关键词: Mg-8Al-3.5Sr镁合金, 晶粒细化, 热轧, 再结晶退火, 显微结构

Abstract: At present,basic research on the plastic deformation of the heat-resistant magnesium alloy and the subsquent heat treatment process is relatively little. However,they are the bottleneck of the magnesium industry. Therefore,the as-cast Mg-8Al-3.5Sr magnesium alloy was subjected to solution treatment,and then hot rolling and recrystallization annealing. The microstructure of the samples before and after annealing was studied by optical microscope and scanning electron microscope. The results show that the rod-like Al₄Sr phase is appeared,and the grain boundaries become clearly visible as polygonal with an average grain size of 65μm,when the alloy sample was treated by solution at 380℃ for 24h. With the increase of hot rolling reduction,the average grain size decreased,and the optimum microstructure which had an average grain size of 26μm was obtained when the hot rolling reduction was 80%. When the reduction amount was increased to 90%,there were a large number of cracks. When the recrystallization annealing condition was 300℃ for 1h,the equiaxed recrystallization structure appeared in the crystal,and the average grain size was further reduced to 21.5μm. When the recrystallization annealing temperature was too high,the grains would grow abnormally and the Mg₁₇Al₁₂ phase precipitated.

Key words: Mg-8Al-3.5Sr alloy, grain refinement, hot rolling, recrystallization annealing, microstructure