Lightweight magnesium (Mg) alloy sheets have attracted considerable attention for potential applications in transportation vehicles. However, their poor formability at room temperature (RT) hinders the wider applications. This work presents an advantage of precipitation-hardenable wrought Mg alloys in simultaneously achieving excellent RT formability and high strength.
Micro-addition of Zn and/or Al into Mg-0.5Ca (wt.%) alloy causes a substantial increase in the peak-hardness due to the precipitation of Guinier Preston (G.P.) zones. The hot-rolled Mg-1.1Al-0.3Ca-0.2Mn-1.6Zn alloy shows poor room temperature formability due to the development of a strong basal texture. However, because the solution treatment facilitates the nucleation of weakly textured grains at twin boundaries, the solution treated sample exhibits comparable RT formability with 6XXX series Al alloys. Subsequent paint baking process at 170 ֯C for 20 min results in a substantial increment of the yield strength from 160 to 240 MPa, realizing the best formability-strength balance in Mg sheet alloys. This is attributed to the formation of a high number density of solute-clusters and dislocation locking owing to the solute segregation to the dislocations. In the presentation, the possibility to achieve the high strength by precipitation hardening in fine-grained Mg alloys will be also discussed.
