Microstructure and mechanical properties of Mg-Gd-Y-Zn-Mn alloy sheets processed by large-strain high-efficiency rolling

摘要

The high-performance Mg-8.8Gd-3.4Y-1Zn-0.8Mn (wt%) alloy sheets were prepared by large-strain high-efficiency rolling process. The large strains with similar to 87% and similar to 91% total reduction were introduced in the hard-to deform Mg alloy by hard-plate rolling process at 400 degrees C for merely 3 and 2 rolling passes. The microstructural morphology and texture were examined, and the tensile tests were performed along rolling direction (RD) and transverse direction (TD). The large-strain rolling process brings in refined grains, homogeneous dispersive LPSO phase and beta phase and weakened basal texture. The anisotropy of the strength and elongation is improved after rolling. The as-rolled sample with similar to 91% total reduction exhibits excellent mechanical properties with ultimate tensile strength (UTS) of 434 MPa, tensile yield strength (TYS) of 318 MPa and elongation to failure (EL) of 10.7% parallel to the TD. By quantitating the relation between grain orientations and the deformation modes, it is confirmed that the basal slip and prismatic slip are the dominant deformation modes at the initial stage of plastic deformation, meanwhile the pyramidal slip and extension twinning are the complementary deformation modes.