AZ91D镁合金表面强变形微观结构研究

Investigation on Microstructure of AZ91D Magnesium Alloy by Surface Severe Deformation

首先对铸态AZ91D镁合金进行固溶处理,然后通过直径φ6mm、φ10mm和φ20mm的钢球对其进行表面机械研磨强变形处理.采用光学显微镜(OM)、透射电镜(TEM)以及高分辨透射电镜(HRTEM)等表征了AZ91D镁合金表面强变形微观结构.结果表明:表面机械研磨处理后,AZ91D镁合金组织发生明显变化,表层最细晶粒尺寸可达20 nm,变形层组织呈梯度变化,钢球直径对表层机械研磨处理试样组织影响明显,小径钢球晶粒细化效果不明显,大径钢球则不能覆盖整个处理表面.

Firstly,as cast AZ91D magnesium alloy was annealed by solid solution and then severe plastic deformed by surface mechanical attrition treatment（ SMAT） with steel balls with diameter of φ6mm,φ10mm and φ20mm. The surface severe plastic deformed microstructure was investigated by optical microscopy（ OM）,transmission electronic microscopy（ TEM） and high- resolution transmission electronic microscopy（ HRTEM） etc. The results show that the microstructure of AZ91D magnesium alloy processed by surface mechanical attrition changed obviously,and which was in gradient distribution. The surface grains size reached about 20nm,and the diameter of steel balls has great effect on the microstructure of SMATed samples. The grain refinement effect of small balls are not obvious,however the large ones could not cover the whole treated surface.