高塑性Mg-3Zn-1Y-1Mn合金在不同挤压温度下的组织演变、强化机制和变形行为

Microstructure evolution,strengthening mechanisms and deformation behavior of high-ductility Mg-3Zn-1Y-1Mn alloy at different extrusion temperatures

为了改善铸态Mg-3Zn-1Y-1Mn合金的力学性能、研究合金在不同变形温度下的组织演变规律和变形机理,对铸态Mg-3Zn-1Y-1Mn合金进行热挤压实验。实验结果显示,当挤压温度为330℃时,挤压态合金具有最佳的力学性能,抗拉强度和伸长率分别达到270 MPa和16.8%。挤压态合金性能大幅提高主要归因于3个方面:由动态再结晶导致的细晶强化作用、未被动态再结晶抵消的加工硬化以及第二相粒子强化作用。在热挤压过程中,当挤压温度为300℃时,同时发生连续动态再结晶和动态回复;而当挤压温度为330和360℃时,发生不连续动态再结晶。此外,在热变形过程中{0001}基面滑移、{10 10}Ⅰ型柱面滑移和{11 20}Ⅱ型柱面滑移对塑性变形的贡献受挤压温度影响很大,而{11 20}Ⅱ型柱面是3个滑移系中最难启动的滑移系。

Hot extrusion was performed on as-cast Mg-3Zn-1Y-1Mn alloy to further improve the mechanical properties and investigate its microstructure evolution and deformation mechanism at different thermal deformation temperatures.The experimental results suggested that the alloy at the extrusion temperature of 330°C had the optimal mechanical properties,and the tensile strength and elongation of the alloy were 270 MPa and 16.8%,respectively.The strength improvement of the as-extruded alloy primarily arose from three aspects,including fine-grain strengthening due to dynamic re-crystallization(DRX),dislocation strengthening not offset by DRX,and second phase strengthening.Continuous dynamic re-crystallization(CDRX)and dynamic recovery(DRV)occurred simultaneously at the extrusion temperature of 300°C.The discontinuous dynamic re-crystallization(DDRX)occurred at the extrusion temperature of 330 and 360°C.However,the contribution of{0001}basal plane slip,{10 10}prismatic type I and{11 20}prismatic typeⅡslips to plastic deformation was significantly affected by the extrusion temperature.The{11 20}prismatic typeⅡslip was found to be the most difficult one to initiate among the three slip systems.