Effect of External Stress on the POST-Aging MECHANICAL Properties of Rolled Magnesium Alloys

In the current study the effects of conventional aging and stress aging on the microstructure and mechanical behavior of warm rolled AZ31 magnesium alloy were investigated. Tensile experiments revealed that the ultimate tensile strength (UTS) of the as-received AZ31 increased up to 300 MPa after 24 h aging at 120 °C, with a 2% reduction in ductility. Moreover, yield strength of the rolled and stress aged sample at 120 °C under an external stress of 50 MPa and only for 1 h was improved to 240 MPa. Microstructural observations demonstrate that the grain growth firstly reduced the strength of rolled condition while improving the strain at failure. This was followed by the nucleation of recrystallized grains, enhancing the UTS with acceptable ductility. In addition, fracture surface analysis of stress aged samples demonstrated nucleation-controlled fracture mechanisms with deeper void structures as a ductile characteristic.