Based on the deforming technique of severe plastic deformation(SPD), the grain refinement of a Mg-9Gd-3Y-2Zn-0.5Zr alloy treated with decreasing temperature reciprocating upsetting-extrusion(RUE) and its influence on ...Based on the deforming technique of severe plastic deformation(SPD), the grain refinement of a Mg-9Gd-3Y-2Zn-0.5Zr alloy treated with decreasing temperature reciprocating upsetting-extrusion(RUE) and its influence on the mechanical properties and wear behavior of the alloy were studied. The RUE process was carried out for 4 passes in total, starting at 0 ℃ and decreasing by 10 ℃ for each pass. The results showed that as the number of RUE passes increased, the grain refinement effect was obvious, and the second phase in the alloy was evenly distributed. Room temperature tensile properties of the alloy and the deepening of the RUE degree showed a positive correlation trend, which was due to the grain refinement, uniform distribution of the second phase and texture weakening. And the microhardness of the alloy showed that the microhardness of RUE is the largest in 2 passes. The change in microhardness was the result of dynamic competition between the softening effect of DRX and the work hardening effect. In addition, the wear resistance of the alloy showed a positive correlation with the degree of RUE under low load conditions. When the applied load was higher, the wear resistance of the alloy treated with RUE decreased compared to the initial state alloy. This phenomenon was mainly due to the presence of oxidative wear on the surface of the alloy, which could balance the positive contribution of severe plastic deformation to wear resistance to a certain extent.展开更多
The sliding friction and wear behaviors of Mg-11Y-5Gd-2Zn-0.5Zr （wt%） alloy were investigated under oil lubricant condition by pin-on-disk configuration with a constant sliding distance of 1,000 m in the temperature...The sliding friction and wear behaviors of Mg-11Y-5Gd-2Zn-0.5Zr （wt%） alloy were investigated under oil lubricant condition by pin-on-disk configuration with a constant sliding distance of 1,000 m in the temperature range of 25-200℃. Results indicate that the volumetric wear rates and average friction coefficients decrease with the increase of sliding speeds, and increase with the increase of test temperature below 150℃. The hard and thermally stable Mg12（Y,Gd）Zn phase with long-period stacking order structure in the alloy presents significant wear resistance, The wear mechanism below 100℃ is abrasive wear as a result of plastic extrusion deformation. The corporate effects of severe abrasive, oxidative, and delaminating wear result in the tribological mechanism above 100℃.展开更多
Hot compression tests of Mg–11 Gd–4 Y–2 Zn–0.4 Zr alloy(GWZK114)were conducted at a deformation temperature range of 300–500°C and a strain rate range of 0.01–10.0 s-1.Based on systematic microstructure obs...Hot compression tests of Mg–11 Gd–4 Y–2 Zn–0.4 Zr alloy(GWZK114)were conducted at a deformation temperature range of 300–500°C and a strain rate range of 0.01–10.0 s-1.Based on systematic microstructure observation,it is confirmed that long period stacking ordered(LPSO)phase displays essential and evolving roles on the dynamic recrystallization(DRX)behavior.The results indicate that the plastic deformation is mainly coordinated by simultaneous exist of LPSO kinking of lamella 14 H-LPSO phase and DRX at 350–450℃,and DRX at 500℃.Further,it is found that the LPSO kinking induced during 350–450℃can delay the DRX.A phenomenological DRX model of GWZK114 alloy is established to be XDRX=1.exp[-0.5((ε-εc)/ε^*)0.91].Non-uniform distribution of plastic strain during compression was considered via finite element method and it ensures a good prediction of DRX fraction under a large plastic strain.Meanwhile,an enhanced DRX model,taking its formulation as XDRX={1.exp[-0.5((ε-εc)/ε*)0.91]}(T/(226.8)-1)n,n=3.82ε0.083,is proposed for the first time to capture the hindering effect of 14 H-LPSO kinking on DRX behavior.The predicted results of this enhanced DRX model agree well with the experimental cases,where 14 H-LPSO kinking is dominated or partially involved(300–450℃).Besides,a size model of DRX grains is also established and can depict the evolution of DRX grain size for all the investigated compression conditions with accounting for temperature rising at high strain rates(5 s^-1 and 10 s^-1).展开更多
文摘采用光学显微镜和蠕变实验机研究Mg-9Gd-4Y-1Zn-0.5Zr合金在不同温度和应力下的高温蠕变行为。结果表明：在应力为70～130 MPa范围内,200℃时Mg-9Gd-4Y-1Zn-0.5Zr合金的蠕变应力指数n=1.63,蠕变机制为晶界滑动,250℃时蠕变应力指数n=2.63,蠕变机制为位错滑移;在蠕变温度为200～250℃范围内,应力分别为70、90、110和130 MPa时,合金的蠕变激活能Qc分别为108.5、118.9、127.6和134.3 k J/mol;随着温度和应力的增加,合金晶粒长大,合金的蠕变机制由晶界滑动控制转变为位错滑移控制。
基金financially supported by the Natural Science Foundation of Shanxi Province (No. 201901D111176)the Joint Funds of the National Natural Science Foundation of china (Grant No. U20A20230)+3 种基金the Bureau of science, technology and industry for National Defense of China (No. WDZC2019JJ006)the Key R&D program of Shanxi Province (International Cooperation) (No. 201903D421036)the National Natural Science Foundation of China (Grant No. 52075501)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi (No. 2018002)。
文摘Based on the deforming technique of severe plastic deformation(SPD), the grain refinement of a Mg-9Gd-3Y-2Zn-0.5Zr alloy treated with decreasing temperature reciprocating upsetting-extrusion(RUE) and its influence on the mechanical properties and wear behavior of the alloy were studied. The RUE process was carried out for 4 passes in total, starting at 0 ℃ and decreasing by 10 ℃ for each pass. The results showed that as the number of RUE passes increased, the grain refinement effect was obvious, and the second phase in the alloy was evenly distributed. Room temperature tensile properties of the alloy and the deepening of the RUE degree showed a positive correlation trend, which was due to the grain refinement, uniform distribution of the second phase and texture weakening. And the microhardness of the alloy showed that the microhardness of RUE is the largest in 2 passes. The change in microhardness was the result of dynamic competition between the softening effect of DRX and the work hardening effect. In addition, the wear resistance of the alloy showed a positive correlation with the degree of RUE under low load conditions. When the applied load was higher, the wear resistance of the alloy treated with RUE decreased compared to the initial state alloy. This phenomenon was mainly due to the presence of oxidative wear on the surface of the alloy, which could balance the positive contribution of severe plastic deformation to wear resistance to a certain extent.
基金supported by the National Natural Science Foundation of China (No. 51074106)Key HiTech Research and Development Program of China (No. 2009AA033501)National Key Technology R&D Program of China (No. 2011BAE22B01-5)
文摘The sliding friction and wear behaviors of Mg-11Y-5Gd-2Zn-0.5Zr （wt%） alloy were investigated under oil lubricant condition by pin-on-disk configuration with a constant sliding distance of 1,000 m in the temperature range of 25-200℃. Results indicate that the volumetric wear rates and average friction coefficients decrease with the increase of sliding speeds, and increase with the increase of test temperature below 150℃. The hard and thermally stable Mg12（Y,Gd）Zn phase with long-period stacking order structure in the alloy presents significant wear resistance, The wear mechanism below 100℃ is abrasive wear as a result of plastic extrusion deformation. The corporate effects of severe abrasive, oxidative, and delaminating wear result in the tribological mechanism above 100℃.
文摘Hot compression tests of Mg–11 Gd–4 Y–2 Zn–0.4 Zr alloy(GWZK114)were conducted at a deformation temperature range of 300–500°C and a strain rate range of 0.01–10.0 s-1.Based on systematic microstructure observation,it is confirmed that long period stacking ordered(LPSO)phase displays essential and evolving roles on the dynamic recrystallization(DRX)behavior.The results indicate that the plastic deformation is mainly coordinated by simultaneous exist of LPSO kinking of lamella 14 H-LPSO phase and DRX at 350–450℃,and DRX at 500℃.Further,it is found that the LPSO kinking induced during 350–450℃can delay the DRX.A phenomenological DRX model of GWZK114 alloy is established to be XDRX=1.exp[-0.5((ε-εc)/ε^*)0.91].Non-uniform distribution of plastic strain during compression was considered via finite element method and it ensures a good prediction of DRX fraction under a large plastic strain.Meanwhile,an enhanced DRX model,taking its formulation as XDRX={1.exp[-0.5((ε-εc)/ε*)0.91]}(T/(226.8)-1)n,n=3.82ε0.083,is proposed for the first time to capture the hindering effect of 14 H-LPSO kinking on DRX behavior.The predicted results of this enhanced DRX model agree well with the experimental cases,where 14 H-LPSO kinking is dominated or partially involved(300–450℃).Besides,a size model of DRX grains is also established and can depict the evolution of DRX grain size for all the investigated compression conditions with accounting for temperature rising at high strain rates(5 s^-1 and 10 s^-1).
