Strength-ductility synergy in a wrought AZ80 magnesium alloy by microstructure engineering

Abstract

The present investigation is conducted on microstructure engineering of a Mg–8Al-0.5Zn (AZ80) alloy by different processing routes including conventional aging, cold rolling followed by aging, and aging followed by warm and hot rolling in order to find a strength and ductility synergy. Aging at 175 °C followed by hot rolling at 200 °C is suggested to obtain remarkable mechanical properties with a strength of ∼450 MPa together with an acceptable total elongation of ∼8%. This procedure decorates a bimodal microstructure containing a low-volume fraction of discontinuous precipitates at the grain boundaries and a high-volume fraction of fine continuous precipitates in grain interiors. Microstructural analyses and a microstructure-based strength calculation confirm that the recommended thermomechanical treatment leads to bimodal structure and grain boundaries strengthening together with increasing precipitation strengthening significantly by reducing the size of CP and increasing CP/DP. Achieving superior mechanical properties without adding alloying elements for strengthening is the main advantage of the proposed method. It is suggested that aging followed by hot rolling plays a pivotal role in engineering the microstructure to improve the mechanical properties of AZ80 alloy which is applicable to other age-hardenable magnesium alloys.