Friction stir processing of thixoformed AZ91D magnesium alloy and fabrication of Al-rich surface  

作　　者：陈体军 朱战民 李元东 马颖 郝远 

机构地区：[1]State Key Laboratory of Gansu Advanced Nonferrous Materials, Lanzhou University of Technology

出　　处：《中国有色金属学会会刊：英文版》2010年第1期34-42,共9页Transactions of Nonferrous Metals Society of China

基　　金：Project(2007CB613706) supported by the National Basic Research Program of China;Project(3ZS042-B25-003) supported by the Natural Science Foundation of Gansu Province, China;Project(SKL03004) supported by the Development Program for Outstanding Young Teachers in Lanzhou University of Technology, China

摘　　要：The microstructural evolution characteristics of thermo-mechanically affected zone were investigated during friction stir processing (FSP) of the thixoformed AZ91D alloy. Simultaneously, an Al-rich surface layer was prepared by combination of Al powder using FSP method. The results indicate that the dynamic recrystallization and mechanical separation (including splitting and fracture of the primary grains) are the main mechanisms of grain refinement. For the thixoformed alloy, the operation efficiency of these mechanisms is less than that of the permanent mould casting AZ91D alloy, thus its microstructural evolution is relatively slow and the resulting grain size is relatively large. These are attributed to the differences in their original microstructures. The Al-rich surface layer can obviously improve the corrosion resistance in NaCl aqueous solution. A proper solution heat treatment (at 415 ℃ for 1 h) can further increase the corrosion resistance. In order to improve corrosion resistance, increasing the amount and improving the distribution uniformity of the Al-rich phase are more effective than increasing the Al solubility in the matrix.The microstructural evolution characteristics of thermo-mechanically affected zone were investigated during friction stir processing （FSP） of the thixoformed AZ91D alloy. Simultaneously, an Al-rich surface layer was prepared by combination of A1 powder using FSP method. The results indicate that the dynamic recrystallization and mechanical separation （including splitting and fracture of the primary grains） are the main mechanisms of grain refinement. For the thixoformed alloy, the operation efficiency of these mechanisms is less than that of the permanent mould casting AZ91D alloy, thus its microstructural evolution is relatively slow and the resulting grain size is relatively large. These are attributed to the differences in their original microstructures. The Al-rich surface layer can obviously improve the corrosion resistance in NaCl aqueous solution. A proper solution heat treatment （at 415 ℃ for 1 h） can further increase the corrosion resistance. In order to improve corrosion resistance, increasing the amount and improving the distribution uniformity of the Al-rich phase are more effective than increasing the A1 solubility in the matrix.

关 键 词：AZ91D镁合金 表面加工 触变成形 富铝相 摩擦 搅拌 耐腐蚀性能 NACL水溶液 

分 类 号：TG146.22[一般工业技术—材料科学与工程] TG142.71[金属学及工艺—金属材料]