The biomagnesium alloys have been considered to be one of the most potential biodegradable metal materials due to its good mechanical compatibility, biological compatibility, biological security and biodegradable char...The biomagnesium alloys have been considered to be one of the most potential biodegradable metal materials due to its good mechanical compatibility, biological compatibility, biological security and biodegradable characteristics. However, the two major problems of high degradation rates in physiological environment and low mechanical properties prevent the development of biomagnesium alloys. In the present work, the samples of Mg-Zn-Y-Nd alloy were prepared by cyclic extrusion compression （CEC） and equal channel angular pressing （ECAP）. The microstructures, mechanical properties of alloy and its corrosion behavior in simulated body fluid （SBF） were evaluated. The results reveal that Mg-Zn-Y-Nd alloy consists of equiaxial fine grain structure with the homogeneous distribution of micrometer size and nano-sized second phase, which was caused by the dynamic recrystallization during the ECAP and CEC. The corrosion resistance of alloy was improved. The tensile and corrosion resistance were improved, especially the processed alloy exhibit uniform corrosion performances and decreased corrosion rate. This will provide theoretical ground for Mg-Zn-Y-Nd alloy as vascular stent application.展开更多
The effects of CEC passes, isothermal holding time and reheating temperature on the microstructure evolution and grain coarsening behaviour of AZ61 magnesium alloy produced by the recrystallisation and partialmelting ...The effects of CEC passes, isothermal holding time and reheating temperature on the microstructure evolution and grain coarsening behaviour of AZ61 magnesium alloy produced by the recrystallisation and partialmelting （RAP） process were investigated. Before partial remelting, as-cast AZ61 alloy was deformed by cyclic extrusion compression （CEC） with one pass and two pass at 330 ℃. After CEC, the microstructure consisted of unrecrystallized grains and deformed eutectic compounds. Increasing isothermal holding time resulted in the formation of spheroidal grains surrounded by liquid films. With increasing the isothermal holding time, the solid grain size increased and the degree of spheroidization was improved. With increasing the reheating temperature, namely increasing liquid fraction, the solid grain size obviously decreased during the period from 560 ℃ to 570 ℃ and then slightly increased after 570 ℃, while the shape factor increased monotonously. During partial remelting, increasing reheating temperature can properly short the isothermal holding time to obtain fine structure. Moreover, increasing the numbers of CEC passes could produce finer semi-solid microstructure. The coarsening behavior of solid grains in the semi-solid state obeys Ostwald ripening and grain coalescence mechanisms. The coarsening rate constant, K, 595 ℃. After CEC plus partial remelting, the ideal and fine was suitable for thixoforming. was 80μm^3.s^-1 for samples partially remelted at semi-solid state structure can be obtained, which展开更多
The cyclic extrusion compression （CEC） was applied to severely deform the as-extruded GW102K （Mg- 10.0Gd-2.0Y-0.5Zr, wt%） alloy at 350, 400, and 450 ℃, respectively. The microstructure, texture, and grain boundar...The cyclic extrusion compression （CEC） was applied to severely deform the as-extruded GW102K （Mg- 10.0Gd-2.0Y-0.5Zr, wt%） alloy at 350, 400, and 450 ℃, respectively. The microstructure, texture, and grain boundary character distribution of the CECed alloy were investigated in the present work. The mechan- ical properties were measured by uniaxial tension at room temperature. The crack initiation on the longitudinal section near the tensile fracture-surface was investigated by high-resolution scanning elec- tron microscopy （SEM）. The result shows that the microstructure was dramatically refined by dynamic recrystallization （DRX）. The initial fiber texture was disintegrated and obviously weakened. The 8-passes/ 350 ℃ CECed alloy exhibited yield strength of 318 MPa with an elongation-to-fracture of 16.8%, increased by 41.3% and 162.5%, respectively. Moreover, the elongation-to-fracture of the 8-passes/450 ℃ CECed alloy significantly increased more than 3 times than that of the received alloy. The cracks were mainly initi- ated at twin boundaries and second phase/matrix interfaces during tensile deformation. The microstructure refinement was considered to result in the dramatically enhanced of the strength and ductility. In ad- dition, the texture randomization during CEC is beneficial for enhancing ductility. The standard positive Hall-Petch relationships have been obtained for the CECed GW102K alloy.展开更多
Microstructure evolution of ZK60 magnesium alloy deformed at 623 K by cyclic extrusion compression (CEC) large deformation method was investigated. ZK60 alloy was deformed in the range of accumulated true strain of 0....Microstructure evolution of ZK60 magnesium alloy deformed at 623 K by cyclic extrusion compression (CEC) large deformation method was investigated. ZK60 alloy was deformed in the range of accumulated true strain of 0.8-17. The microstructure of evolution was investigated by optical microscope (OM) and transmission electron microscopy (TEM). The results show that microstructure is obviously refined, and homogenous equiaxed microstructure is achieved in the entire range of the examined deformations by subjected to CEC deformation. By increasing the accumulated strain to 17, the grain size decreases into sub-micron regime with about several hundred nanometers. The mechanism of grain refinement in ZK60 alloy by CEC can be attributed to continuous dynamic recovery and recrystallization.展开更多
基金Acknowledgements The authors are grateful for the support by National Key Technology R＆D Program of China （Grant No. 2012BAI18B01） and the National Natural Science Foundation of China （Grant No. 51171174）.
文摘The biomagnesium alloys have been considered to be one of the most potential biodegradable metal materials due to its good mechanical compatibility, biological compatibility, biological security and biodegradable characteristics. However, the two major problems of high degradation rates in physiological environment and low mechanical properties prevent the development of biomagnesium alloys. In the present work, the samples of Mg-Zn-Y-Nd alloy were prepared by cyclic extrusion compression （CEC） and equal channel angular pressing （ECAP）. The microstructures, mechanical properties of alloy and its corrosion behavior in simulated body fluid （SBF） were evaluated. The results reveal that Mg-Zn-Y-Nd alloy consists of equiaxial fine grain structure with the homogeneous distribution of micrometer size and nano-sized second phase, which was caused by the dynamic recrystallization during the ECAP and CEC. The corrosion resistance of alloy was improved. The tensile and corrosion resistance were improved, especially the processed alloy exhibit uniform corrosion performances and decreased corrosion rate. This will provide theoretical ground for Mg-Zn-Y-Nd alloy as vascular stent application.
文摘The effects of CEC passes, isothermal holding time and reheating temperature on the microstructure evolution and grain coarsening behaviour of AZ61 magnesium alloy produced by the recrystallisation and partialmelting （RAP） process were investigated. Before partial remelting, as-cast AZ61 alloy was deformed by cyclic extrusion compression （CEC） with one pass and two pass at 330 ℃. After CEC, the microstructure consisted of unrecrystallized grains and deformed eutectic compounds. Increasing isothermal holding time resulted in the formation of spheroidal grains surrounded by liquid films. With increasing the isothermal holding time, the solid grain size increased and the degree of spheroidization was improved. With increasing the reheating temperature, namely increasing liquid fraction, the solid grain size obviously decreased during the period from 560 ℃ to 570 ℃ and then slightly increased after 570 ℃, while the shape factor increased monotonously. During partial remelting, increasing reheating temperature can properly short the isothermal holding time to obtain fine structure. Moreover, increasing the numbers of CEC passes could produce finer semi-solid microstructure. The coarsening behavior of solid grains in the semi-solid state obeys Ostwald ripening and grain coalescence mechanisms. The coarsening rate constant, K, 595 ℃. After CEC plus partial remelting, the ideal and fine was suitable for thixoforming. was 80μm^3.s^-1 for samples partially remelted at semi-solid state structure can be obtained, which
基金Project (12511069) supported by Department of Education of Heilongjiang Province, ChinaProject (201210214008) supported by Training Programs of Innovation and Entrepreneurship for Undergraduates, China
基金supported by the National Natural Science Foundation of China (No. 51204117)Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxithe Natural Science Foundation of Shanxi province (No. 2015021017)
文摘The cyclic extrusion compression （CEC） was applied to severely deform the as-extruded GW102K （Mg- 10.0Gd-2.0Y-0.5Zr, wt%） alloy at 350, 400, and 450 ℃, respectively. The microstructure, texture, and grain boundary character distribution of the CECed alloy were investigated in the present work. The mechan- ical properties were measured by uniaxial tension at room temperature. The crack initiation on the longitudinal section near the tensile fracture-surface was investigated by high-resolution scanning elec- tron microscopy （SEM）. The result shows that the microstructure was dramatically refined by dynamic recrystallization （DRX）. The initial fiber texture was disintegrated and obviously weakened. The 8-passes/ 350 ℃ CECed alloy exhibited yield strength of 318 MPa with an elongation-to-fracture of 16.8%, increased by 41.3% and 162.5%, respectively. Moreover, the elongation-to-fracture of the 8-passes/450 ℃ CECed alloy significantly increased more than 3 times than that of the received alloy. The cracks were mainly initi- ated at twin boundaries and second phase/matrix interfaces during tensile deformation. The microstructure refinement was considered to result in the dramatically enhanced of the strength and ductility. In ad- dition, the texture randomization during CEC is beneficial for enhancing ductility. The standard positive Hall-Petch relationships have been obtained for the CECed GW102K alloy.
基金Project (50674067) supported by the National Natural Science Foundation of China
文摘Microstructure evolution of ZK60 magnesium alloy deformed at 623 K by cyclic extrusion compression (CEC) large deformation method was investigated. ZK60 alloy was deformed in the range of accumulated true strain of 0.8-17. The microstructure of evolution was investigated by optical microscope (OM) and transmission electron microscopy (TEM). The results show that microstructure is obviously refined, and homogenous equiaxed microstructure is achieved in the entire range of the examined deformations by subjected to CEC deformation. By increasing the accumulated strain to 17, the grain size decreases into sub-micron regime with about several hundred nanometers. The mechanism of grain refinement in ZK60 alloy by CEC can be attributed to continuous dynamic recovery and recrystallization.
