等通道转角挤压对ZM61镁合金组织与性能的影响

Effect of equal channel angular pressing on the microstructure and mechanical properties of ZM61 magnesium alloy

以ZM61镁合金为研究对象,在350℃下,采用Bc路径对ZM61镁合金进行了4道次的等通道转角挤压(ECAP),研究了挤压道次对ZM61镁合金的第二相、微观结构及力学性能的影响.结果表明:4道次ECAP处理后,晶界上连续网状Mg-Zn相被剪切成颗粒状弥散分布在基体组织中,合金的平均晶粒尺寸由200μm减小到20μm,晶粒尺寸较为均匀,主要原因是形变诱导引发的晶粒破碎和挤压过程中发生的动态再结晶现象;挤压过程中,晶粒取向发生改变,织构由原来基面的随机织构转变成ECAP变形后的剪切织构;同时,ECAP可显著提高ZM61镁合金的力学性能,细晶强化是其中主要的强化机制,挤压4道次后合金的极限抗拉强度、伸长率较原始状态分别提高了110%和486%;ECAP处理后合金的拉伸断裂方式由脆性断裂转变为混合断裂.

In this paper,ZM61 magnesium alloy was taken as the research object.The ZM61 magnesium alloy was subjected to four passes of equal channel angular pressing(ECAP)with Bc path at 350℃,and the effects of extrusion passes on the second phase,microstructure and mechanical properties of ZM61 magnesium alloy were studied.The results show that after four ECAP passes,the Mg-Zn phases in the grain boundary are shear into granular and disperse in the matrix.The average grain size of the alloy decreases from 200μm to 20μm,and the grain size is relatively uniform,which is mainly due to the dynamic recrystallization during the process of grain fragmentation and extrusion induced by deformation;During the extrusion process,the grain orientation changes and the texture changes from the random texture of the original base plane to the shear texture after ECAP deformed.At the same time,ECAP can significantly improve the mechanical properties of ZM61 alloy,and fine-grain strengthening is the main strengthening mechanism.After four passes of extrusion,the ultimate tensile strength and elongation of the alloy are increased by 110%and 486%compared with the initial state,respectively;After ECAP treatment,the tensile fracture mode of the alloy changed from brittle fracture to mixed fracture.