A method for designing eutectic multi-principal element alloys based on binary phase diagrams and natural mixing criterion

Abstract

The application provides a eutectic multi-component alloy design method based on a binary phase diagram and a natural mixing criterion, and belongs to the technical and preparation fields of alloy materials. The method is as follows: firstly, a eutectic point of base elements and added elements is determined through an alloy phase diagram. The eutectic composition point is proportioned, a cast state organization after arc melting is cut, EDS analysis is carried out, the composition of different eutectic regions is weighted and averaged, and the element content of the eutectic region, that is, the element content of the eutectic multi-component alloy in the cast state, is obtained. The application overcomes the difficulty of finding the eutectic point in the multi-component phase diagram, and secondly, the eutectic point of the multi-component alloy does not need to be determined by the calculation simulation of the thermodynamic data software and the trial-and-error method for multiple times; by introducing the mathematical weighted average method, the experimental errors caused by the defects of the selected region organization, element segregation and the like can be effectively eliminated, and the performance in the cast state can be further improved.

Description

Technical Field

[0001] This invention provides a method for designing eutectic multi-principal alloys based on binary phase diagrams and natural mixing principles, belonging to the field of alloy materials technology and preparation. Background Technology

[0002] Eutectic alloys have a lower melting point than pure components, and their good fluidity reduces the formation of dendrites during solidification, greatly reducing defects (internal shrinkage cavities and component segregation) during casting. Furthermore, the microstructure of eutectic alloys has a certain regular shape (layered and short rod-like), which greatly improves the mechanical properties of the alloy.

[0003] Multi-principal element alloys are a hot research area in high-performance metallic structural materials. Multi-principal element alloys generally refer to alloys composed of three or more metallic elements in equal or near-equal atomic ratios. They possess many excellent properties such as high hardness and corrosion resistance. Multi-principal element eutectic alloys exhibit superior mechanical properties compared to traditional single-principal element eutectic alloys; however, due to the lack of ternary or higher multi-principal element phase diagrams, it is currently impossible to directly determine the composition ratios using phase diagrams.

[0004] Among multi-principal element alloys, there exists a class of eutectic multi-principal element alloys composed of a solid solution phase and an intermetallic compound phase. These eutectic multi-principal element alloys exhibit the following characteristics: One phase contains elements with similar atomic radii, chemical reactivity, and a small enthalpy of mixing (close to 0), thus exhibiting a weaker tendency to form compounds and readily forming a stable solid solution phase; conversely, the other phase contains elements with a large negative enthalpy of mixing and a large difference in atomic radii, making it easier to form another stable phase. Eutectic high-entropy alloys also necessarily depend on eutectic reactions between elements.

[0005] In existing technologies, finding eutectic points in multi-component phase diagrams presents challenges. Summary of the Invention

[0006] This invention addresses the problem of determining the eutectic composition of ternary or multi-component systems in the prior art by providing a method for determining the eutectic point composition of multi-component alloys based on the characteristics of binary phase diagrams and the natural mixing criterion. The method of this invention can obtain the composition of the eutectic alloy through two experiments using the proportional mixing method, and can accurately determine the composition of eutectic multi-principal element alloys without thermodynamic simulation and multiple trial and error.

[0007] Eutectic multi-principal element alloys can be viewed as pseudo-binary eutectics of type AB, where the elements in phase A have similar atomic radii and smaller enthalpies of mixing, tending to form continuous solid solutions; while the elements in phase B have more negative enthalpies of mixing than those in phase A. Therefore, by batching the elements in phase A and phase B according to the eutectic (eutectoid) points of the binary phase diagram and then mixing them in proportion, the initial eutectic multi-principal element alloy composition can be obtained.

[0008] A design method for eutectic multi-principal element alloys based on binary phase diagrams and natural mixing principles, comprising the following specific steps:

[0009] Step (1): According to the phase diagram, the matrix elements and additives are proportioned according to the eutectic point.

[0010] Step (2): The alloy batch obtained in step (1) is subjected to electric arc melting to obtain the initial alloy structure;

[0011] Step (3) The alloy obtained in step (2) is pretreated and EDS area spot scan analysis is performed in different eutectic regions. The electron beam scans the selected sample surface and the elements on the sample surface are displayed on the screen by brightness or color. The higher the brightness, the more content. The atomic ratio of the elements is obtained according to the area of ​​each element distribution relative to the total area, which is the result of EDS area spot scan analysis.

[0012] Step (4): Based on the composition results of the EDS region spot scan in step (3), perform a weighted average, that is, add up the results of each region spot scan for each element and divide by the number of times they are added to obtain the new atomic ratio of each element, which is the new alloy composition.

[0013] Step (5): According to step (4), the new ingredients are batched and smelted to obtain the final ingredients.

[0014] Furthermore, the melting current is 180A, and the melting is repeated 5-6 times.

[0015] Furthermore, the protective atmosphere during smelting is high-purity argon.

[0016] Furthermore, a Ni-Co-Al ternary principal component system is adopted.

[0017] Furthermore, in step (3), when selecting the eutectic, it is necessary to avoid areas with defects, shrinkage cavities, etc., to avoid inaccuracy of EDS area spot scanning.

[0018] Furthermore, the pretreatment process involves cutting a 2mm thick sheet using an electrical discharge wire cutter, then grinding it with sandpaper of different precision from 320 grit to 2500 grit, and polishing it with polishing liquid of different particle sizes from 3μm to 0.5μm.

[0019] Furthermore, EDS region spot scans were performed in five different eutectic regions, and the compositions were denoted as follows:

[0020] Ni a1 Co b1 Al C1 Ni a2 Co b2 Al c2Ni a3 Co b3 Al c3 Ni a4 Co b4 Alc4,Ni a5 Co b5 Al c5 .

[0021] Furthermore, the component obtained after weighted averaging is denoted as Ni. a Co b Al c , a = (a1 + a2 + a3 + a4 + a5) / 5.

[0022] Furthermore, the component obtained after weighted averaging is denoted as Ni. a Co b Al c b = (b1 + b2 + b3 + b4 + b5) / 5.

[0023] Furthermore, the component obtained after weighted averaging is denoted as Ni. a Co b Al c c = (c1 + c2 + c3 + c4 + c5) / 5.

[0024] EDS multiple regional point scans and weighted averaging: First, it can eliminate some human errors, such as defects or shrinkage cavities in the selected eutectic region. The weighted averaging method can remove some outliers. Second, compared with a single regional point scan, multiple regional point scans and weighted averaging can verify the superiority of using binary phase diagrams and the natural mixing rule. Third, the average value of multiple regional point scans can test the stability of the element distribution in the eutectic region. That is, if the results of each regional point scan are not much different, the thermal stability of the element distribution is high. If the results of each regional point scan are too different, the stability of the element distribution is not high or the eutectic region contains different dual phases.

[0025] This invention has significant advantages over existing technologies:

[0026] (1) The present invention can first determine the initial eutectic multi-principal element alloy composition by using a simple binary phase diagram and natural mixing criterion;

[0027] (2) The present invention can determine the final eutectic multi-principal element alloy composition through two experiments;

[0028] (3) This invention introduces a mathematical weighted average statistical method for the first time, which greatly reduces the impact of structural defects and element segregation caused by as-cast structures on the accuracy of experiments.

[0029] (4) The present invention uses a weighted average statistical method to determine that the mechanical properties (plasticity, yield strength, fracture strength) of the alloy are all superior to the initial alloy properties.

[0030] (5) This invention does not require thermodynamic calculation simulation and multiple trial and error to determine the final composition, which greatly shortens the experimental process and is of great significance to the research field of multi-principal element alloys. Attached Figure Description

[0031] Figure 1 SEM image of the initial eutectic multi-principal element alloy.

[0032] Figure 2 SEM image of the final eutectic high-entropy multi-principal element alloy.

[0033] Table 1 shows the EDS composition of the initial and final alloys; Table 2 shows the mechanical properties. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0035] Example 1:

[0036] A design method for eutectic multi-principal element alloys based on binary phase diagrams and natural mixing criteria, the specific steps of which are as follows:

[0037] High-purity Ni, high-purity Co, and high-purity Al were mixed in equal proportions according to the Ni-Al and Co-Al eutectic points in the binary phase diagram, with (1 / 2)Co 73.1 Al 26.9 +(1 / 2)Ni 75 Al 25 ≈(CoNi) 74 Al 26 The initial alloy (CoNi) 74 Al 26 Place it in an electric arc melting process and melt it in a protective atmosphere (argon atmosphere) with a melting current of 180A. Repeat the melting process 5-6 times, and slowly cool the current each time until the melting is complete.

[0038] The resulting initial eutectic multi-principal element alloy (CoNi) 74 Al 26 Thin slices of 2 mm thickness were cut using an electrical discharge wire cutter, then polished with sandpaper of varying fineness from 320 grit to 2500 grit, and further polished with polishing slurries of varying particle sizes from 3 μm to 0.5 μm. The polished microstructures were then analyzed using energy dispersive spectroscopy (EDS) in different regions (five times in this experiment) to obtain five sets of alloy compositions, namely Ni... a1 Co b1 Al C1 Nia2 Co b2 Al c2 ,Nia3Co b3 Alc3,Ni a4 Co b4 Al c4 Ni a5 Co b5 Al c5 Ni 36.4 Co 40.5 Al 23.1 Ni 36.4 Co 40.4 Al 23.2 Ni 36.3 Co 40.5 Al 23.2 Ni 36.6 Co 40.7 Al 22.7 Ni 36.4 Co 40.5 Al 23.1 The elemental content in different regions was then weighted and averaged to obtain the final alloy composition Ni. a Co b Al c That is Ni 36.4 Co 40.5 Al 23.1 The as-cast Ni alloy after spot scanning of the mechanical property testing area. 36.4 Co 40.5 Al 23.1 The yield strength reaches 450 MPa, compared to the original cast alloy (NiCo). 74 Al 26 The yield strength of the as-cast Ni alloy increased by 35% to 350 MPa. 36.4 Co 40.5 Al 23.1 The tensile strength reaches 1050 MPa, compared to the original cast alloy (NiCo). 74 Al 26 The tensile strength increased by 20% to 850 MPa; the original cast alloy (NiCo) 74 Al 26 The elongation after fracture is 18%, and the as-cast Ni alloy 36.4 Co 40.5 Al 23.1 While maintaining high strength, the elongation after fracture is also increased to 20%. Furthermore, the as-cast Ni alloy... 36.4 Co 40.5 Al 23.1 Its cold-rolling properties are also superior to those of the original cast alloy (NiCo). 74 Al 26The original cast alloy (NiCo) 74 Al 26 Cracks appeared when the rolling amount was 25%, while the as-cast Ni alloy... 36.4 Co 40.5 Al 23.1 Cracks did not appear until the rolling amount reached 45%.

[0039] Table 1

[0040] Ni Co Al a1 36.4 b1 40.5 c1 23.1 a2 36.4 b2 40.4 c2 23.2 a3 36.3 b3 40.5 c3 23.2 a4 36.6 b4 40.7 c4 22.7 a5 36.4 b5 40.5 c5 23.1 a 36.4 b 40.5 c 23.1

[0041] Table 2

[0042]

Claims

1. A method for designing eutectic multi-principal element alloys based on binary phase diagrams and natural mixing principles, characterized in that, The specific steps include: According to the phase diagram, the matrix elements and additives are proportioned in equal proportions according to the eutectic point; The initial alloy structure is obtained by arc melting based on the alloy batch obtained in step (1); The alloy obtained in step (2) is pretreated and EDS area spot scan analysis is performed in different eutectic regions. The electron beam scans the selected sample surface and the elements on the sample surface are displayed on the screen by brightness or color. The higher the brightness, the more content. The atomic ratio of the elements is obtained according to the area of ​​each element distribution relative to the total area, which is the result of EDS area spot scan analysis. According to the composition results of the EDS region spot scan in step (3), the weighted average is calculated, that is, the results of each region spot scan for each element are added together and then divided by the number of times they are added to obtain the new atomic ratio of each element, which is the new alloy composition. According to step (4), the new ingredients are batched and smelted to obtain the final ingredients; A Ni-Co-Al ternary principal component system was adopted.

2. The eutectic multi-principal element alloy design method based on binary phase diagrams and natural mixing criteria according to claim 1, characterized in that, The melting current is 180A, and the melting is repeated 5-6 times.

3. The eutectic multi-principal element alloy design method based on binary phase diagrams and natural mixing criteria according to claim 1, characterized in that, The protective atmosphere during smelting is high-purity argon.

4. The eutectic multi-principal element alloy design method based on binary phase diagrams and natural mixing criteria according to claim 1, characterized in that, In step (3), when selecting the eutectic, it is necessary to avoid defects and shrinkage areas to prevent inaccuracy of EDS area spot scanning.

5. The eutectic multi-principal element alloy design method based on binary phase diagrams and natural mixing criteria according to claim 1, characterized in that, The pretreatment process involves cutting a 2mm thick sheet using an electrical discharge wire cutter, then grinding it with sandpaper of different precision from 320 grit to 2500 grit, and polishing it with polishing liquid of different grit sizes from 3μm to 0.5μm.

6. The eutectic multi-principal element alloy design method based on binary phase diagrams and natural mixing criteria according to claim 1, characterized in that, The composition of Ni was determined by EDS regional spot scanning in five different eutectic regions. a1 Co b1 Al C1 Ni a2 Co b2 Al c2 Ni a3 Co b3 Al c3 Ni a4 Co b4 Alc4,Ni a5 Co b5 Al c5 .

7. The eutectic multi-principal element alloy design method based on binary phase diagrams and natural mixing criteria according to claim 1, characterized in that, The component obtained after weighted averaging is denoted as Ni. a Co b Al c , a=(a1+a2+a3+a4+a5) / 5.

8. The eutectic multi-principal element alloy design method based on binary phase diagrams and natural mixing criteria according to claim 1, characterized in that, The component obtained after weighted averaging is denoted as Ni. a Co b Al c b = (b1 + b2 + b3 + b4 + b5) / 5.

9. The eutectic multi-principal element alloy design method based on binary phase diagrams and natural mixing criteria according to claim 1, characterized in that, The component obtained after weighted averaging is denoted as Ni. a Co b Al c c = (c1 + c2 + c3 + c4 + c5) / 5.

Images