Modifying microstructures and tensile properties of Mg-Sm based alloy via extrusion ratio

Microstructure and tensile properties of a Mg-Sm-Zn-Zr alloy with various extrusion ratios (ERs) of 6.9, 10.4 and 17.6 were systematically investigated. It was identified that, greater ER increased dynamic recrystallization (DRX) fraction and coarsened DRX grains, which further suggests weakened basal fiber texture for the studied alloy. This is mainly due to the rising temperature from massive deformation heat when hot-extrusion. As a result, greater ER corresponds to a decreased strength but improved ductility. Finally, transmission electron microscopy (TEM) observations reveal that the dominant intermetallic phase, Mg3Sm, is metastable, and it will transform into Mg41Sm5 during extrusion with high-ER. This transformation leads to the accumulation of surplus Sm and Zn atoms, which induces the precipitation of SmZn3 phase at the surface of Mg41Sm5 matrix.