Evolution of microstructures and mechanical properties of Mg-1.4Gd-1.2Y-0.4Zn-0.5Al sheets with different extrusion ratios

In this study, the microstructures and mechanical properties of the as-extruded and as-aged Mg-1.4Gd-1.2Y-0.4Zn-0.5Al (at.%) sheets with two extrusion ratios (ERs) of 10 and 22 have been studied. During the extrusion process, the 18R LPSO structure goes through the process of kink deformation, breaking into pieces, bending-delamination, finally separating and kink again. The as-extruded sheet with ER of 22 exhibits smaller dynamically recrystallized grains and weaker basal texture. Different extrusion ratios play little effect on the aging process. Dense nano-scaled β′ phase precipitates from the α-Mg matrix, resulting in significant precipitation strengthening. The as-aged sheet with ER of 22 exhibits the higher comprehensive mechanical property, where the ultimate tensile strength, yield strength, and tensile elongation to failure are 440 MPa, 328 MPa and 7.0%, respectively. The enhanced strength is mainly attributed to the thin strip-shaped 18R LPSO structure distributed along the grain boundaries, which can effectively refine the grains and strengthen the alloy by acting as reinforcing fibers. •A deformation model of the 18R LPSO structure based on the kink deformation was proposed.•A new 18R LPSO structure containing Al element was found.•The relationship between microstructure and mechanical properties was investigated in detail.