高压压铸Mg-4Al-0．4Mn-xPr镁合金的显微组织和力学性能

Microstructures and mechanical properties of high-pressure die-cast Mg-4Al-0.4Mn-xPr alloys

采用高压压铸方法制备了Mg-4Al-0.4Mn-xPr(x=0,1,2,4,6,质量分数,%)系列镁合金,利用X射线衍射仪、场发射环境扫描电子显微镜、显微硬度测试、拉伸和压缩性能测试以及断口分析等手段研究了Pr对高压压铸Mg-4Al基合金微观组织和力学性能的影响。结果表明:高硬度合金铸造表面层与表面层中的高Pr含量和细密的组织有关;随着Pr添加量的增加,Al2Pr和Al11Pr3相在晶界附近形成,且其相对比例随之变化,同时合金组织被明显细化;添加约4%Pr(质量分数)的合金具有最佳的力学性能,良好的力学性能从室温一直保持到200℃;合金力学性能的提高主要由于合金致密的铸造表面层、大量第二相聚集晶界带来的晶界强化和细晶强化以及固溶强化所致。

Mg-4Al-0.4Mn-xPr （x=0, 1, 2, 4 and 6, mass fraction, %） magnesium alloys were prepared by high-pressure die-casting technique. The effect of Pr on the microstructures and mechanical properties of die-cast Mg-4Al based alloy were investigated by XRD, FESEM, microhardness test, tensile and compressive properties tests and analysis of fracture surface. The results show that the fine rigid skin region is related to the aggregation of Pr and fine microstructure. Al2Pr and Al11Pr3 phases are mainly concentrated along the grain boundaries, and the relative ratio of the above two phases is in correlation with the Pr content in the alloy. Meanwhile, the grain sizes are greatly reduced with increasing Pr content. The mass fraction of Pr around 4% is considered to be suitable to obtain the optimal mechanical properties those can keep well until 200 ℃. The outstanding mechanical properties are mainly resulted from the rigid casting surface layer, grain boundary strengthening obtained by an amount of precipitates, grain refinement strengthening, as well as solid solution strengthening.