铸态Mg_(96)Zn_3Y_1合金高温热处理显微结构的电子显微研究  

Electron microscopy study of microstructural variations for the as-cast Mg_(96)Zn_3Y_1 alloy subjected to high-temperature heat treatment

作　　者：薛大帅[1] 刘林林[1] 孙威[1] 

机构地区：[1]北京工业大学固体微结构与性能研究所,北京100124

出　　处：《电子显微学报》2011年第6期488-493,共6页Journal of Chinese Electron Microscopy Society

基　　金：北京市自然科学基金资助项目(No.2092005);教育部博士点基金项目(20091103110019)

摘　　要：本文应用扫描背散射电子(SEM-BSE)像和透射电子显微(TEM)像观察的方法,研究了铸态Mg96 Zn3Y1(at.%)合金经过500℃高温热处理后显微组织结构的变化。结果表明铸态Mg96 Zn3Y1(at.%)合金中的初生相为网格状形貌,其中多数为面心立方W(Mg3Zn3Y2)相,少数为二十面体准晶I(Mg3Zn6Y)相。经过500℃+4h高温热处理后,初生相整体网格状形貌不发生明显的变化,但准晶I相消失。同时,Mg基体中析出大量弥散分布的具有面心立方结构的片状W’相,高分辨电子显微(HREM)像表明W’相沿基体(001)Mg面以台阶方式生长,并与Mg基体具有半共格界面关系。取向关系满足:[233]W’∥[110]Mg,(311)W’∥(110)Mg,(022)W’∥(001)Mg。SEM-BSE,TEM and HREM observations have been carried out to characterize the microstructural variations for the as-cast Mg96Zn3Y1（at.%） alloys subjected to high-temperature heat treatment at 500℃.The results show that the characteristic network structure formed in the as-cast Mg96Zn3Y1 alloy is constructed with most primary W-phase（fcc,Mg3Y2Zn3 type） and a small amount of coexisting icosahedral quasicrystal phase（I-phase）.After heat treated at 500℃ for 4 h,the network structure retained without apparent morphological variation even through the I-phase melted down and disappeared.In addition,a large number of platelet-shaped fcc W＇-phases were observed to precipitate in the matrix due to the heat treatment,and relative increase of Zn-concentration in the Mg matrix was also detected.These variations are responsible for the significant hardness enhancement of the heat-treated alloy.HREM observations indicate a ledge growth mechanism for the platelet-shaped W＇-phase whose interface exhibits a semi-coherent relationship with the Mg-matrix.The orientational relationships between the W＇ precipitate phase and the Mg-matrix have been determined to be as follows： W＇∥Mg,（311）W＇∥（110）Mg,（022）W＇∥（001）Mg.

关 键 词：MG-ZN-Y合金 显微结构 热处理 析出相 电子显微技术 

分 类 号：TG115.215.3[金属学及工艺—物理冶金] TG146.22[金属学及工艺—金属学]