AZ31镁合金连续变断面挤压变形行为及组织演变

Deformation Behavior and Microstructure Evolution of AZ31 Magnesium Alloy by Extrusion with Continuous Variation in Crosssection

采用大变形量的连续变断面循环挤压工艺对铸态AZ31镁合金进行不同道次的挤压变形,分析了其在变形到断裂过程中的受力情况和微观组织变化。研究表明:随着变形次数的增加,铸态AZ31镁合金晶粒不断被细化,10道次变形后,晶体内的不均匀变形被消除,粗大的晶粒全部变为细小的等轴晶,晶界上的第二相和杂质也均匀地分布在晶粒间;变形过程中发生了动态再结晶,原始粗大晶粒在形成细小等轴晶的同时仍能保持原有晶体位置的遗传性;变形过程中主要以孪晶为主,锥形裂纹末端为沿晶和穿晶结合型断裂,侧面为单一型穿晶断裂,并且裂纹两边显微组织存在较大差异性。

Extrusion deformation was carried out for AZ31 magnesium alloy for different times with continuous varying cross-section extrusion technology.The force condition and microstructure were analyzed during the deformation up to breakage.The results show that the crystal grains of the materials are constantly refined with deformation times.After being pressed for 10 times,inhomogeneous deformation is eliminated and the coarse grains are all turned into fine equiaxed grains.Impurities and second phases are also distributed in the grain boundaries;Dynamic recrystallization occur during deformation and the original coarse grains can keep the heredity of the original crystal position while forming fine equiaxed grains insidw;Deformation process is mainly based on twin,the end of the conical crack is the combine of intergranular fracture and transgranular fracture.Side of crack is single transgranular fracture and there is a big difference between the two sides of the crack.