Alpha2-phase reinforced refractory multi-principal-element alloy with high tensile strength and high wear resistance and preparation method of alpha2-phase reinforced refractory multi-principal-element alloy

Abstract

The invention discloses an alpha2-phase reinforced refractory multi-principal-element alloy with high tensile strength and high wear resistance. The chemical expression of the alpha2-phase reinforced refractory multi-principal-element alloy is Ti50Zr30Nb10Al10. On the basis of hot pressing and aging treatment, a hard needle-shaped (Ti, Zr) 3Al type alpha2 phase is introduced into a BCC matrix, due to the high bearing capacity and shear deformation capacity of the alpha2 phase, the yield strength and wear resistance of the alloy material are synergistically improved, then the safety and reliability of the alloy material are improved, and the alloy material is expected to be used for high-strength wear-resistant mechanical parts and has wide application prospects. And the problems of high wear rate, low strength and the like of the current refractory multi-principal element alloy can be solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of multi-principal alloys, and in particular relates to an α2 phase-reinforced refractory multi-principal alloy with high tensile strength and high wear resistance and a preparation method thereof. Background Art

[0002] Scientific research and industrial applications have always maintained their enthusiasm for the pursuit of high-strength, toughness and wear-resistant alloys. According to statistics, more than 70% of mechanical equipment damage is caused by various forms of wear. If the losses caused by material wear and failure during the operation of mechanical equipment can be reduced, the production cost can be greatly reduced, bringing considerable economic benefits to society. In recent years, lightweight refractory multi-principal alloys composed of elements such as Ti, Zr, Hf, Nb, Ta, V, and Al have attracted much attention due to their low density, high melting point and good processing capabilities, making them expected to show broad application potential in aviation, navigation, military, chemical industry, energy and other fields. However, the strength and wear resistance of lightweight refractory multi-principal alloys do not meet the requirements. The lower strength makes it difficult to resist wear and deformation, and often leads to severe adhesion or abrasive wear behavior during friction.

[0003] Studies have shown that introducing a second phase into the matrix is ​​considered a common strategy to improve the wear resistance of alloys at medium and low temperatures. The hard second phase can effectively enhance the strength and hardness of the matrix, and correspondingly alleviate the severe plastic deformation of the matrix below the wear surface and the adhesive wear during subsequent friction. However, the above strategy has a drawback: the introduced hard second phase is usually difficult to shear deform. As the friction progresses, stress concentration may occur at the interface, leading to crack nucleation and severe wear and fracture behavior. Therefore, introducing a hard and shear-deformable second phase into the alloy to alleviate stress concentration has become the key to improving wear performance, but related research is still very scarce. Summary of the invention

[0004] The present invention aims to provide a novel α2 phase-reinforced refractory multi-principal alloy and a preparation method thereof, which can solve the current problems of low strength and poor wear performance of such alloys and is expected to be applied to wear-resistant mechanical parts. A needle-shaped α2 phase is introduced into the BCC matrix of the alloy using simple thermal processing and aging treatment. Due to the high load-bearing and shear deformation behavior of the α2 phase, the yield strength and wear deformation resistance of the alloy material are comprehensively improved, and the fracture behavior during friction and wear is correspondingly alleviated.

[0005] The chemical expression of the α2 phase strengthened refractory multi-principal alloy of the present invention is Ti 50 Zr 30 Nb 10 Al 10 , the preparation method is as follows: 1) According to the atomic ratio of each element in the alloy chemical formula, weigh the corresponding weight of Ti, Zr, Nb and Al pure metal blocks, place them in a suspension melting furnace for melting, and obtain a cast alloy after the melt is cooled; In step 1), the purity of Ti, Zr, Nb and Al single metal blocks is greater than 99.5%, and ultrasonic cleaning is required to remove surface impurities before smelting. The cast alloy should be remelted 3 to 8 times to ensure homogenization.

[0006] 2) using an electric spark cutting machine to process the cast alloy obtained in step 1) into a plate with a length of 30-40 mm, a width of 10-15 mm, and a thickness of 10-15 mm, and then placing it in a spark plasma sintering furnace for hot pressing treatment, the temperature is controlled at 880° C. to 920° C., and the reduction rate is controlled at 70% to 80% to refine the grains and introduce a large number of small-angle grain boundaries; In step 2), when hot pressing is performed in the spark plasma sintering furnace, the vacuum degree needs to be controlled below 2 Pa to avoid unnecessary oxidation affecting the performance. The hot pressing process is as follows: (I) the cast alloy plate is placed in the spark plasma sintering furnace, and the furnace temperature is raised to 880 ℃~920 ℃ at a heating rate of 100 ℃ / min, and no axial pressure is applied during this period; (II) after reaching the processing temperature requirement, axial pressure is applied at a rate of 0.4 t / min, and the displacement change is monitored with the furnace. When the reduction rate reaches 70%~80%, the pressure is stopped.

[0007] 3) placing the hot pressed alloy plate in step 2) in a vacuum tube furnace for aging treatment, wherein the aging temperature is controlled at 580°C to 620°C, and the aging time is controlled at 40 to 50 hours. After the aging treatment is completed, the plate is cooled in the furnace to finally obtain the prepared α2 phase strengthened refractory multi-principal alloy.

[0008] In step 3), when performing aging treatment in a vacuum tube furnace, the vacuum degree needs to be lower than 2 Pa to avoid unnecessary oxidation affecting the performance.

[0009] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a novel α2 phase strengthened Ti 50 Zr 30 Nb 10 Al 10Refractory multi-principal alloy, with excellent mechanical and tribological properties. Through simple hot working and aging treatment processes, favorable changes in microstructure and properties are induced. Due to the high load-bearing and shear deformation behavior of the hard α2 phase, the tensile yield strength of the alloy is increased by 44% and the wear rate is reduced by 52%. The whole process is simple, efficient, easy to operate and low-cost. The prepared alloy is expected to be a potential candidate material for high-strength and wear-resistant functional parts and be used in the aerospace field. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 XRD patterns of the three alloys prepared in Examples 1-3.

[0011] Figure 2 SEM images of the three alloys prepared in Examples 1-3: (a) Base alloy, (b) 900HP75 alloy, (c) and (d) Aged alloy Figure 3 Nanoindentation images of different regions of the Aged alloy prepared in Example 3: (a) Optical microscope morphology of the indentation region, (b) Typical load-displacement curve of the region selected in Figure a Figure 4 Room temperature tensile stress-strain curves of the three alloys prepared in Examples 1-3.

[0012] Figure 5 Wear scar cross-sectional profiles and wear rate statistics of the three alloys prepared in Examples 1-3 after room temperature friction testing: (a) wear scar cross-sectional profiles, (b) wear rate statistics.

[0013] Figure 6 Characterization of the microstructural changes after the friction test of Example 1 and Example 3: (a) SEM image of the wear surface of Example 1, (b) SEM image of the wear surface of Example 3, (c) TEM image of the wear cross section of Example 3, (d, e) local enlarged images of the selected area in Figure c. DETAILED DESCRIPTION

[0014] The present invention is further explained below with reference to specific embodiments.

[0015] Example 1 S1. According to the atomic ratio of the alloy, weigh the corresponding mass of Ti, Zr, Nb, and Al pure metal blocks, and place them in a suspension melting furnace for melting. Remelting is required for 5 times to ensure homogenization. After the melt is cooled, a cast alloy is obtained. Then, an electric spark cutting machine is used to process the cast alloy into plates with a length of 35 mm, a width of 12 mm, and a thickness of 10 mm. S2. Place the cast alloy plate obtained in step S1 in a spark plasma sintering furnace. When the vacuum degree is reduced to below 2Pa, increase the furnace temperature to 1200℃ at a heating rate of 100℃ / min. During this period, no axial pressure is applied. (II) After reaching the processing temperature requirement, axial pressure is applied at a rate of 0.4t / min. Use the built-in displacement detection system of the spark plasma sintering furnace to monitor the displacement change. When the reduction rate reaches 40%, stop the pressure immediately and end the program to finally obtain the desired hot pressed alloy plate. The alloy in this state is named Base alloy.

[0016] Example 2 S1. According to the atomic ratio of the alloy, weigh the corresponding mass of Ti, Zr, Nb, and Al pure metal blocks, and place them in a suspension melting furnace for melting. Remelting is required for 5 times to ensure homogeneity. After the melt is cooled, a cast alloy is obtained. Then, an electric spark cutting machine is used to process the cast alloy into a plate with a length of 35 mm, a width of 12 mm, and a thickness of 10 mm.

[0017] S2. Place the cast alloy plate obtained in step S1 in a spark plasma sintering furnace. When the vacuum degree is reduced to below 2Pa, increase the furnace temperature to 900℃ at a heating rate of 100℃ / min. During this period, no axial pressure is applied. (II) After the processing temperature requirement is reached, axial pressure is applied at a rate of 0.4t / min. Use the built-in displacement detection system of the spark plasma sintering furnace to monitor the displacement change. When the reduction rate reaches 75%, stop applying pressure immediately and end the program to finally obtain the desired hot pressed alloy plate. The alloy in this state is named 900HP75 alloy.

[0018] Example 3 S1. According to the atomic ratio of the alloy, weigh the corresponding mass of Ti, Zr, Nb, and Al pure metal blocks, and place them in a suspension melting furnace for melting. Remelting is required for 5 times to ensure homogeneity. After the melt is cooled, a cast alloy is obtained. Then, an electric spark cutting machine is used to process the cast alloy into a plate with a length of 35 mm, a width of 12 mm, and a thickness of 10 mm.

[0019] S2. Place the cast alloy plate obtained in step S1 in a spark plasma sintering furnace. When the vacuum degree drops below 2 Pa, increase the furnace temperature to 900°C at a heating rate of 100°C / min. During this period, no axial pressure is applied. (II) After the processing temperature requirement is reached, axial pressure is applied at a rate of 0.4t / min. Use the built-in displacement detection system of the spark plasma sintering furnace to monitor the displacement change. When the reduction rate reaches 75%, stop applying pressure immediately and end the program to obtain the desired hot pressed alloy plate. S3, placing the hot pressed alloy sheet in step S2 in a vacuum tube furnace for aging treatment, controlling the aging temperature to 600°C, the aging time to 48 hours, and the vacuum degree in the furnace to be less than 2 Pa. After the aging treatment is completed, the furnace is cooled to finally obtain the prepared strengthened alloy, which is named Aged alloy.

[0020] The structural characterization and performance evaluation of the three states of refractory multi-principal alloys prepared in Examples 1-3 are as follows: Figure 1 The XRD patterns of the three alloys prepared in Examples 1-3 show that the Base alloy and the 900HP75 alloy are single BCC phases, and the phase composition of the Aged alloy is BCC+α2 phase.

[0021] Figure 2 The SEM images of the three alloys prepared in Examples 1-3 show that the Base alloy and the 900HP75 alloy are single BCC phases. After hot pressing at 900 ℃, the grain size of the 900HP75 alloy is significantly reduced compared to the Base alloy. The grain size of the Aged alloy is comparable to that of the 900HP75 alloy, except that a large amount of needle-shaped α2 phase is introduced into the BCC matrix.

[0022] Figure 3 Nanoindentation images of different areas of the Aged alloy show that the nanohardness of the BCC matrix is ​​(4.23±0.17) GPa, the nanohardness of the α2 phase inside the grains is (4.86±0.21) GPa, and the nanohardness of the α2 phase at the grain boundary is (5.89±0.30) GPa.

[0023] Figure 4 The room temperature tensile stress-strain curves of the three alloys prepared in Examples 1-3 are shown in Table 1. -3 S -1 Under the same conditions, the yield strength and fracture strain of the Base alloy were (750±14) MPa and (17.7±0.5)%, the yield strength and fracture strain of the 900HP75 alloy were (928±16) MPa and (12.9±0.8)%, and the yield strength and fracture strain of the Aged alloy were (1081±26) MPa and (5.4±0.3)%.

[0024] Figure 5 The wear scar cross-sectional profile and wear rate statistics of the three alloys prepared in Examples 1-3 after room temperature friction test. The three alloys were subjected to sliding friction test with Si3N4 with a diameter of 6 mm under the parameters of 5 N load, 5 Hz reciprocating frequency and 30 min friction time. The results showed that the wear rate and maximum wear depth of the Base alloy were (12.7±0.62) ×10-4 mm 3 / (N·m) and 97.2 µm, the wear rate and maximum wear depth of 900HP75 alloy are (9.87±0.58) ×10 - 4 mm 3 / (N·m) and 84.9 µm, the wear rate and maximum wear depth of Aged alloy are (6.1±0.7) ×10 -4 mm 3 / (N·m) and 65.3 µm.

[0025] Figure 6 Characterization of the microstructural changes after the friction test of Example 1 and Example 3. Figure 6 a shows that the Base alloy underwent obvious plastic deformation and material fracture after the friction test, and had poor wear resistance. Figure 6 b shows that the Aged alloy only underwent slight plastic deformation and fracture after the friction test, and had good wear resistance. Figure 6 c is the TEM morphology of the wear cross section of Aged alloy after friction test. Figure 6 d and Figure 6 e is Figure 6 c Local magnification of the selected area, showing the shear deformation behavior of the α2 phase.

Claims

1. An α2 phase strengthened refractory multi-principal alloy with high tensile strength and high wear resistance, characterized in that: The chemical expression of the α2 phase strengthened refractory multi-principal alloy is Ti 50 Zr 30 Nb 10 Al 10 .

2. A method for preparing the α2 phase strengthened refractory multi-principal alloy as claimed in claim 1, characterized in that: The following steps are involved: 1) According to the atomic ratio of each element in the alloy chemical formula, weigh the corresponding weight of Ti, Zr, Nb and Al pure metal blocks, place them in a suspension melting furnace for melting, and obtain a cast alloy after the melt is cooled; 2) using an electric spark cutting machine to process the cast alloy obtained in step 1) into a plate with a length of 30-40 mm, a width of 10-15 mm, and a thickness of 10-15 mm, and then placing it in a spark plasma sintering furnace for hot pressing treatment, the temperature is controlled at 880° C. to 920° C., and the reduction rate is controlled at 70% to 80%, to obtain a hot pressed alloy plate; 3) placing the hot pressed alloy plate in step 2) in a vacuum tube furnace for aging treatment, wherein the aging temperature is controlled at 580°C to 620°C, and the aging time is controlled at 40 to 50 hours. After the aging treatment is completed, the plate is cooled in the furnace to finally obtain the prepared α2 phase strengthened refractory multi-principal alloy.

3. The method for preparing the α2 phase strengthened refractory multi-principal alloy according to claim 2, characterized in that: In step 1), the purity of the Ti, Zr, Nb and Al single metal blocks is greater than 99.5%, and ultrasonic cleaning is required to remove surface impurities before smelting.

4. The method for preparing the α2 phase strengthened refractory multi-principal alloy according to claim 2, characterized in that: In step 1), the cast alloy should be remelted 3 to 8 times to ensure homogenization.

5. The method for preparing the α2 phase strengthened refractory multi-principal alloy according to claim 2, characterized in that: In step 2), when the material is placed in a spark plasma sintering furnace for hot pressing, the vacuum degree needs to be controlled below 2 Pa.

6. The method for preparing the α2 phase strengthened refractory multi-principal alloy according to claim 2, characterized in that: In step 2), the hot pressing process is specifically as follows: (I) placing the cast alloy plate in a spark plasma sintering furnace, raising the furnace temperature to 880°C~920°C at a heating rate of 100°C / min, and not applying any axial pressure during this period; (II) after reaching the processing temperature requirement, applying axial pressure at a rate of 0.4 t / min, and monitoring the displacement change with the furnace. When the reduction rate reaches 70%~80%, stop applying pressure.

7. The method for preparing the α2 phase strengthened refractory multi-principal alloy according to claim 2, characterized in that: In step 3), when performing aging treatment in a vacuum tube furnace, the vacuum degree needs to be lower than 2 Pa.

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