Volume 53,Issue 12,2024 Table of Contents
Liu Na
,
Zhao Zhanglong
,
Liu Yuli
,
Feng Kaikai
,
Zha Xiaohui
,
Li Pu
,
Xu Wenxin
,
Yang Haiou
,
Lai Yunjin
2024, 53(12):3281-3290.
DOI: 10.12442/j.issn.1002-185X.20240097
Abstract:
Near-α titanium alloy and Ti2AlNb alloy powders premixed with different proportions were prepared on the near-α titanium alloy substrate by laser deposition technique, and the microstructure characteristics were analyzed and discussed. Results show that numerous river-like sub-grain structures are formed inside the equiaxed B2 grains of the laser-deposited premixed titanium alloy powders with the proportion of Ti2AlNb above 40wt%, whereas the needle-like structure within coarse columnar β grains exist with the proportion of Ti2AlNb below 40wt%. It is noteworthy that the decrease in laser power and scanning speed can accelerate the formation of sub-grain structures. Based on the analysis of experimental results, it can be inferred that the formation of sub-grain structure not only is related to the precipitation of O phase due to composition micro-segregation at sub-grain boundaries, but also is inseparable from the stacking faults caused by the internal stress during the laser deposition.
Near-α titanium alloy and Ti2AlNb alloy powders premixed with different proportions were prepared on the near-α titanium alloy substrate by laser deposition technique, and the microstructure characteristics were analyzed and discussed. Results show that numerous river-like sub-grain structures are formed inside the equiaxed B2 grains of the laser-deposited premixed titanium alloy powders with the proportion of Ti2AlNb above 40wt%, whereas the needle-like structure within coarse columnar β grains exist with the proportion of Ti2AlNb below 40wt%. It is noteworthy that the decrease in laser power and scanning speed can accelerate the formation of sub-grain structures. Based on the analysis of experimental results, it can be inferred that the formation of sub-grain structure not only is related to the precipitation of O phase due to composition micro-segregation at sub-grain boundaries, but also is inseparable from the stacking faults caused by the internal stress during the laser deposition.
2024, 53(12):3383-3389.
DOI: 10.12442/j.issn.1002-185X.20230717
Abstract:
The creep behavior of equiaxed, duplex and widmanstatten structures of Ti6321 alloy under tensile stress of 706MPa for 200h was studied. The microstructure morphology of the samples after creep was observed by metallographic microscope and transmission electron microscope (TEM), and the dislocation slip types of different microstructures of Ti6321 alloy were analyzed by trace method. The results show that the creep strain of equiaxed structure of Ti6321 alloy is the largest, followed by duplex structure and widmanstatten structure. Through the first derivative of creep curve, the turning point of creep rate change was found, and the creep strain of different stages was obtained. It is found that the primary creep strain is positively related to the amount of residual dislocation in the structure. The creep mechanism of Ti6321 alloy at room temperature is mainly dislocation slip, the original cellular dislocation decomposes and the new dislocation slip forms during the tensile process of equiaxed structure, the new dislocation is (10-11)<11-23> cross slip; the primary α phase of duplex structure mainly occurs {10-10}<11-20> prismatic slip, the secondary α phase occurs (-1101)<-2110> pyramidal slip; widmanstatten structure starts (0001)<-2110> basal slip and (10-11)<10-12> pyramidal slip.
The creep behavior of equiaxed, duplex and widmanstatten structures of Ti6321 alloy under tensile stress of 706MPa for 200h was studied. The microstructure morphology of the samples after creep was observed by metallographic microscope and transmission electron microscope (TEM), and the dislocation slip types of different microstructures of Ti6321 alloy were analyzed by trace method. The results show that the creep strain of equiaxed structure of Ti6321 alloy is the largest, followed by duplex structure and widmanstatten structure. Through the first derivative of creep curve, the turning point of creep rate change was found, and the creep strain of different stages was obtained. It is found that the primary creep strain is positively related to the amount of residual dislocation in the structure. The creep mechanism of Ti6321 alloy at room temperature is mainly dislocation slip, the original cellular dislocation decomposes and the new dislocation slip forms during the tensile process of equiaxed structure, the new dislocation is (10-11)<11-23> cross slip; the primary α phase of duplex structure mainly occurs {10-10}<11-20> prismatic slip, the secondary α phase occurs (-1101)<-2110> pyramidal slip; widmanstatten structure starts (0001)<-2110> basal slip and (10-11)<10-12> pyramidal slip.
2024, 53(12):3422-3427.
DOI: 10.12442/j.issn.1002-185X.20230630
Abstract:
The research utilizes the constant strain rate method to systematically investigate the superplastic behavior of fine-grained TC4 alloy sheets under temperature conditions of 880-920 °C and strain rate conditions of 0.0005 s-1-0.005 s-1. Furthermore, the study encompasses a comprehensive analysis characterizing the microstructural evolution during the superplastic deformation. This study reveals that with the elevation of superplastic deformation temperature, the alloy consistently undergoes conspicuous dynamic recrystallization. This phenomenon results the transformation in the superplastic deformation mechanisms of the alloy. At 880°C with a strain rate of 0.001 s-1, the alloy exhibits a cooperative superplastic deformation mechanism involving grain boundary sliding, grain rotation and sliding. Under these conditions, TC4 alloy achieves an elongation of up to 1039%, accompanied by a notable strain sensitivity coefficient (m-value) of 0.51. In contrast, at 920°C with a strain rate of 0.001 s-1, the alloy"s superplasticity predominantly relies on grain boundary sliding and intragranular dislocation glide, resulting in a diminished elongation of 746% and a reduced m-value of 0.39. These research findings elucidate the critical factors behind the varying superplastic performance of TC4 alloy across distinct temperature and strain rate conditions，which is significant to further study the complex mechanical behavior and deformation mechanism of TC4 titanium alloy during superplastic deformation.
The research utilizes the constant strain rate method to systematically investigate the superplastic behavior of fine-grained TC4 alloy sheets under temperature conditions of 880-920 °C and strain rate conditions of 0.0005 s-1-0.005 s-1. Furthermore, the study encompasses a comprehensive analysis characterizing the microstructural evolution during the superplastic deformation. This study reveals that with the elevation of superplastic deformation temperature, the alloy consistently undergoes conspicuous dynamic recrystallization. This phenomenon results the transformation in the superplastic deformation mechanisms of the alloy. At 880°C with a strain rate of 0.001 s-1, the alloy exhibits a cooperative superplastic deformation mechanism involving grain boundary sliding, grain rotation and sliding. Under these conditions, TC4 alloy achieves an elongation of up to 1039%, accompanied by a notable strain sensitivity coefficient (m-value) of 0.51. In contrast, at 920°C with a strain rate of 0.001 s-1, the alloy"s superplasticity predominantly relies on grain boundary sliding and intragranular dislocation glide, resulting in a diminished elongation of 746% and a reduced m-value of 0.39. These research findings elucidate the critical factors behind the varying superplastic performance of TC4 alloy across distinct temperature and strain rate conditions，which is significant to further study the complex mechanical behavior and deformation mechanism of TC4 titanium alloy during superplastic deformation.
2024, 53(12):3447-3456.
DOI: 10.12442/j.issn.1002-185X.20230646
Abstract:
In this study, the deformation mechanism of single-crystal titanium was investigated by molecular dynamics simulation, the temperature was 500~1000K, the strain rate was "0.0001" 〖"ps" 〗^"-1" ~"0.01" 〖"ps" 〗^"-1" , and the loading mode was tensile and compressive, and the results were subjected to the stress-strain analysis, potential analysis, coevolutionary neighbourhood analysis and dislocation density analysis. The results show that with the increase of temperature, the yield strength decreases, and the strain value corresponding to the yield point decreases; at the same temperature, the tensile yield strength is slightly higher than the compressive yield strength; the modulus of elasticity does not change much under different loading rates, and the yield strength increases with the increase of loading rate. With the increase of temperature or loading rate, the peak potential energy of the system increases. As the strain proceeds, the HCP structure decreases, the Other structure increases, and the BCC and FCC structures appear and increase (except at the deformation temperature of 1000K); after exceeding the yield point, the various structures gradually tend to stabilise; with the increase of temperature, the transformation of crystal structure occurs earlier. The dislocation density decreases with increasing temperature, and the total dislocation density under tensile load is larger than that under compressive load; The main types of dislocations throughout the deformation process are Other dislocations, 1/3<-1100>dislocations and 1/3<11-20> dislocations.
In this study, the deformation mechanism of single-crystal titanium was investigated by molecular dynamics simulation, the temperature was 500~1000K, the strain rate was "0.0001" 〖"ps" 〗^"-1" ~"0.01" 〖"ps" 〗^"-1" , and the loading mode was tensile and compressive, and the results were subjected to the stress-strain analysis, potential analysis, coevolutionary neighbourhood analysis and dislocation density analysis. The results show that with the increase of temperature, the yield strength decreases, and the strain value corresponding to the yield point decreases; at the same temperature, the tensile yield strength is slightly higher than the compressive yield strength; the modulus of elasticity does not change much under different loading rates, and the yield strength increases with the increase of loading rate. With the increase of temperature or loading rate, the peak potential energy of the system increases. As the strain proceeds, the HCP structure decreases, the Other structure increases, and the BCC and FCC structures appear and increase (except at the deformation temperature of 1000K); after exceeding the yield point, the various structures gradually tend to stabilise; with the increase of temperature, the transformation of crystal structure occurs earlier. The dislocation density decreases with increasing temperature, and the total dislocation density under tensile load is larger than that under compressive load; The main types of dislocations throughout the deformation process are Other dislocations, 1/3<-1100>dislocations and 1/3<11-20> dislocations.
2024, 53(12):3457-3464.
DOI: 10.12442/j.issn.1002-185X.20230647
Abstract:
Quadratic regression orthogonal experiment was used to study the influence of different process parameters on the formability results of plasma fuse additive manufacturing. The results show that the welding speed has the greatest influence on the welding width, and the interaction between power and welding speed has the least influence on the welding width. The effect of wire feeding speed on melting height is the greatest, and the repetition of welding speed has the least effect on melting height. The interaction between power and wire feed rate has the greatest influence on aspect ratio, and the welding speed has the least influence on aspect ratio. The melting depth is mainly affected by the heat input, that is, the power. The error between the predicted value and the actual value of the quadratic regression model is less than 10%, and the predicted result is good. It is suitable for the additive manufacturing process of RT-1400 titanium alloy plasma fuse: P(welding power)= 3KW, WFS(wire feed speed)= 2.4m /min, Ts(scanning speed)=0.2m/min, welding pass spacing is 5.3mm, using interlayer orthogonal scanning mode.
Quadratic regression orthogonal experiment was used to study the influence of different process parameters on the formability results of plasma fuse additive manufacturing. The results show that the welding speed has the greatest influence on the welding width, and the interaction between power and welding speed has the least influence on the welding width. The effect of wire feeding speed on melting height is the greatest, and the repetition of welding speed has the least effect on melting height. The interaction between power and wire feed rate has the greatest influence on aspect ratio, and the welding speed has the least influence on aspect ratio. The melting depth is mainly affected by the heat input, that is, the power. The error between the predicted value and the actual value of the quadratic regression model is less than 10%, and the predicted result is good. It is suitable for the additive manufacturing process of RT-1400 titanium alloy plasma fuse: P(welding power)= 3KW, WFS(wire feed speed)= 2.4m /min, Ts(scanning speed)=0.2m/min, welding pass spacing is 5.3mm, using interlayer orthogonal scanning mode.
2024, 53(12):3503-3513.
DOI: 10.12442/j.issn.1002-185X.20230672
Abstract:
In this work, the hot rolling process of Ti-44Al-5Nb-1Mo-2V-0.2B thick plates was simulated using the Marc finite element simulation software. A three-dimensional thermomechanical coupled finite element model was established to analyze the temperature, equivalent stress, and equivalent strain at various positions of the TiAl alloy during rolling, with a particular focus on the distribution characteristics of equivalent plastic strain along the thickness direction of the thick plates. Subsequently, the hot-pack rolling of the Ti-44Al-5Nb-1Mo-2V-0.2B alloy was performed based on the simulation results. The investigation encompassed the evolution of the microstructure along the thickness direction of the TiAl alloy and the impact of the primary rolling on its thermal deformation capacity. The obtained results reveal that the microstructure of the primary rolled sheets predominantly comprises a small amount of residual laminae and fine mixed phases consisting of B2, γ, and α2. The equivalent plastic strain increases gradually from the edge to the center of the sheets, leading to the significant softening of the microstructure in the center of the sheets. This effect induces a corresponding decrease in the residual laminae content from the edge to the center. Consequently, the preparation process for the Ti-44Al-5Nb-1Mo-2V-0.2B alloy was determined based on the influence of the hot rolling process on the microstructure. During the rolling process, as the sheet thickness decreases, it is advisable to appropriately increase the number of reheating cycles or extend the reheating time and simultaneously reduce the amount of rolling deformation. This approach helps minimize the temperature and strain distribution gradient from the core to the edge of the sheets. Additionally, in the later stages of the rolling process, further refinement of the microstructure can be achieved by raising the rolling temperature.
In this work, the hot rolling process of Ti-44Al-5Nb-1Mo-2V-0.2B thick plates was simulated using the Marc finite element simulation software. A three-dimensional thermomechanical coupled finite element model was established to analyze the temperature, equivalent stress, and equivalent strain at various positions of the TiAl alloy during rolling, with a particular focus on the distribution characteristics of equivalent plastic strain along the thickness direction of the thick plates. Subsequently, the hot-pack rolling of the Ti-44Al-5Nb-1Mo-2V-0.2B alloy was performed based on the simulation results. The investigation encompassed the evolution of the microstructure along the thickness direction of the TiAl alloy and the impact of the primary rolling on its thermal deformation capacity. The obtained results reveal that the microstructure of the primary rolled sheets predominantly comprises a small amount of residual laminae and fine mixed phases consisting of B2, γ, and α2. The equivalent plastic strain increases gradually from the edge to the center of the sheets, leading to the significant softening of the microstructure in the center of the sheets. This effect induces a corresponding decrease in the residual laminae content from the edge to the center. Consequently, the preparation process for the Ti-44Al-5Nb-1Mo-2V-0.2B alloy was determined based on the influence of the hot rolling process on the microstructure. During the rolling process, as the sheet thickness decreases, it is advisable to appropriately increase the number of reheating cycles or extend the reheating time and simultaneously reduce the amount of rolling deformation. This approach helps minimize the temperature and strain distribution gradient from the core to the edge of the sheets. Additionally, in the later stages of the rolling process, further refinement of the microstructure can be achieved by raising the rolling temperature.
2024, 53(12):3291-3298.
DOI: 10.12442/j.issn.1002-185X.20240023
Abstract:
A 2D transient mathematical model was established to separately describe the anode bubble dynamics and the bubble-induced electrolyte motion in the rare earth electrolysis cell with horizontal electrode. Results indicate that with the increase in the anode inclined angle, the maximum bubble thickness is increased gradually. Furthermore, compared with the conventional anode, the inclined and chamfered anodes are conductive to the bubble length reduction and the bubble velocity improvement. Meanwhile, the bubble-induced electrolyte motion in the electrolysis cell can improve the distribution and transport process of oxyfluorides, thereby enhancing the current efficiency. Finally, a novel feeding method based on the electrolyte flow is proposed.
A 2D transient mathematical model was established to separately describe the anode bubble dynamics and the bubble-induced electrolyte motion in the rare earth electrolysis cell with horizontal electrode. Results indicate that with the increase in the anode inclined angle, the maximum bubble thickness is increased gradually. Furthermore, compared with the conventional anode, the inclined and chamfered anodes are conductive to the bubble length reduction and the bubble velocity improvement. Meanwhile, the bubble-induced electrolyte motion in the electrolysis cell can improve the distribution and transport process of oxyfluorides, thereby enhancing the current efficiency. Finally, a novel feeding method based on the electrolyte flow is proposed.
Hao Juan
,
Wang Baichuan
,
Ding Yuhang
,
Yang Chao
,
Jiang Bailing
,
Wang Ziyi
,
Wang Donghong
,
Dong Dan
2024, 53(12):3299-3305.
DOI: 10.12442/j.issn.1002-185X.20240043
Abstract:
TiN coatings were prepared by the novel dual-stage high power impulse magnetron sputtering (HIPIMS) technique under different deposition time conditions, and the effects of microstructure and stress state at different coating growth stages on the mechanical, tribological, and corrosion resistance performance of the coatings were analyzed. Results show that with the prolongation of deposition time from 30 min to 120 min, the surface structure of TiN coating exhibits a round cell structure with tightly doped small and large particles, maintaining the atomic stacking thickening mechanism of deposition-crystallization-growth. When the deposition time increases from 90 min to 120 min, the coating thickness increases from 3884 nm to 4456 nm, and the stress state of coating undergoes the compression-tension transition. When the deposition time is 90 min, TiN coating structure is dense and suffers relatively small compressive stress of -0.54 GPa. The coating has high hardness and elastic modulus, which are 27.5 and 340.2 GPa, respectively. Meanwhile, good tribological properties (average friction coefficient of 0.52, minimum wear rate of 1.68×10-4 g/s) and fine corrosion resistance properties (minimum corrosion current density of 1.0632×10-8 A·cm-2, minimum corrosion rate of 5.5226×10-5 mm·A-1) can also be obtained for the coatings.
TiN coatings were prepared by the novel dual-stage high power impulse magnetron sputtering (HIPIMS) technique under different deposition time conditions, and the effects of microstructure and stress state at different coating growth stages on the mechanical, tribological, and corrosion resistance performance of the coatings were analyzed. Results show that with the prolongation of deposition time from 30 min to 120 min, the surface structure of TiN coating exhibits a round cell structure with tightly doped small and large particles, maintaining the atomic stacking thickening mechanism of deposition-crystallization-growth. When the deposition time increases from 90 min to 120 min, the coating thickness increases from 3884 nm to 4456 nm, and the stress state of coating undergoes the compression-tension transition. When the deposition time is 90 min, TiN coating structure is dense and suffers relatively small compressive stress of -0.54 GPa. The coating has high hardness and elastic modulus, which are 27.5 and 340.2 GPa, respectively. Meanwhile, good tribological properties (average friction coefficient of 0.52, minimum wear rate of 1.68×10-4 g/s) and fine corrosion resistance properties (minimum corrosion current density of 1.0632×10-8 A·cm-2, minimum corrosion rate of 5.5226×10-5 mm·A-1) can also be obtained for the coatings.
2024, 53(12):3306-3312.
DOI: 10.12442/j.issn.1002-185X.20240067
Abstract:
Alumina coatings doped with different precious metals were prepared by cathode plasma electrolytic deposition. Results show that the porosity of precious metal-doped alumina coatings (especially Al2O3-Ru) decreases, and the high-temperature cyclic oxidation resistance and spallation resistance are enhanced. The Al2O3-Ru composite coating shows better effect: its average oxidation rate K and average amount of oxide spallation G are minimum. Meanwhile, Nernst equation was used to explain the simultaneous deposition of precious metal and alumina, and the whole process and mechanism of deposition were analyzed.
Alumina coatings doped with different precious metals were prepared by cathode plasma electrolytic deposition. Results show that the porosity of precious metal-doped alumina coatings (especially Al2O3-Ru) decreases, and the high-temperature cyclic oxidation resistance and spallation resistance are enhanced. The Al2O3-Ru composite coating shows better effect: its average oxidation rate K and average amount of oxide spallation G are minimum. Meanwhile, Nernst equation was used to explain the simultaneous deposition of precious metal and alumina, and the whole process and mechanism of deposition were analyzed.
2024, 53(12):3313-3320.
DOI: 10.12442/j.issn.1002-185X.20240091
Abstract:
The microstructure and mechanical properties of Inconel 617 alloy rolled at room temperature with different deformation degrees (20%, 50%, 70%) were investigated. The grain refinement mechanism and main texture types of Inconel 617 alloy during rolling were analyzed via electron backscatter diffraction and X-ray diffraction, and the microhardness and tensile properties of Inconel 617 alloy with different deformation degrees were tested. Results reveal that the grains of Inconel 617 alloy are refined during the rolling deformation process, and the refinement mechanism is the fragmentation of original grains caused by the increase in dis-location density and strain gradient. The main microtextures of the rolled samples are Goss {011}<001>, Rotated Goss {110}<110>, Brass {011}<211>, and P {011}<112> textures, and their intensity is increased with increase in deformation degree. After rolling deformation, the strength of the Inconel 617 alloy is improved and the ductility is reduced by the combined effect of grain refinement and dislocation strengthening. Comprehensively, the yield strength and elongation of Inconel 617 alloy after 20% deformation are 772.48 MPa and 0.1962, respectively, presenting good synergy effect.
The microstructure and mechanical properties of Inconel 617 alloy rolled at room temperature with different deformation degrees (20%, 50%, 70%) were investigated. The grain refinement mechanism and main texture types of Inconel 617 alloy during rolling were analyzed via electron backscatter diffraction and X-ray diffraction, and the microhardness and tensile properties of Inconel 617 alloy with different deformation degrees were tested. Results reveal that the grains of Inconel 617 alloy are refined during the rolling deformation process, and the refinement mechanism is the fragmentation of original grains caused by the increase in dis-location density and strain gradient. The main microtextures of the rolled samples are Goss {011}<001>, Rotated Goss {110}<110>, Brass {011}<211>, and P {011}<112> textures, and their intensity is increased with increase in deformation degree. After rolling deformation, the strength of the Inconel 617 alloy is improved and the ductility is reduced by the combined effect of grain refinement and dislocation strengthening. Comprehensively, the yield strength and elongation of Inconel 617 alloy after 20% deformation are 772.48 MPa and 0.1962, respectively, presenting good synergy effect.
2024, 53(12):3321-3328.
DOI: 10.12442/j.issn.1002-185X.20240249
Abstract:
The surface of magnesium alloy was laser-processed, and the laser-etched morphology was determined as grooves by observing the surface morphology of sheep rib bone. The wettability of different morphologies was investigated by contact angle test. Through the cell adhesion test, the effects of different morphologies on cell adhesion, growth and migration were investigated. Results show that the wetting angle of the block-shaped surface is smaller than that of the groove-shaped surface, and block-shaped surface has better hydrophilicity. Compared with the smooth surface, the block-shaped surface has better cell adhesion, and the depressions and bumps are full of cells, suggesting that the micropatterns prepared by the laser processing are conducive to the enhancement of biocompatibility.
The surface of magnesium alloy was laser-processed, and the laser-etched morphology was determined as grooves by observing the surface morphology of sheep rib bone. The wettability of different morphologies was investigated by contact angle test. Through the cell adhesion test, the effects of different morphologies on cell adhesion, growth and migration were investigated. Results show that the wetting angle of the block-shaped surface is smaller than that of the groove-shaped surface, and block-shaped surface has better hydrophilicity. Compared with the smooth surface, the block-shaped surface has better cell adhesion, and the depressions and bumps are full of cells, suggesting that the micropatterns prepared by the laser processing are conducive to the enhancement of biocompatibility.
12 Enhancement in Mechanical Properties of TiAl Alloys by In-Situ Precipitation of Hybrid TiB2-Ti2AlN
2024, 53(12):3329-3337.
DOI: 10.12442/j.issn.1002-185X.20240001
Abstract:
TiAl alloy was mixed with BN nanoplates and then sintered at 1300 °C through spark plasma sintering technique, and the hybrid TiB2-Ti2AlN/TiAl composites were in-situ prepared. The microstructural evolution and mechanical properties at room temperature of TiAl composites were investigated. Results show that a fully lamellar microstructure can be achieved in the TiAl composites with BN nanoplates of lower content, whereas a transformation to the nearly lamellar microstructure can be observed under higher BN nanoplate content conditions. The microstructure of TiAl composites is significantly refined due to the even distribution of in-situ prepared TiB2-Ti2AlN particles at the lamellar colony boundaries. Notably, a continuous core-shell structure of TiB2-Ti2AlN particles is formed at the lamellar grain boundary after adding 0.5wt% BN nanoplates. The results of compression and friction wear at room temperature show that the hardness and compressive strength of TiAl composites are greatly improved with the increase in BN nanoplate content from 0wt% to 1wt%. Meanwhile, the average coefficient of friction decreases from 0.59 to 0.47, and the wear rate decreases by 29.9%. These remarkable mechanical properties are mainly attributed to the strengthening effects of the in-situ formation of TiB2-Ti2AlN particles, refined microstructure, and core-shell structure.
TiAl alloy was mixed with BN nanoplates and then sintered at 1300 °C through spark plasma sintering technique, and the hybrid TiB2-Ti2AlN/TiAl composites were in-situ prepared. The microstructural evolution and mechanical properties at room temperature of TiAl composites were investigated. Results show that a fully lamellar microstructure can be achieved in the TiAl composites with BN nanoplates of lower content, whereas a transformation to the nearly lamellar microstructure can be observed under higher BN nanoplate content conditions. The microstructure of TiAl composites is significantly refined due to the even distribution of in-situ prepared TiB2-Ti2AlN particles at the lamellar colony boundaries. Notably, a continuous core-shell structure of TiB2-Ti2AlN particles is formed at the lamellar grain boundary after adding 0.5wt% BN nanoplates. The results of compression and friction wear at room temperature show that the hardness and compressive strength of TiAl composites are greatly improved with the increase in BN nanoplate content from 0wt% to 1wt%. Meanwhile, the average coefficient of friction decreases from 0.59 to 0.47, and the wear rate decreases by 29.9%. These remarkable mechanical properties are mainly attributed to the strengthening effects of the in-situ formation of TiB2-Ti2AlN particles, refined microstructure, and core-shell structure.
13 Effect of Compression Passes on Mechanical Properties and Corrosion Behavior of ZK60 Magnesium Alloy
2024, 53(12):3338-3347.
DOI: 10.12442/j.issn.1002-185X.20240102
Abstract:
The impact of multi-directional compression passes on the microstructure, mechanical properties, and corrosion behavior of ZK60 magnesium alloy was investigated. Results reveal that severe dendrite segregation exists in the as-cast ZK60 magnesium alloy with coarse MgZn phases distributed along the grain boundaries. After 9 passes of compression, the coarse solidified phases at the grain boundary are significantly refined, and back dissolution occurs. Fine recrystallized grains accompanied with the fine diffused nano-phases emerge in the local area around the large grains. The tensile strength of ZK60 magnesium alloy generally exhibits the upward trend with the increase in compression passes, whereas the compression rate shows the downward trend. The compressive strength reaches 433.6 MPa with the compression rate of 21.3% after 9 passes of compression. Multi-directional compression can significantly reduce the degradation rate of ZK60 magnesium alloy in simulated body fluids. Furthermore, it is observed that in the as-cast ZK60 magnesium alloy, micro-segregation can easily lead to severe intragranular local corrosion. However, after multi-directional compression, the tendency to intragranular local corrosion is significantly diminished.
The impact of multi-directional compression passes on the microstructure, mechanical properties, and corrosion behavior of ZK60 magnesium alloy was investigated. Results reveal that severe dendrite segregation exists in the as-cast ZK60 magnesium alloy with coarse MgZn phases distributed along the grain boundaries. After 9 passes of compression, the coarse solidified phases at the grain boundary are significantly refined, and back dissolution occurs. Fine recrystallized grains accompanied with the fine diffused nano-phases emerge in the local area around the large grains. The tensile strength of ZK60 magnesium alloy generally exhibits the upward trend with the increase in compression passes, whereas the compression rate shows the downward trend. The compressive strength reaches 433.6 MPa with the compression rate of 21.3% after 9 passes of compression. Multi-directional compression can significantly reduce the degradation rate of ZK60 magnesium alloy in simulated body fluids. Furthermore, it is observed that in the as-cast ZK60 magnesium alloy, micro-segregation can easily lead to severe intragranular local corrosion. However, after multi-directional compression, the tendency to intragranular local corrosion is significantly diminished.
2024, 53(12):3348-3357.
DOI: 10.12442/j.issn.1002-185X.20240011
Abstract:
Preparation method of magnetic nanoparticles with core-shell structure was introduced, especially focusing on the preparation principle of sol-gel method, microemulsion method, and self-assembly technique. The application of core-shell nanoparticles in precision machining was discussed. The Fe3O4@SiO2 composite particles were prepared by sol-gel method and were applied to the magnetorheological polishing of titanium alloy plates. Results show that core-shell nanoparticles with higher surface quality can be obtained after processing, compared with those after conventional abrasives. After polishing for 20 min, the surface roughness of the workpiece reaches 23 nm and the scratches are effectively reduced. Finally, the preparation and application of core-shell nanoparticles are summarized and prospected to provide a reference for further research on core-shell nanoparticles.
Preparation method of magnetic nanoparticles with core-shell structure was introduced, especially focusing on the preparation principle of sol-gel method, microemulsion method, and self-assembly technique. The application of core-shell nanoparticles in precision machining was discussed. The Fe3O4@SiO2 composite particles were prepared by sol-gel method and were applied to the magnetorheological polishing of titanium alloy plates. Results show that core-shell nanoparticles with higher surface quality can be obtained after processing, compared with those after conventional abrasives. After polishing for 20 min, the surface roughness of the workpiece reaches 23 nm and the scratches are effectively reduced. Finally, the preparation and application of core-shell nanoparticles are summarized and prospected to provide a reference for further research on core-shell nanoparticles.
2024, 53(12):3373-3382.
DOI: 10.12442/j.issn.1002-185X.20230572
Abstract:
This study employs vacuum arc melting technology to fabricate FexCrMnAlCu (x=0, 0.5, 1, 1.5, 2) high-entropy alloys. The phase structure and microstructure of the alloys before and after corrosion were characterized using XRD, SEM, and EDS. The corrosion behavior and oxide film composition of the alloys in a 3.5% NaCl solution were investigated through potentiodynamic polarization curves, EIS, XPS, and immersion tests. The results indicate that FexCrMnAlCu high-entropy alloys exhibit a dual-phase structure of BCC+FCC. The addition of Fe enhances the intensity of the BCC phase diffraction peaks. As the Fe content increases, the alloy"s corrosion resistance initially improves and then deteriorates. Alloys with added Fe exhibit superior corrosion resistance compared to those without Fe. This is attributed to the change in grain size caused by the addition of Fe, which alters the number of grain boundaries per unit area, consequently affecting the corrosion resistance. The primary type of corrosion observed in FexCrMnAlCu alloys is intergranular corrosion. After corrosion, an oxide film composed of various elemental oxides forms on the alloy surface. The Fe1.5CrMnAlCu alloy exhibits the lowest self-corrosion current density (1.75×10-6 A/cm2), the most positive self-corrosion potential (-0.589 V), and the largest impedance arc radius.
This study employs vacuum arc melting technology to fabricate FexCrMnAlCu (x=0, 0.5, 1, 1.5, 2) high-entropy alloys. The phase structure and microstructure of the alloys before and after corrosion were characterized using XRD, SEM, and EDS. The corrosion behavior and oxide film composition of the alloys in a 3.5% NaCl solution were investigated through potentiodynamic polarization curves, EIS, XPS, and immersion tests. The results indicate that FexCrMnAlCu high-entropy alloys exhibit a dual-phase structure of BCC+FCC. The addition of Fe enhances the intensity of the BCC phase diffraction peaks. As the Fe content increases, the alloy"s corrosion resistance initially improves and then deteriorates. Alloys with added Fe exhibit superior corrosion resistance compared to those without Fe. This is attributed to the change in grain size caused by the addition of Fe, which alters the number of grain boundaries per unit area, consequently affecting the corrosion resistance. The primary type of corrosion observed in FexCrMnAlCu alloys is intergranular corrosion. After corrosion, an oxide film composed of various elemental oxides forms on the alloy surface. The Fe1.5CrMnAlCu alloy exhibits the lowest self-corrosion current density (1.75×10-6 A/cm2), the most positive self-corrosion potential (-0.589 V), and the largest impedance arc radius.
Zhang Xiao
,
Wang Kuaishe
,
Feng Pengfa
,
An geng
,
Bu Chunyang
,
Hu Ping
,
Xi Sha
,
Li Jing
,
Zhou Sha
2024, 53(12):3390-3397.
DOI: 10.12442/j.issn.1002-185X.20230773
Abstract:
The hot deformation behavior of pre-deformation Mo-0.3La alloy was studied on the Gleeble-3500 thermal-mechanical simulator at 973～1273K with the rate of deformation 0.001～0.1 s-1 and the true strain of 60%, and the constitutive equation was established by hyperbolic sine model with Zene-Hollomon parameter. The results show that in this experimental conditions, the dynamic recrystallization characteristics of the true stress-strain curves are observed. Pre-deformation Mo-0.3La alloy, at high strain rate 0.1 s?1 or low temperature 973K exhibits workhardening, dynamic recrystallization is significant at low strain rates (0.001 and 0.005s-1) of 1273K. The high angle grain boundaries of the pre-deformation alloy is 31.65%. After redeformation, the high grain boundary decreases to 17.14%, and there are a small amount of recrystallized grains(6.08%), with the increase of deformation temperature, high grain boundaries and recrystallized grains increase. Calculated by the constitutive equation, the deformation activation energy Q is 287.08 kJ/mol, and the stress exponent n is 14.40. Using this equation, the average relative error between the theoretical calculations and experimental results is only 3.25%.
The hot deformation behavior of pre-deformation Mo-0.3La alloy was studied on the Gleeble-3500 thermal-mechanical simulator at 973～1273K with the rate of deformation 0.001～0.1 s-1 and the true strain of 60%, and the constitutive equation was established by hyperbolic sine model with Zene-Hollomon parameter. The results show that in this experimental conditions, the dynamic recrystallization characteristics of the true stress-strain curves are observed. Pre-deformation Mo-0.3La alloy, at high strain rate 0.1 s?1 or low temperature 973K exhibits workhardening, dynamic recrystallization is significant at low strain rates (0.001 and 0.005s-1) of 1273K. The high angle grain boundaries of the pre-deformation alloy is 31.65%. After redeformation, the high grain boundary decreases to 17.14%, and there are a small amount of recrystallized grains(6.08%), with the increase of deformation temperature, high grain boundaries and recrystallized grains increase. Calculated by the constitutive equation, the deformation activation energy Q is 287.08 kJ/mol, and the stress exponent n is 14.40. Using this equation, the average relative error between the theoretical calculations and experimental results is only 3.25%.
2024, 53(12):3398-3406.
DOI: 10.12442/j.issn.1002-185X.20230809
Abstract:
The solution enthalpy and the excess entropy of Zr in αU have been calculated based on first principles calculations in order to achieve U-rich solubility curves for U-Zr phase diagram. The enthalpy and the excess entropy of the Zr atom corresponding to Zr-αU transforming from solution state into δUZr2 are 1.437 eV/Zr atom and 1.060 kB/Zr atom by using the SQS model, which are 1.420 eV/Zr atom and 0. 732 kB/Zr atom with the disorder structure for δUZr2. But based on the experimental data, the fitted solution enthalpy and excess entropy are -0.823±0.712 meV/Zr atom and 5.880±9.976 kB/Zr atom, respectively. Through comparing the theoretical calculations and the experimental fitting results, it is found that the effect of the vibrational entropy on solubility could not be ignored. This discrepancy between the theoretical results and the experimental data might be related to the fact that the positions of Zr in δUZr2 in the theoretical calculations are not well consistent with the specific structural parameters of the the experimental samples.
The solution enthalpy and the excess entropy of Zr in αU have been calculated based on first principles calculations in order to achieve U-rich solubility curves for U-Zr phase diagram. The enthalpy and the excess entropy of the Zr atom corresponding to Zr-αU transforming from solution state into δUZr2 are 1.437 eV/Zr atom and 1.060 kB/Zr atom by using the SQS model, which are 1.420 eV/Zr atom and 0. 732 kB/Zr atom with the disorder structure for δUZr2. But based on the experimental data, the fitted solution enthalpy and excess entropy are -0.823±0.712 meV/Zr atom and 5.880±9.976 kB/Zr atom, respectively. Through comparing the theoretical calculations and the experimental fitting results, it is found that the effect of the vibrational entropy on solubility could not be ignored. This discrepancy between the theoretical results and the experimental data might be related to the fact that the positions of Zr in δUZr2 in the theoretical calculations are not well consistent with the specific structural parameters of the the experimental samples.
2024, 53(12):3407-3412.
DOI: 10.12442/j.issn.1002-185X.20230812
Abstract:
Multi-metal composites can integrate the properties of a single component to obtain the high perforcemance and multifunctions that are difficult to be achieved by the conventional methods, which have promising application prospects. Here, it was proposed a novel approach to prepare lamellar multi-metal composites by selective laser melting and vacuum melt infiltration technology. Using Cu/316L as a model material, successfully prepared composites with delicate lamellar structure, investigated the effect of configuration variations on the properties of the composites. The results show that the properties of the lamellar composites are significantly anisotropic. With the increase of the thickness of the 316L layer, the compressive strength and the elastic modulus of the composites increase, and the electrical conductivity slightly decreases, reaching 1.96, 1.34, and 0.9 times of that of pure copper, respectively. Owing to the structural optimization (micron-scale laminations) and component selection (copper and stainless steel), the composites possess both outstanding toughness and good electrical conductivity. Moreover, the methodology provided in this work is novel and universal, providing a new approach for the design and preparation of high-performance and multifunctional composites.
Multi-metal composites can integrate the properties of a single component to obtain the high perforcemance and multifunctions that are difficult to be achieved by the conventional methods, which have promising application prospects. Here, it was proposed a novel approach to prepare lamellar multi-metal composites by selective laser melting and vacuum melt infiltration technology. Using Cu/316L as a model material, successfully prepared composites with delicate lamellar structure, investigated the effect of configuration variations on the properties of the composites. The results show that the properties of the lamellar composites are significantly anisotropic. With the increase of the thickness of the 316L layer, the compressive strength and the elastic modulus of the composites increase, and the electrical conductivity slightly decreases, reaching 1.96, 1.34, and 0.9 times of that of pure copper, respectively. Owing to the structural optimization (micron-scale laminations) and component selection (copper and stainless steel), the composites possess both outstanding toughness and good electrical conductivity. Moreover, the methodology provided in this work is novel and universal, providing a new approach for the design and preparation of high-performance and multifunctional composites.
2024, 53(12):3413-3421.
DOI: 10.12442/j.issn.1002-185X.20230623
Abstract:
The true stress-strain curve of the metal beryllium was obtained under deformation temperature of 250 ℃~450 ℃ and strain rate of 10-1 s-1-10-4 s-1 by the isothermal compression testing which was conducted in the Instron 5582 universal material testing machine, and thus flow behaviors of the metal beryllium was studied in the first plastic peak zone. The results indicate that the flow stress of the metal beryllium increases with the increase of strain rate and decreases with the increase of deformation temperature under the experimental conditions. Furthermore, the flow stress is more sensitive to the variation of temperature. The flow stresses show a decreasing trend with the increase of strain after work hardening to a certain extent under various deformation conditions, especially 250 ℃/10-1 s-1, theSflowSstressShasSaSpeakSvalue. Moreover, the deformation activation energy of the metal beryllium decreases from 244.95 kJ/mol to 166.82 kJ/mol as the strain increases. These results indicate that softening mechanism of the metal beryllium deformed in the first plastic peak zone is influenced by dynamic recrystallization, but the main softening mechanism is still recovery. It was established that an Arrhenius strain compensated constitutive equation that includes strain variables. The equation can accurately predict the flow stress of the metal beryllium during compression deformation in the first plastic peak zone, and the maximum mean relative estimation error (MRE) of the prediction is 5.0550%, and the minimum correlation coefficient (R) is 0.9899.
The true stress-strain curve of the metal beryllium was obtained under deformation temperature of 250 ℃~450 ℃ and strain rate of 10-1 s-1-10-4 s-1 by the isothermal compression testing which was conducted in the Instron 5582 universal material testing machine, and thus flow behaviors of the metal beryllium was studied in the first plastic peak zone. The results indicate that the flow stress of the metal beryllium increases with the increase of strain rate and decreases with the increase of deformation temperature under the experimental conditions. Furthermore, the flow stress is more sensitive to the variation of temperature. The flow stresses show a decreasing trend with the increase of strain after work hardening to a certain extent under various deformation conditions, especially 250 ℃/10-1 s-1, theSflowSstressShasSaSpeakSvalue. Moreover, the deformation activation energy of the metal beryllium decreases from 244.95 kJ/mol to 166.82 kJ/mol as the strain increases. These results indicate that softening mechanism of the metal beryllium deformed in the first plastic peak zone is influenced by dynamic recrystallization, but the main softening mechanism is still recovery. It was established that an Arrhenius strain compensated constitutive equation that includes strain variables. The equation can accurately predict the flow stress of the metal beryllium during compression deformation in the first plastic peak zone, and the maximum mean relative estimation error (MRE) of the prediction is 5.0550%, and the minimum correlation coefficient (R) is 0.9899.
Wang Fanqiang
,
Shi Qi
,
Liu Xin
,
Liu Binbin
,
Tan Chong
,
Xie Huanwen
,
Shen Zhengyan
,
Zeng Meiqin
2024, 53(12):3428-3436.
DOI: 10.12442/j.issn.1002-185X.20230632
Abstract:
WMoTaNbV refractory high-entropy alloy spherical powder was prepared by mechanical alloying and radio frequency plasma spheroidization using elemental powder as raw material. Focused on studying the influence of ball milling time and radio frequency plasma spheroidization process on powder phase, morphology, particle size and impurity content, and used X-ray diffractometer, scanning electron microscope, transmission electron microscope, carbon sulfur meter, oxygen nitrogen and hydrogen meter and Laser particle size analyzer, etc. are used to analyze and characterize the powder properties. The results show that as the ball milling time increases, the low melting point elements gradually become solid solution to the high melting point elements. When the ball milling time is 14 h, refractory high-entropy alloy powder with a single BCC phase structure can be formed. The particle size gradually becomes refined with the prolongation of the ball milling time, and the impurity content increases with the prolongation of the ball milling time. Powder milled for 2 h was selected for radio frequency plasma spheroidization. The median particle size of the spheroidized powder was 66.0 μm, the oxygen and carbon contents were 540 ppm and 210 ppm respectively, and the powder flowability was significantly improved to 8.4 s·(50 g)? 1, the tap density reaches 8.80 g·cm?3.
WMoTaNbV refractory high-entropy alloy spherical powder was prepared by mechanical alloying and radio frequency plasma spheroidization using elemental powder as raw material. Focused on studying the influence of ball milling time and radio frequency plasma spheroidization process on powder phase, morphology, particle size and impurity content, and used X-ray diffractometer, scanning electron microscope, transmission electron microscope, carbon sulfur meter, oxygen nitrogen and hydrogen meter and Laser particle size analyzer, etc. are used to analyze and characterize the powder properties. The results show that as the ball milling time increases, the low melting point elements gradually become solid solution to the high melting point elements. When the ball milling time is 14 h, refractory high-entropy alloy powder with a single BCC phase structure can be formed. The particle size gradually becomes refined with the prolongation of the ball milling time, and the impurity content increases with the prolongation of the ball milling time. Powder milled for 2 h was selected for radio frequency plasma spheroidization. The median particle size of the spheroidized powder was 66.0 μm, the oxygen and carbon contents were 540 ppm and 210 ppm respectively, and the powder flowability was significantly improved to 8.4 s·(50 g)? 1, the tap density reaches 8.80 g·cm?3.
2024, 53(12):3437-3446.
DOI: 10.12442/j.issn.1002-185X.20230633
Abstract:
Corrosion and wear are the main factors affecting the service life of key mechanical parts. Therefore, it is of great significance to study new wear-resistant and corrosion-resistant materials. As emerging materials, high entropy alloy (HEA) and medium entropy alloy (MEA) have special microstructure and excellent properties, which have become research hotspots of wear and corrosion resistant materials. In this paper, (AlCoCrFeNi)80wt. %/(CoCrNi)20wt. % composites with excellent wear and corrosion resistance were prepared by SLM technology. And it was annealed. The effects of different annealing temperatures (600 °C, 800 °C, 1000 °C) on the microstructure, hardness, wear resistance and corrosion resistance of (AlCoCrFeNi)80wt. %/(CoCrNi)20wt. % were studied by means of X-ray diffraction, scanning electron microscopy, energy spectrum analysis, electron backscatter diffraction, hardness tester, friction and wear tester, electrochemical workstation and X-ray photoelectron spectroscopy. After annealing at 600 °C, the phase composition of the composites does not change, which is composed of BCC phase and B2 phase, and the grains are more uniform and fine than before annealing. After annealing at 800 °C and 1000 °C, the FCC phase appears and the grains are coarser. The higher the annealing temperature, the heavier the FCC and the larger the grain size. With the increase of annealing temperature, the hardness and wear resistance of the composites increase first and then decrease. Due to the fine grain strengthening effect, the hardness and wear resistance of the sample annealed at 600 °C were the highest. Compared with the sample before annealing, the hardness increased by 26.9 % and the wear weight loss decreased by 32 %. Annealing treatment promoted the enrichment of Cr2O3 in the passive film and improved the corrosion resistance of the composites.
Corrosion and wear are the main factors affecting the service life of key mechanical parts. Therefore, it is of great significance to study new wear-resistant and corrosion-resistant materials. As emerging materials, high entropy alloy (HEA) and medium entropy alloy (MEA) have special microstructure and excellent properties, which have become research hotspots of wear and corrosion resistant materials. In this paper, (AlCoCrFeNi)80wt. %/(CoCrNi)20wt. % composites with excellent wear and corrosion resistance were prepared by SLM technology. And it was annealed. The effects of different annealing temperatures (600 °C, 800 °C, 1000 °C) on the microstructure, hardness, wear resistance and corrosion resistance of (AlCoCrFeNi)80wt. %/(CoCrNi)20wt. % were studied by means of X-ray diffraction, scanning electron microscopy, energy spectrum analysis, electron backscatter diffraction, hardness tester, friction and wear tester, electrochemical workstation and X-ray photoelectron spectroscopy. After annealing at 600 °C, the phase composition of the composites does not change, which is composed of BCC phase and B2 phase, and the grains are more uniform and fine than before annealing. After annealing at 800 °C and 1000 °C, the FCC phase appears and the grains are coarser. The higher the annealing temperature, the heavier the FCC and the larger the grain size. With the increase of annealing temperature, the hardness and wear resistance of the composites increase first and then decrease. Due to the fine grain strengthening effect, the hardness and wear resistance of the sample annealed at 600 °C were the highest. Compared with the sample before annealing, the hardness increased by 26.9 % and the wear weight loss decreased by 32 %. Annealing treatment promoted the enrichment of Cr2O3 in the passive film and improved the corrosion resistance of the composites.
2024, 53(12):3465-3474.
DOI: 10.12442/j.issn.1002-185X.20230655
Abstract:
The precipitation behavior and dissolution behavior of η-phase of 718Plus alloy are studied. By the thermal compression with different compression amount, the effect of different quantities of η-phase on the recrystallization was studied. Recrystallization behaviors of samples with little η-phase compressed at different conditions were studied. The results show that, the peak temperature of η-phase precipitation occurred at 900℃. The dissolve behavior of η-phase was mainly effected by solution time, and it dissolve effectively after 2 hours at temperature of 1040℃. Small quantity of η-phase contributes to dynamic recrystallization in large deformation process while large quantity of η-phase restrain dynamic recrystallization. At appropriate deformation temperature and rate, small quantity of η-phase interacted with the dynamic recrystallization process, which makes for the uniform fine crystal structure.
The precipitation behavior and dissolution behavior of η-phase of 718Plus alloy are studied. By the thermal compression with different compression amount, the effect of different quantities of η-phase on the recrystallization was studied. Recrystallization behaviors of samples with little η-phase compressed at different conditions were studied. The results show that, the peak temperature of η-phase precipitation occurred at 900℃. The dissolve behavior of η-phase was mainly effected by solution time, and it dissolve effectively after 2 hours at temperature of 1040℃. Small quantity of η-phase contributes to dynamic recrystallization in large deformation process while large quantity of η-phase restrain dynamic recrystallization. At appropriate deformation temperature and rate, small quantity of η-phase interacted with the dynamic recrystallization process, which makes for the uniform fine crystal structure.
2024, 53(12):3475-3484.
DOI: 10.12442/j.issn.1002-185X.20230656
Abstract:
Three nickel-based powder superalloys FGH4113A (WZ-A3), FGH96 and FGH97 were subjected to oxidation tests in air at 815, 900 and 1000℃. Static weight gain method was used to determine the oxidation dynamics curve of the alloys at different temperatures and to evaluate the oxidation resistance. The surface and cross-sectional morphology, composition and structure of specimens were analyzed after oxidation tests by X-ray diffraction, scanning electron microscopy, energy spectrometer. The results showed that the three alloys were completely antioxidant grade at 815 and 900℃, WZ-A3, FGH96 and FGH97 were antioxidant grade, secondary antioxidant grade and complete antioxidant grade respectively at 1000℃.The oxide layers of WZ-A3 and FGH96 alloys were similar after oxidation at a high temperature of 1000℃, which consisted of an outermost layer TiO2, a middle layer mixed layer of Cr2O3 and a small amount of TiO2, an innermost layer was dendritic Al2O3. There was the enrichment of Nb and Mo elements at the boundary between the middle and the innermost layer for WZ-A3. The difference in oxidation properties of the three alloys was related to Al content. Al content was low in WZ-A3 and FGH96 and the dendritic Al2O3 layer formed can’t effectively form isolation. After the Cr2O3 reaction, it evaporated to form holes, which destroys the density of the oxide layer at high temperatures. Al content in FGH97 was high such that the formation of a dense Al2O3 layer on the surface can effectively block the outward diffusion of other alloying elements after oxidation at 1000℃, so the FGH97 exhibited excellent oxidation resistance. The addition of 1.0wt%Ta and 1.2wt%Nb has improved the oxidation resistance of WZ-A3 alloy to a certain extent.
Three nickel-based powder superalloys FGH4113A (WZ-A3), FGH96 and FGH97 were subjected to oxidation tests in air at 815, 900 and 1000℃. Static weight gain method was used to determine the oxidation dynamics curve of the alloys at different temperatures and to evaluate the oxidation resistance. The surface and cross-sectional morphology, composition and structure of specimens were analyzed after oxidation tests by X-ray diffraction, scanning electron microscopy, energy spectrometer. The results showed that the three alloys were completely antioxidant grade at 815 and 900℃, WZ-A3, FGH96 and FGH97 were antioxidant grade, secondary antioxidant grade and complete antioxidant grade respectively at 1000℃.The oxide layers of WZ-A3 and FGH96 alloys were similar after oxidation at a high temperature of 1000℃, which consisted of an outermost layer TiO2, a middle layer mixed layer of Cr2O3 and a small amount of TiO2, an innermost layer was dendritic Al2O3. There was the enrichment of Nb and Mo elements at the boundary between the middle and the innermost layer for WZ-A3. The difference in oxidation properties of the three alloys was related to Al content. Al content was low in WZ-A3 and FGH96 and the dendritic Al2O3 layer formed can’t effectively form isolation. After the Cr2O3 reaction, it evaporated to form holes, which destroys the density of the oxide layer at high temperatures. Al content in FGH97 was high such that the formation of a dense Al2O3 layer on the surface can effectively block the outward diffusion of other alloying elements after oxidation at 1000℃, so the FGH97 exhibited excellent oxidation resistance. The addition of 1.0wt%Ta and 1.2wt%Nb has improved the oxidation resistance of WZ-A3 alloy to a certain extent.
2024, 53(12):3485-3492.
DOI: 10.12442/j.issn.1002-185X.20230664
Abstract:
The (Ti + B4C) / AA7075 composite powder with 5 wt.% and B4C ceramic particles (3 wt.%, 5 wt.%, 10 wt.%) was prepared by high-energy ball grinding, and several groups of additive samples were prepared by laser melting deposition technology (Laser Melting Deposition, LMD). The influence of titanium elements and different mass fractions B4C ceramic powder on the microscopic organization and mechanical properties of the composite materials was studied. The results show that the addition of spherical pure titanium powder and B4C ceramic particles can effectively solve the stoma and cracking problems of 7075 aluminum alloy during LMD molding process. When the mass fraction of B4C was 3 wt.%, the average microhardness and tensile strength of the composite were 141.65 HV 0.2 and 336.93 MPa, respectively, which were 41.5 % and 68.4 % higher than 100.07 HV 0.2 and 200.05 MPa of the deposited 7075 aluminum alloy. Later, with the increase of B4C mass score from 3 wt.% to 10 wt.%, the tensile strength of the sample gradually decreased, but the wear resistance gradually increased, the average friction coefficient decreased from 0.83 to 0.78, and the wear form changed from adhesive wear to peeling wear.
The (Ti + B4C) / AA7075 composite powder with 5 wt.% and B4C ceramic particles (3 wt.%, 5 wt.%, 10 wt.%) was prepared by high-energy ball grinding, and several groups of additive samples were prepared by laser melting deposition technology (Laser Melting Deposition, LMD). The influence of titanium elements and different mass fractions B4C ceramic powder on the microscopic organization and mechanical properties of the composite materials was studied. The results show that the addition of spherical pure titanium powder and B4C ceramic particles can effectively solve the stoma and cracking problems of 7075 aluminum alloy during LMD molding process. When the mass fraction of B4C was 3 wt.%, the average microhardness and tensile strength of the composite were 141.65 HV 0.2 and 336.93 MPa, respectively, which were 41.5 % and 68.4 % higher than 100.07 HV 0.2 and 200.05 MPa of the deposited 7075 aluminum alloy. Later, with the increase of B4C mass score from 3 wt.% to 10 wt.%, the tensile strength of the sample gradually decreased, but the wear resistance gradually increased, the average friction coefficient decreased from 0.83 to 0.78, and the wear form changed from adhesive wear to peeling wear.
2024, 53(12):3493-3502.
DOI: 10.12442/j.issn.1002-185X.20230667
Abstract:
Objective To solve the connection problem of TC4-7075 heteroalloy with large differences in physical parameters, and to expand the application range of high specific strength titanium-aluminum heteroalloy composite structure. Methods AlTiVNbSi high-entropy alloy was selected as the intermediate layer material, and the effective connection of TC4 and AA7075 heteroalloys was realized by laser melting deposition technology, and the macromorphology, microstructure, component distribution and interface characteristics of the junction area were characterized by metallographic microscopy (OM), scanning electron microscopy (SEM, EBSD), microhardness and tensile experiment. Results The connection joint is well combined with the TC4 titanium alloy side interface, and there is an interface transition zone with a width of about 20μm, TC4 near the interface has bundled Weisler tissue, and a compound area with a width of 20μm exists at the 7075 side interface. Conclusion Based on AlTiVNbSi as the intermediate layer material of high-entropy alloy, laser melting deposition technology can realize the effective connection of titanium-aluminum heteroalloy, the hardness of the joint is about 696HV, which is higher than the hardness of the base metal, the hardness of the connecting zone on the near titanium side is higher than that of the connecting zone on the aluminum side, and the tensile strength is 116MPa.
Objective To solve the connection problem of TC4-7075 heteroalloy with large differences in physical parameters, and to expand the application range of high specific strength titanium-aluminum heteroalloy composite structure. Methods AlTiVNbSi high-entropy alloy was selected as the intermediate layer material, and the effective connection of TC4 and AA7075 heteroalloys was realized by laser melting deposition technology, and the macromorphology, microstructure, component distribution and interface characteristics of the junction area were characterized by metallographic microscopy (OM), scanning electron microscopy (SEM, EBSD), microhardness and tensile experiment. Results The connection joint is well combined with the TC4 titanium alloy side interface, and there is an interface transition zone with a width of about 20μm, TC4 near the interface has bundled Weisler tissue, and a compound area with a width of 20μm exists at the 7075 side interface. Conclusion Based on AlTiVNbSi as the intermediate layer material of high-entropy alloy, laser melting deposition technology can realize the effective connection of titanium-aluminum heteroalloy, the hardness of the joint is about 696HV, which is higher than the hardness of the base metal, the hardness of the connecting zone on the near titanium side is higher than that of the connecting zone on the aluminum side, and the tensile strength is 116MPa.
2024, 53(12):3358-3372.
DOI: 10.12442/j.issn.1002-185X.20240059
Abstract:
Semi-solid processing (SSP) technique is an important method for metal casting. Products made by SSP technique have advantages such as small solidification shrinkage, high dimensional accuracy of castings, fast forming speed, high productivity, and good mechanical properties. Aluminum alloy products produced by SSP technique can be heat-treated. The mechanical properties of the products after heat treatment are similar to those of steel, but they have the lighter mass and are widely used in many fields. Semi-solid slurry preparation technique is one of the key techniques in the field of aluminum alloy semi-solid forming, which determines the industrial application of semi-solid forming and also has significant impact on the quality of aluminum alloy semi-solid slurry. Semi-solid slurry preparation technique with the continuous development has become the emerging technique in the field of metal processing. The principles, advantages and disadvantages of various semi-solid slurry preparation techniques for metal materials were reviewed, and the future trends of semi-solid slurry preparation techniques were predicted.
Semi-solid processing (SSP) technique is an important method for metal casting. Products made by SSP technique have advantages such as small solidification shrinkage, high dimensional accuracy of castings, fast forming speed, high productivity, and good mechanical properties. Aluminum alloy products produced by SSP technique can be heat-treated. The mechanical properties of the products after heat treatment are similar to those of steel, but they have the lighter mass and are widely used in many fields. Semi-solid slurry preparation technique is one of the key techniques in the field of aluminum alloy semi-solid forming, which determines the industrial application of semi-solid forming and also has significant impact on the quality of aluminum alloy semi-solid slurry. Semi-solid slurry preparation technique with the continuous development has become the emerging technique in the field of metal processing. The principles, advantages and disadvantages of various semi-solid slurry preparation techniques for metal materials were reviewed, and the future trends of semi-solid slurry preparation techniques were predicted.
2024, 53(12):3514-3525.
DOI: 10.12442/j.issn.1002-185X.20230652
Abstract:
Aluminum-lithium alloys, as a new type of aerospace material, have a wide range of application prospects due to their advantages of low density, high specific strength and specific stiffness. Existing research on Al-Li alloys focuses on microalloying and hot processing (e.g., hot extrusion, heat treatment, etc.), but neglects the fact that the quality of the original Al-Li alloy ingot prior to the hot processing step also has a great impact on the final properties of the alloy. However, not much research has been done on the melting and solidification forming technologies for Al-Li alloy ingots. Therefore, this paper reviews and summarizes the preparation techniques of Al-Li alloy ingots from both high-vacuum and non-vacuum environments, including spray forming, powder metallurgy, and ultrasonic-assisted extrusion casting forming process. This paper analyzes the advantages and disadvantages of these technologies in depth, and puts forward some new ideas or prospects for the preparation of Al-Li alloy ingots.
Aluminum-lithium alloys, as a new type of aerospace material, have a wide range of application prospects due to their advantages of low density, high specific strength and specific stiffness. Existing research on Al-Li alloys focuses on microalloying and hot processing (e.g., hot extrusion, heat treatment, etc.), but neglects the fact that the quality of the original Al-Li alloy ingot prior to the hot processing step also has a great impact on the final properties of the alloy. However, not much research has been done on the melting and solidification forming technologies for Al-Li alloy ingots. Therefore, this paper reviews and summarizes the preparation techniques of Al-Li alloy ingots from both high-vacuum and non-vacuum environments, including spray forming, powder metallurgy, and ultrasonic-assisted extrusion casting forming process. This paper analyzes the advantages and disadvantages of these technologies in depth, and puts forward some new ideas or prospects for the preparation of Al-Li alloy ingots.
2024, 53(12):3526-3538.
DOI: 10.12442/j.issn.1002-185X.20230653
Abstract:
Owing to its high specific strength, creep resistance, oxidation resistance and low density, titanium aluminide alloy (TiAl) is regarded as an ideal candidate material to replace nickel-based superalloys for the fabrication of engine turbine blades used in aerospace applications. However, its application is restricted by the poor plasticity at room temperature and difficulties in hot shaping. Comparing with conventional subtractive manufacturing process, selective laser melting possesses some unique advantages such as short lead time, high processing resolution, near-net shape forming, etc. Therefore, it can be used to remedy the deficiency of conventional subtractive manufacturing process and accelerate the application of TiAl. This paper summarized the research progress of titanium aluminide manufactured by selective laser melting at home and abroad. The effect of chemical composition, powder morphology, printing parameters and post-printing heat treatment on the printing defects, phase constitutes, microstructure and mechanical properties were reviewed comprehensively. Finally, we outlooked the future developing directions of SLM TiAl.
Owing to its high specific strength, creep resistance, oxidation resistance and low density, titanium aluminide alloy (TiAl) is regarded as an ideal candidate material to replace nickel-based superalloys for the fabrication of engine turbine blades used in aerospace applications. However, its application is restricted by the poor plasticity at room temperature and difficulties in hot shaping. Comparing with conventional subtractive manufacturing process, selective laser melting possesses some unique advantages such as short lead time, high processing resolution, near-net shape forming, etc. Therefore, it can be used to remedy the deficiency of conventional subtractive manufacturing process and accelerate the application of TiAl. This paper summarized the research progress of titanium aluminide manufactured by selective laser melting at home and abroad. The effect of chemical composition, powder morphology, printing parameters and post-printing heat treatment on the printing defects, phase constitutes, microstructure and mechanical properties were reviewed comprehensively. Finally, we outlooked the future developing directions of SLM TiAl.
2024, 53(12):3539-3552.
DOI: 10.12442/j.issn.1002-185X.20230766
Abstract:
Tungsten and it’s alloys not only have the advantages of high melting point, high density and excellent resistance to plasma sputtering erosion, but also have excellent comprehensive mechanical properties in the high-temperature service environment, which is the indispensable key of material for aerospace, weapons and equipment, nuclear engineering and so on. However, tungsten alloy faces the problem of large scale and uneven distribution of strengthening phase in the extreme high temperature service environment that resulting in insufficient high temperature strength and toughness. In order to solve the above problems, domestic and foreign scholars have carried out research on the strength and toughness of tungsten alloy, and improved the mechanical properties of tungsten alloy by adjusting the material composition and microstructure. In this paper, the structure control and toughening mechanism of tungsten alloy are discussed from three aspects: deformation strengthening, solution strengthening and dispersion strengthening, and the future development trend and unsolved problems of tungsten alloy are prospected.
Tungsten and it’s alloys not only have the advantages of high melting point, high density and excellent resistance to plasma sputtering erosion, but also have excellent comprehensive mechanical properties in the high-temperature service environment, which is the indispensable key of material for aerospace, weapons and equipment, nuclear engineering and so on. However, tungsten alloy faces the problem of large scale and uneven distribution of strengthening phase in the extreme high temperature service environment that resulting in insufficient high temperature strength and toughness. In order to solve the above problems, domestic and foreign scholars have carried out research on the strength and toughness of tungsten alloy, and improved the mechanical properties of tungsten alloy by adjusting the material composition and microstructure. In this paper, the structure control and toughening mechanism of tungsten alloy are discussed from three aspects: deformation strengthening, solution strengthening and dispersion strengthening, and the future development trend and unsolved problems of tungsten alloy are prospected.
2024, 53(12):3553-3568.
DOI: 10.12442/j.issn.1002-185X.20230604
Abstract:
Uranium is an important strategic nuclear material, widely used in energy systems and defense industries. However, uranium is easily corroded quickly by the environmental atmosphere in service, which not only produces radioactive corrosion products but also poses a serious threat to service performance and life. Although research on the corrosion of uranium has been carried out for decades, the understanding of the corrosion behavior of uranium is not clear because of its radioactivity, fast corrosion rate, and various corrosion products. Based on the relevant research on the corrosion behavior of uranium in oxygen, water vapor, and oxygen-containing water vapor, this paper briefly introduces the typical corrosion products of uranium, and reviews the current research status of uranium corrosion kinetics from the aspects of corrosion kinetics model, corrosion rate equation and activation energy. This paper reviews the research progress on the corrosion mechanism of uranium from the aspects of the dissociation diffusion of corrosive media and the evolution of key intermediate corrosion products, summarizes the current clear and unified understanding, points out the current controversial issues in the research field, and looks forward to the main research directions in the future, providing research basis for the corrosion assessment, life prediction and corrosion protection of uranium.
Uranium is an important strategic nuclear material, widely used in energy systems and defense industries. However, uranium is easily corroded quickly by the environmental atmosphere in service, which not only produces radioactive corrosion products but also poses a serious threat to service performance and life. Although research on the corrosion of uranium has been carried out for decades, the understanding of the corrosion behavior of uranium is not clear because of its radioactivity, fast corrosion rate, and various corrosion products. Based on the relevant research on the corrosion behavior of uranium in oxygen, water vapor, and oxygen-containing water vapor, this paper briefly introduces the typical corrosion products of uranium, and reviews the current research status of uranium corrosion kinetics from the aspects of corrosion kinetics model, corrosion rate equation and activation energy. This paper reviews the research progress on the corrosion mechanism of uranium from the aspects of the dissociation diffusion of corrosive media and the evolution of key intermediate corrosion products, summarizes the current clear and unified understanding, points out the current controversial issues in the research field, and looks forward to the main research directions in the future, providing research basis for the corrosion assessment, life prediction and corrosion protection of uranium.
