Effects of Mg_(17)Al_(12) phase on microstructure evolution and ductility in the AZ91 magnesium alloy during the continuous rheo-squeeze casting-extrusion process  

作　　者：Dijia Zhao Shulin Lü Wenbo Guo Shilong Li Jianyu Li Guanghui Guo Wei Guo Shusen Wu 

机构地区：[1]State Key Laboratory of Materials Processing and Die&Mould Technology,School of Materials Science and Engineering,Huazhong University of Science and Technology,Wuhan 430074,China

出　　处：《Journal of Materials Science & Technology》2024年第24期63-79,共17页材料科学技术(英文版)

基　　金：funded by the National Natural Science Foundation of China(No.52175321).

摘　　要：In this study,a high-ductility AZ91 magnesium alloy was fabricated by the novel continuous rheo-squeeze casting-extrusion(CRSCE)process.The semi-solid slurry was prepared by ultrasonic vibration(UV)treatment,then solidified under pressure,and finally hot extruded.UV treatment can reduce the Al element content in primary grains and increase it in secondary grains.The refined Mg_(17)Al_(12) phase was scattered along secondary grain boundaries and then stretched into narrow,fibrous bands during the hot extrusion.The fibrous bands with proper separation distances can accelerate the dynamic recrystallization(DRX)process and suppress the growth of DRXed grains.Microcracks were initiated inside the brittle Mg_(17)Al_(12) phase and tended to propagate along the continuously distributed Mg_(17)Al_(12) phase during the tensile test.Thus,the tiny Mg_(17)Al_(12) phase in the billet and narrow,fibrous bands in as-extruded rods can prevent cracks from spreading and enhance ductility.Therefore,excellent comprehensive mechanical properties were obtained,with an ultimate tensile strength of 326.3 MPa and an elongation of 16.46%.The CRSCE method offers a novel way to fabricate high-ductility and high-alloyed magnesium alloys without homogenization.Microstructure regulation mechanisms of CRSCE,microstructural hereditary laws,and the effect of the Mg_(17)Al_(12) phase on mechanical properties were further discussed.

关 键 词：AZ91 magnesium alloy Mg_(17)Al_(12)phase Rheo-squeeze casting Ultrasonic vibration Continuous casting-extrusion DUCTILITY 

分 类 号：TG146.22[一般工业技术—材料科学与工程]