Tensile Failure Mode Transitions from Subzero to Elevated Deformation Temperature in Mg-6Al-1Zn Alloy

Understanding the temperature dependent deformation behavior of Mg alloys is crucial for their expanding use in the aerospace sector. This study investigates the deformation mechanisms of hot-rolled AZ61 Mg alloy under uniaxial tension along RD and TD at -50 °C, 25 °C, 50 °C, and 150 °C. Results reveal a transition from high strength with limited elongation at -50 °C to significant softening and maximum ductility at 150 °C. TD samples consistently showed 2-6% higher strength than RD; however, this yield anisotropy diminished at 150 °C due to the shift from twinning to thermally activated slip and recovery. Fractography indicated a change from semi-brittle to fully ductile fracture with increasing temperature. EBSD analysis confirmed twinning-driven grain refinement at low temperatures, while deformation at high temperatures involved grain elongation along shear zones, enabling greater strain accommodation before material failure.