Super-High Strength Mg–7.5Al–0.8Zn Alloy Prepared by Rapidly Solidified Powder Metallurgy and Low Temperature Extrusion

In this work, Mg–7.5Al–0.8Zn alloy with super-high tensile strength are fabricated by rapidly solidified powder metallurgy (RS/PM) and low temperature extrusion technology. By reducing extrusion temperature from 340 to 170^° C, the α-Mg grains are significantly refined and numerous nanoscale β-Mg₁₇ Al₁₂ particles are obtained. The RS/PM alloy extruded at 170^° C possesses the lowest grain size of ≈550 nm. The nanoscale β-phase particles stimulate the nucleation of dynamically recrystallized (DRXed) grains and restrain the growth of DRXed grains. The RS/PM alloy extruded at 170^° C exhibits mechanical properties with a tensile yield strength of 448 MPa, an ultimate tensile strength of 480 Mpa, and a microhardness of 137 HV. These excellent mechanical properties result from low temperature extrusion are mainly attributed to the ultra-fine DRXed grains and the high-density dislocations and subgrains.