Microstructure evolution and texture development in thermomechanically processed Mg-Li-Al based alloys

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• 作者：Vinod Kumar^a ; ¹ ; Govind^b ; Rajiv Shekhar^a ; R. Balasubramaniam^a ; ² ; Kantesh Balani^a ; ^{kbalani@iitk.ac.in}
• 关键词：Mg&ndash ; Li&ndash ; Al based alloy ; Thermomechanical processing ; EBSD ; Recrystallization ; Microanalysis ; Precipitation
• 刊名：Materials Science and Engineering ; A
• 出版年：2012
• 期刊代码：61_09215093
• 类别：ms
• 出版时间：15 June, 2012
• 卷：547
• 期：Complete
• 页码：38-50
• 文件大小：4162 K

摘要

In the present study, the influence of alloying and thermomechanical processing on the microstructure and texture evolution on the two Mg-Li-Al based alloys, namely Mg-9 wt%Li-7 wt%Al-1 wt%Sn (LAT971) and Mg-9 wt%Li-5 wt%Al-3 wt%Sn-1 wt%Zn (LATZ9531) has been elicited. Novel Mg-Li-Al based alloys were cast (induction melting under protective atmosphere) followed by hot rolling at 鈭?73 K with a cumulative reduction of five. A contrary dual phase dendritic microstructure rich in 伪-Mg, instead of 尾-Li phase predicted by equilibrium phase diagram of Mg-Li binary alloy was observed. Preferential presence of Mg-Li-Sn primary precipitates (size 4-10 渭m) within 伪-Mg phase and Mg-Li-Al secondary precipitates (<3 渭m) interspersed in 尾-Li indicated their degree of dissolution during hot-rolling and homogenization in the dual phase matrix. Presence of Al, Sn and Zn alloying elements in the Mg-Li based alloy has resulted an unusual dual-phase microstructure, change in the lattice parameter, and intriguing texture evolution after hot-rolling of cast LAT 971 and LATZ9531 alloy. Strong texture was absent in the as-cast samples whereas texture development after hot-rolling revealed an increased activity of the non-basal slip planes. The quantification of the grain average misorientation (less than 2掳) using electron backscattered diffraction confirmed the presence of strain free grains in majority of the grains (fraction >0.75) after hot-rolling of Mg-Li-Al based alloys. Role of alloying in rendering distribution of dual-phase structure has strongly influenced dynamic-recrystallization and grain-growth in the hot-rolled Mg-Li-Al based alloys.