In-situ precipitation self-toughening MoCrTiAlC series refractory high entropy alloy and preparation method thereof

Abstract

The present invention discloses an in-situ precipitation self-toughening MoCrTiAlC series refractory high entropy alloy and a preparation method thereof, belonging to the technical field of high temperature materials. The alloy is composed of Mo, Cr, Ti, Al, and C, and the chemical composition expression is (MoCrTiAl 0.16 ) 100‑ x C x , wherein x=5-15, x is the atomic percentage of C. The refractory high entropy alloy prepared by the present invention has a BCC+FCC dual-phase structure, a compressive strength of 1900-2600MPa at room temperature, a compression plasticity of 8-11%, and a compressive strength of more than 300MPa at 1200°C, and can be widely used in high temperature environment fields. The present invention also discloses a preparation method of the refractory high entropy alloy, which is simple, easy to implement, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of high temperature materials, and in particular to an in-situ precipitation self-toughening MoCrTiAlC series refractory high entropy alloy and a preparation method thereof. The alloy can be widely used in the field of high temperature environment. Background Art

[0002] In recent years, the rapid development of aviation, aerospace, shipbuilding and other industries has put forward higher and higher requirements on the performance of hot end components. However, after several years of in-depth exploration, the performance of traditional high-temperature alloys has reached its limit and entered a bottleneck period. Taking Inconel718 alloy as an example, it has high strength below 600℃, but after exceeding 600℃, its strength drops sharply with the increase of temperature, which is difficult to meet the future industrial demand for the performance of hot end components. Therefore, it is urgent to develop new high-temperature alloys with better performance.

[0003] The introduction of the high entropy alloy design concept provides a new idea for breaking through the bottleneck of high-temperature alloys. Different from traditional single-principal alloys, high entropy alloys are a new type of alloys composed of 5 or more elements in equal atomic ratios or nearly equal atomic ratios. Among them, high entropy alloys composed of high melting point elements such as Ta, Nb, V, Mo, W, Cr, Hf, Zr, and Ti are called refractory high entropy alloys. Thanks to the high melting point characteristics of each component element, refractory high entropy alloys generally have high high temperature strength, excellent high temperature oxidation resistance, and excellent high temperature stability. Therefore, material scientists generally believe that refractory high entropy alloys have broad prospects in the application field of high temperature materials.

[0004] According to the research on the mechanical properties and microstructure characterization of MoCrTiAl refractory high entropy alloy by Laube et al., this alloy system has high high temperature strength (800℃, >1250MPa) and good plasticity under high temperature conditions, showing great application potential. However, the plasticity of this type of alloy at room temperature is less than 3%, which seriously limits the further application of refractory high entropy alloy materials in this system. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the existing technology, the object of the present invention is to provide an in-situ precipitation self-toughening MoCrTiAlC series refractory high entropy alloy and a preparation method thereof, aiming to solve the problem that the current MoCrTiAl refractory high entropy alloy has almost no room temperature plasticity.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A MoCrTiAlC series refractory high entropy alloy, the chemical formula of the alloy is: (MoCrTiAl 0.16 ) 100-x Cx , wherein x=5-15, x is the atomic percentage of C.

[0008] Furthermore, the MoCrTiAlC is a refractory high entropy alloy, and its as-cast microstructure is a BCC+FCC dual-phase structure.

[0009] Further, when x=5, the chemical formula of the alloy is: (MoCrTiAl 0.16 ) 95 C5; the alloy has a BCC+FCC dual-phase structure; the room temperature compressive strength of the alloy is 1914MPa, the compressive plasticity is 8.1%, and the compressive strength at a temperature of 1200°C is 332MPa.

[0010] Further, when x=10, the chemical formula of the alloy is: (MoCrTiAl 0.16 ) 90 C 10 ; The alloy has a BCC+FCC dual-phase structure; the room temperature compressive strength of the alloy is 2422MPa, the compressive plasticity is 11.4%, and the compressive strength at a temperature of 1200°C is 474MPa.

[0011] Further, when x=15, the chemical formula of the alloy is: (MoCrTiAl 0.16 ) 85 C 15 ; The alloy has a BCC+FCC dual-phase structure; the room temperature compressive strength of the alloy is 2539MPa, the compressive plasticity is 9.3%, and the compressive strength at a temperature of 1200°C is 685MPa.

[0012] The MoCrTiAlC series refractory high entropy alloy is prepared by vacuum arc melting.

[0013] The beneficial effects of the present invention are as follows:

[0014] (1) The present invention selects five elements, Mo, Cr, Ti, Al, and C, as alloy components, wherein Mo, Cr, Ti, and C are all refractory elements with high melting points, so the prepared alloy has good resistance to high temperature softening.

[0015] (2) The alloy of the present invention has a BCC+FCC dual-phase structure, wherein the FCC structural phase is a TiC ceramic phase precipitated in situ during the smelting process. Its function is to improve the strength of the alloy through precipitation strengthening on the one hand, and to effectively pin the grain boundaries on the other hand, thereby refining the grains, effectively improving the plastic deformation ability of the alloy, achieving a good strength-plasticity match, and promoting the application of such alloys in the field of high-temperature materials.

[0016] (3) The preparation method of the refractory high entropy alloy of the present invention is simple and easy to implement, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 For Example 1 (MoCrTiAl 0.16 ) 95 X-ray diffraction (XRD) pattern of C5 alloy.

[0018] Figure 2 For Example 1 (MoCrTiAl 0.16 ) 95 Scanning electron microscope backscatter diffraction (EBSD) image of C5 alloy.

[0019] Figure 3 For Example 1 (MoCrTiAl 0.16 ) 95 Room temperature compressive stress-strain curve of C5 alloy.

[0020] Figure 4 For Example 1 (MoCrTiAl 0.16 ) 95 High temperature compression stress-strain curve of C5 alloy at 1200℃.

[0021] Figure 5 For Example 2 (MoCrTiAl 0.16 ) 90 C 10 XRD patterns of the alloy.

[0022] Figure 6 For Example 2 (MoCrTiAl 0.16 ) 90 C 10 SEM EBSD image of the alloy.

[0023] Figure 7 For Example 2 (MoCrTiAl 0.16 ) 90 C 10 Room temperature compressive stress-strain curves of the alloy.

[0024] Figure 8 For Example 2 (MoCrTiAl 0.16 ) 90 C 10 High temperature compression stress-strain curve of the alloy at 1200℃.

[0025] Fig. 9 For Example 3 (MoCrTiAl 0.16 ) 85 C 15 XRD patterns of the alloy.

[0026] Fig.10For Example 3 (MoCrTiAl 0.16 ) 85 C 15 SEM EBSD image of the alloy.

[0027] Fig.11 For Example 3 (MoCrTiAl 0.16 ) 85 C 15 Room temperature compressive stress-strain curves of the alloy.

[0028] Fig.12 For Example 3 (MoCrTiAl 0.16 ) 85 C 15 High temperature compression stress-strain curve of the alloy at 1200℃. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0030] Embodiment 1:

[0031] The chemical composition expression of the refractory high entropy alloy in this embodiment is (MoCrTiAl 0.16 ) 95 C5, wherein the atomic percentages of Mo, Cr, Ti, Al, and C are 30.06%, 30.06%, 30.06%, 4.82%, and 5%, respectively.

[0032] This embodiment (MoCrTiAl 0.16 ) 95 The preparation method of C5 refractory high entropy alloy comprises the following steps:

[0033] S1; using metallurgical elements with a purity of more than 99.9wt.% as raw materials, using a file or sandpaper to remove the oxide layer on the surface of Mo, Cr, Ti, and Al, and then ultrasonically cleaning the polished raw materials in ethanol or acetone, and finally taking out the raw materials and air-drying or blowing them;

[0034] S2; Calculate the mass of Mo, Cr, Ti, Al and C required for each alloy according to the atomic ratio of the designed components, and then weigh and proportion them. The weighing should be accurate to ±0.001g for smelting and preparing the alloy; the C plate is cut into fine particles;

[0035] S3: According to the melting point of each metallurgical element in the raw material, the metal raw materials of each metallurgical element are placed in the water-cooled copper crucible of the vacuum non-consumable arc melting furnace from bottom to top, with C placed on the top, and the pressure of the sample chamber of the vacuum non-consumable arc melting furnace is pumped down to 5×10 -3Pa, and finally fill the sample chamber with high-purity argon gas with a purity of ≥99.9%;

[0036] S4: Vacuum arc melting, to ensure uniform alloy composition, the alloy raw materials are melted completely before melting. Each alloy ingot is melted at least 6 times, the melting current is 350-400A, and the melting temperature is guaranteed to be 3000-3500℃;

[0037] S5; when the sample chamber is cooled to room temperature, the smelted MoCrTiAlC refractory high entropy alloy is taken out.

[0038] The MoCrTiAl 0.16 ) 95 Microstructure characterization and mechanical properties testing of C5 refractory high entropy alloy:

[0039] (1) XRD analysis of alloy phase structure

[0040] A small square of 5 mm × 5 mm × 2 mm was cut from the alloy ingot prepared in Example 1 using an electric spark cutting machine, and then it was polished with 600#, 800#, 1000# and 2000# sandpaper in turn, cleaned with alcohol, and dried with cold air. Then, the prepared sample was analyzed for phase composition using an X-ray diffractometer, with a scanning angle 2θ ranging from 20° to 80° and a scanning speed of 2° / min.

[0041] (2) EBSD characterization of alloy structure

[0042] A small square of 5 mm × 5 mm × 3 mm was cut from the alloy ingot obtained in Example 1 using an electric spark cutting machine, and then polished with 600#, 800#, 1000# and 2000# sandpapers in turn, and the polished surface was vibrated and polished with a 0.05 μm SiO2 suspension, and finally ultrasonicated with alcohol for 5 minutes, dried and set aside. The EBSD mode was used for SEM characterization, and the sample was highly tilted during characterization so that the signal could be fully received. The experimental data obtained was analyzed and calibrated using Channel 5 software.

[0043] (3) Room temperature and high temperature compression mechanical properties test

[0044] The sample size used for mechanical properties analysis at room temperature and high temperature (1200℃) is The side of the cylinder was ground with a centerless grinder, and the cross section was polished flat with metallographic sandpaper. The room temperature and high temperature compression tests were conducted using an Instron 5982 universal testing machine and a Gleeble 3800 thermal simulation testing machine, respectively. The compression strain rate was 1×10 -3 / s, and three parallel samples were used for the test.

[0045] The above organizational structure characterization and mechanical properties test results are as follows Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown. This embodiment (MoCrTiAl 0.16 ) 95 The phase structure of C5 refractory high entropy alloy is BCC+FCC dual phase structure ( Figure 1 ). EBSD characterization results show that there are no obvious pores and impurities inside the alloy, the grain size is about 160μm, and there is a clear FCC phase distributed on the BCC matrix ( Figure 2 ). Further, the energy spectrum analysis shows that the precipitated phase is mainly composed of TiC, with a volume fraction of about 10.9%. The compression test results show that the present embodiment (MoCrTiAl 0.16 ) 95 The room temperature compressive strength of C5 refractory high entropy alloy is 1914MPa, the compressive plasticity is 8.1%, and the compressive strength is 332MPa at 1200°C, which is better than the room temperature performance of MoCrTiAl high entropy alloy (compressive strength <1750MPa, compressive plasticity <3%).

[0046] Table 1 is (MoCrTiAl 0.16 ) 95 Chemical composition of C5 refractory high entropy alloy matrix and precipitate phase (at.%)

[0047] area Mo Cr Ti Al C Overall ingredients 25.46 27.16 22.24 4.87 20.28 Matrix phase 26.34 24.45 20.65 4.41 24.16 Precipitated phase 4.27 3.64 41.50 0.43 50.16

[0048] Embodiment 2:

[0049] The chemical composition expression of the refractory high entropy alloy in this embodiment is (MoCrTiAl 0.16 ) 90 C 10 , wherein the atomic percentages of Mo, Cr, Ti, Al, and C are 28.42%, 28.42%, 28.42%, 4.74% and 10%, respectively.

[0050] This embodiment (MoCrTiAl 0.16 ) 90 C 10 The preparation method of the refractory high entropy alloy is the same as that in Example 1.

[0051] The MoCrTiAl 0.16 ) 90 C 10 The microstructure characterization and mechanical property testing methods of the refractory high entropy alloy are the same as those in Example 1. The test results are as follows: Figure 5 , Figure 6 , Figure 7 and Figure 8As shown. This embodiment (MoCrTiAl 0.16 ) 90 C 10 The phase structure of the refractory high entropy alloy is still a BCC+FCC dual-phase structure. The EBSD characterization results show that there are no obvious pores and impurities in the alloy, and the grain size is about 75μm, indicating that the increase in C content is conducive to grain refinement. In addition, a large amount of TiC phase is dispersed on the BCC matrix, with a volume fraction of about 21.2%. The compression test results show that the present embodiment (MoCrTiAl 0.16 ) 90 C 10 The room temperature compressive strength of the refractory high entropy alloy is 2422MPa, the compressive plasticity is 11.4%, and the compressive strength is 474MPa at a temperature of 1200°C, which is significantly better than the room temperature performance of MoCrTiAl high entropy alloy (compressive strength <1750MPa, compressive plasticity <3%).

[0052] Embodiment 3:

[0053] The chemical composition expression of the refractory high entropy alloy in this embodiment is (MoCrTiAl 0.16 ) 85 C 15 , wherein the atomic percentages of Mo, Cr, Ti, Al, and C are 26.84%, 26.84%, 26.84%, 4.48% and 15%, respectively.

[0054] This embodiment (MoCrTiAl 0.16 ) 85 C 15 The preparation method of the refractory high entropy alloy is the same as that in Example 1.

[0055] The MoCrTiAl 0.16 ) 85 C 15 The microstructure characterization and mechanical property testing methods of the refractory high entropy alloy are the same as those in Example 1. The test results are as follows: Fig. 9 , Fig.10 , Fig.11 and Fig.12 As shown. This embodiment (MoCrTiAl 0.16 ) 85 C 15 The phase structure of the refractory high entropy alloy is still a BCC+FCC dual-phase structure. The EBSD characterization results show that there are no obvious pores and impurities in the alloy, the grain size is about 80μm, and the volume fraction of the TiC phase on the matrix is ​​about 31.4%. The compression test results show that the present embodiment (MoCrTiAl 0.16 ) 85 C 15The room temperature compressive strength of the refractory high entropy alloy is 2539 MPa, the compressive plasticity is 9.3%, and the compressive strength is 685 MPa at a temperature of 1200°C, which is better than the room temperature performance of MoCrTiAl high entropy alloy (compressive strength <1750 MPa, compressive plasticity <3%).

[0056] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An in-situ precipitation self-toughening MoCrTiAlC refractory high entropy alloy, characterized in that: The chemical composition of the alloy is expressed as (MoCrTiAl 0.16 ) 100-x C x , where x = 5~15, x is the atomic percentage of C; The cast structure of the high entropy alloy is a BCC+FCC dual-phase structure; The high entropy alloy has a compressive strength of more than 1900 MPa and a compression plasticity of more than 8% at room temperature, and a compressive strength of more than 300 MPa at a temperature of 1200°C.

2. The MoCrTiAlC refractory high entropy alloy according to claim 1, characterized in that: When x=5, the chemical formula of the alloy is: (MoCrTiAl 0.16 ) 95 C5; the alloy has a BCC+FCC dual-phase structure; the room temperature compressive strength of the alloy is 1914 MPa, the compressive plasticity is 8.1%, and the compressive strength at 1200°C is 332 MPa.

3. The MoCrTiAlC refractory high entropy alloy according to claim 1, characterized in that: When x=10, the chemical formula of the alloy is: (MoCrTiAl0.16) 90 C 10 ; The alloy has a BCC+FCC dual-phase structure; the room temperature compressive strength of the alloy is 2422 MPa, the compressive plasticity is 11.4%, and the compressive strength is 474 MPa at a temperature of 1200°C.

4. The MoCrTiAlC refractory high entropy alloy according to claim 1, characterized in that: When x=15, the chemical formula of the alloy is: (MoCrTiAl0.16) 85 C 15 ; The alloy has a BCC+FCC dual-phase structure; the room temperature compressive strength of the alloy is 2539 MPa, the compressive plasticity is 9.3%, and the compressive strength is 685 MPa at a temperature of 1200°C.

5. A MoCrTiAlC refractory high entropy alloy as claimed in claim 1, characterized in that: The high entropy alloy is prepared by melting using a vacuum arc method.

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