Effects of Li addition on the microstructure and tensile properties of the extruded Mg-1Zn-xLi alloy

Li addition is verified to be an effective method to increase the room temperature ductility and formability of Mg alloys. In the present study, the microstructure, texture, and tensile properties of the extruded Mg-1Zn-xLi (wt%, x = 0, 1, 3, 5) alloy sheets were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), and electron backscatter diffraction (EBSD). It was found that Li addition resulted in the grain coarsening and the development of new transverse direction (TD)-tilting and 〈101¯0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$10\bar{1}0$$\end{document}〉 parallel to extrusion direction textures, which was related to the improved dynamic recrystallization and the increased prismatic slip during extrusion. The Mg-1Zn−5Li sheet showed the weakest texture, which contained both basal and TD-tilting oriented grains. No additional phase was formed with Li addition. The yield strength of Mg-1Zn-xLi sheets gradually decreased with increasing Li content, which was mainly related to the grain coarsening and texture weakening. In addition, the ductility of the Mg-1Zn-xLi sheet was remarkably enhanced by Li addition. The elongation of the Mg-1Zn-5Li sheet was 30.3% along the TD, which was three times than that of Mg-1Zn sheet. Microstructural analysis implied that this significant ductility enhancement was associated with the improvement activation of prismatic and basal slips during the tensile tests. This study may provide insights into the development of high-ductility, low-density Mg-Zn-Li based alloys.