Tailoring strength-ductility balance of caliber-rolled AZ31 Mg alloy through subsequent annealing

Recently, multi-pass caliber rolling has been shown to be effective for Mg alloys. This study investigated the effect of subsequent annealing on the mechanical properties of a caliber-rolled AZ31 Mg alloy to modulate the strength-ductility relationship. This annealing gave rise to different trends in mechanical properties depending on the temperature regime. Low-temperature annealing (T ≤ 473 K) exhibited a typical trade-off relationship, where an increase in annealing temperature resulted in increased ductility but decreased strength and hardness. Such a heat treatment did not degrade the high strength-ductility balance of the caliber-rolled alloy, suggesting that the mechanical properties could be tailored for different potential applications. In contrast, high-temperature annealing (T > 473 K) caused a simultaneous deterioration in strength, hardness, and ductility with increasing annealing temperature. These differences are discussed in terms of the varying microstructural features under the different investigated annealing regimes. Keywords: AZ31 Mg alloy, Caliber rolling, Annealing, Grain growth, Mechanical improvement, Twinning