCrNiSi medium entropy alloy, wherein the mass ratio of Co, Cr, Ni and Si elements in the CoCrNiSi medium entropy alloy is Co: cr: ni: si ═ 0.5 to 1.5: (0.5-1.5): (0.5-1.5): (0.35-0.55).
In the present invention, the ratio of the amounts of Co, Cr, Ni, and Si elements in the entropy alloy of CoCrNiSi is preferably Co: cr: ni: si ═ 0.6 to 1.2: (0.6-1.2): (0.6-1.2): (0.38-0.55), more preferably Co: cr: ni: si ═ 0.8 to 1.1: (0.8-1.1): (0.8-1.1): (0.4 to 0.55), most preferably Co: cr: ni: si ═ 0.9 to 1: (0.9-1): (0.9-1): (0.48-0.55). In the invention, the Co, Cr, Ni and Si elements are proportioned to enable the entropy alloy in the CoCrNiSi to form a uniform structure and reduce component segregation. In the invention, the Si element can precipitate a silicon-rich phase which is dispersed and distributed at the grain boundary of the entropy alloy matrix in the face-centered cubic CoCrNi system, and can play a pinning effect at the grain boundary, increase the dislocation resistance and reduce the grain boundary slippage, thereby effectively improving the strength of the entropy alloy in the CoCrNiSi.
In an embodiment of the present invention, the CoCrNiSi medium entropy alloy can be specifically CoCrNiSi0.35Medium entropy alloy, CoCrNiSi0.45Medium entropy alloy, CoCrNiSi0.55And (3) medium-entropy alloy.
The CoCrNiSi medium entropy alloy provided by the invention has uniform structure and no composition segregation and casting defects, and the precipitated second phase silicon-rich particles are dispersed in the matrix, so that the crystal grains are fine and the structure is compact, and the CoCrNiSi medium entropy alloy has high yield strength.
The invention also provides a preparation method of the CoCrNiSi medium entropy alloy in the technical scheme, which comprises the following steps:
(1) smelting the alloy raw material, and cooling to obtain an ingot;
(2) and (2) carrying out homogenization annealing on the ingot obtained in the step (1) to obtain the CoCrNiSi medium entropy alloy.
The alloy raw materials are smelted and cooled to obtain the cast ingot.
In the present invention, the alloy raw materials are preferably pretreated before melting; the pretreatment preferably comprises polishing, ultrasonic cleaning and drying by a blower in sequence. The polishing is not particularly limited, and the oxide layer on the surface of the raw material can be removed. In the invention, the power of ultrasonic cleaning is preferably 340-370W, more preferably 350-360W; the time for ultrasonic cleaning is preferably 20-30 min, and more preferably 25-30 min. The drying treatment of the blower is not particularly limited, and the surface of the raw material can be completely dried. According to the invention, through pretreatment of the alloy raw material, impurity elements can be prevented from being mixed during smelting, the uniformity of the components of the alloy ingot is ensured, and the high-strength CoCrNiSi medium-entropy alloy can be obtained more favorably.
In the invention, the smelting temperature is preferably 800-2000 ℃, more preferably 900-1500 ℃, and most preferably 1000-1300 ℃; the smelting time is preferably 30-60 min, more preferably 40-60 min, and most preferably 50-60 min.
In the invention, the smelting device is preferably a vacuum non-consumable smelting furnace, the smelting environment of the vacuum non-consumable smelting furnace is preferably an argon environment, and the pressure of the argon environment is preferably-0.04 to-0.05 Pa. In the smelting process, the alloy raw materials can form fully-molten alloy liquid in a low-burning loss and high-uniformity mixing state, so that the volatilization of low-melting-point elements is reduced, the formation probability of air holes in the materials is reduced, the alloy elements are cooled and formed in a proportioning range, and the ingot casting with uniform components is obtained.
In the present invention, the cooling is preferably performed by furnace cooling to room temperature. The invention adopts the furnace cooling mode to directly cool and form the alloy liquid in the vacuum smelting furnace, thereby avoiding the oxidation of the molten alloy liquid in the casting process and reducing the formation of casting defects such as ingot inclusion, shrinkage cavity, insufficient casting and the like.
After the ingot is obtained, the ingot is subjected to homogenizing annealing to obtain the CoCrNiSi intermediate entropy alloy.
In the present invention, the device for the homogenizing annealing is not particularly limited, and a heating device known to those skilled in the art may be used. In the invention, the heating rate of the homogenizing annealing is preferably 7-15 ℃/min, more preferably 8-12 ℃/min, and most preferably 9-10 ℃/min. The heating rate of the homogenization annealing can ensure that the internal and external tissues of the ingot can reach the same heating and heat-preserving temperature in a short time, so that the condition that the external tissues of the ingot are heated for a long time and the internal tissues of the ingot are heated for a short time is avoided, and the CoCrNiSi medium entropy alloy with homogenized tissues can be obtained.
In the invention, the heat preservation temperature of the homogenizing annealing is preferably 450-650 ℃, more preferably 500-600 ℃, and most preferably 520-580 ℃; the heat preservation time of the homogenizing annealing is preferably 20-40 min, more preferably 25-35 min, and most preferably 30-35 min. In the present invention, the cooling method of the homogenization annealing is preferably furnace cooling. In the homogenizing annealing process, all alloy elements in the ingot are fully subjected to solid diffusion, so that the intragranular segregation can be eliminated, and the structure homogenization degree of the alloy is further improved; meanwhile, within the range of the heat preservation temperature and the heat preservation time of the homogenizing annealing, the precipitated second phase particles can be prevented from further growing and coarsening, and the growth of matrix grains is hindered through the action of the second phase particles, so that the effect of grain refinement is achieved, and the strength of the alloy is effectively improved.
The preparation method of the CoCrNiSi intermediate entropy alloy provided by the invention is more beneficial to the homogenization of the CoCrNiSi intermediate entropy alloy structure and the controllability of the grain size, and meanwhile, the yield strength of the CoCrNiSi intermediate entropy alloy can be obviously improved without plastic deformation, the process is simple, the cost is low, and the industrial mass production can be realized.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.