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 rolling direction (RD) and transverse direction (TD) at –50, 25, 50, 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. Electron backscattered diffraction (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.