(西安理工大學(xué) 材料科學(xué)與工程學(xué)院，西安 710048)
摘 要: 研究了擠壓態(tài)AZ91鎂合金的SIMA法半固態(tài)組織演變。 結(jié)果表明： 擠壓合金為以α-Mg再結(jié)晶等軸晶為主相， 與極少量細(xì)粒狀成串分布于α-Mg基體上的Mg17Al12顆粒組成的兩相組織，基體中存在大量的大角度亞晶及高密度的位錯纏結(jié)。 在二次加熱過程中， 原子擴(kuò)散通道多， 晶界液化及顆粒球化所需的加熱溫度低，等溫時間短。 565 °C等溫5 min,即可獲得固相率為57%， 顆粒平均直徑為58 μm、 形狀圓整、 分布均勻的半固態(tài)組織。 等溫5 min后， 半固態(tài)顆粒發(fā)生長大， 其長大機(jī)制為Ostwald熟化。
關(guān)鍵字: 鎂合金； SIMA法半固態(tài)； 固相粒化； 組織演變
（ 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
