(西安理工大学 材料科学与工程学院，西安 710048)
摘 要: 研究了挤压态AZ91镁合金的SIMA法半固态组织演变。 结果表明： 挤压合金为以α-Mg再结晶等轴晶为主相， 与极少量细粒状成串分布于α-Mg基体上的Mg17Al12颗粒组成的两相组织，基体中存在大量的大角度亚晶及高密度的位错缠结。 在二次加热过程中， 原子扩散通道多， 晶界液化及颗粒球化所需的加热温度低，等温时间短。 565 °C等温5 min,即可获得固相率为57%， 颗粒平均直径为58 μm、 形状圆整、 分布均匀的半固态组织。 等温5 min后， 半固态颗粒发生长大， 其长大机制为Ostwald熟化。
关键字: 镁合金； SIMA法半固态； 固相粒化； 组织演变
（ School of Materials Science and Engineering,
Xi'an University of Technology, Xi'an 710048, China）
Abstract: The microstructural evolution of semisolid AZ91 magnesium alloy by SIMA process was investigated. The microstructure of as-extruded Mg alloy is mainly composed of α-Mg recrystallized grains and a small quantity of Mg17Al12 particles distributed in Mg matrix as a cluster. There are a great deal of large angle subcrystals and high density dislocations in α-Mg grains. Due to many of atom diffusion channels during secondary heating, the heating temperature required for liquidizing of grain boundaries and spheroidizing of grain surfaces is low and the holding time becomes short. Holding 5 min at 565 °C, the homogeneous semisolid microstructure with solid fraction of 57% and mean grain size of about 58 μm is obtained. After holding 5 min, the semisolid grains become coarse and the coarsening mechanism is Ostwald ripening.
Key words: magnesium alloy; SIMA semisolid; granulating; microstructural evolution
