Role of extrusion temperature on the microstructure evolution and tensile properties of an ultralight Mg-Li-Zn-Er alloy

Role of extrusion temperature on the microstructure evolution and tensile properties of an ultralight Mg10Li-5Zn-0.5Er alloy was studied. The results indicate that the second phases and grains are all refined after extrusion. It is firstly reported that there are two kinds of grains zone including micro-grained region and coarse-grained region in the as-extruded Mg-Li alloys with high Li content (>_ 9 wt%). As the extrusion temperature increases from 150 degrees C to 300 degrees C, the volume of micro-grained region decreases and finally almost disappears. The grain size of coarse-grained region increases as well. The amount of Mg-Li-Zn precipitates along the boundaries decreases and their quantity in the grains increases with grain coarsening. The strength rises slightly and the elongation decreases notably with the enhancement of extrusion temperature. As the extrusion temperature increases, the crack initiation appears from mainly around the bulky Mg-Zn-Er phases to mainly along the grain boundaries. Due to the grain refinement, the second phases strengthening, and the abundant slip systems of beta-Li phase, the comprehensive properties of the as -extruded alloys have leading position in the field of wrought Mg-Li alloys and the optimum comprehensive tensile properties are gained in the alloy extruded at 275 degrees C. (c) 2021 Published by Elsevier B.V.