往复挤压对挤压态ZK60镁合金微观组织和力学性能的影响

Effect of cyclic extrusion and compression on microstructure and mechanical properties of extruded ZK60 magnesium alloy

在350℃下,对挤压态ZK60镁合金分别进行1、4、8道次的往复挤压变形(CEC)。利用金相显微镜(OM)、透射电镜(TEM)观察往复挤压前后ZK60镁合金的微观组织,利用X射线衍射仪(XRD)分析变形前后晶面取向变化,在万能拉伸试验机上测试变形前后镁合金的力学性能,并利用扫描电镜(SEM)观察拉伸断口形貌。往复挤压后的检测结果表明,挤压态ZK60镁合金晶粒显著细化,晶粒尺寸分布较均匀,随着挤压道次增多,晶粒尺寸逐渐减小;1道次变形后组织内产生了大量晶格缺陷,出现了大角度晶界,第二相粒子分布在晶粒内部和晶界上;各晶面衍射峰增强,拉伸断口内存在大量基体撕裂棱和明显的韧窝分布;ZK60镁合金的力学性能变化较大,随着挤压道次增多,伸长率大幅提高,抗拉强度小幅增大,而屈服强度降低。

ZK60 magnesium alloy was deformed by cyclic extrusion compression （CEC） with one pass, tour passes and eight passes at 350 ℃, respectively. The microstructure of ZK60 magnesium alloy was studied by optical microscope （ OM ） and transmission electron microscope （TEM）, X-ray diffraction （XRD） was used to analyze the ZK60 variation of orientation of crystal plaue before and after CEC, the mechanical properties before and after CEC were studied by universal testing machine and tensile fracture was observed by scanning elec- tron microscope （SEM）. Results show that ZK60 magnesium alloy grains are refined markedly after CEC and grain size distribution is more uniform, the grain size decreases with the increase of the number of extrusion passes. After one pass deformation, there are a large number of lattice defects, and large angle grain boundary appears, and the second phase particles are distributed in the grain interior and grain boundaries. After CEC, crystal diffraction peak increases, and there are a large amount of matrix tearing edge and obvious fracture dimples in the tensile fracture surface. The mechanical properties of ZK60 magnesium alloy are greatly changed after CEC, and with the increase of the extrusion pass, the elongation is greatly improved, the tensile strength is slightly improved, the yield strength decreases cantinnously.