High performance Mg-8Gd-4Y-1Zn-0.5Al alloy with long-period stacking ordered structure by hot rolling

Abstract

The Mg-8Gd-4Y-1Zn-0.5Al (wt%) alloy prepared by metal type casting were homogenized, rolled or extruded-rolled to obtain sheets, and followed by aging treatment. The microstructures were analyzed by OM, SEM, TEM, EBSD and XRD, the hardness and tensile mechanical properties were tested. The results show that the optimal process is rolling at 793 K with the deformation of 70% for the homogenized sheet. The microstructure of the sheet is composed of fully dynamic recrystallized grains with a strong basal texture, and the aggregated 18R-LPSO structures randomly distribute in the matrix. After peak aging treatment, the yield strength (YS), ultimate tensile strength (UTS) and elongation to failure (EL) of the sheet are 343 MPa, 380 MPa and 7.5%, respectively. After the extruded sheets were rolled at 793 K with 50% deformation, the grains grew up. The texture changes from a silk type to the strong basal type. The 18R-LPSO structures reduce the torsion phenomena, but get together. After peak aging treatment, the YS, UTS and EL reach 391 MPa, 462 MPa and 5.5%, respectively. The 18R-LPSO structures with streamlined distribution along rolling direction increase the anisotropy of mechanical properties of the extruded-rolled sheet.