Development of high strength and formability Mg-6Zn-0.2Ca alloy via multi-pass warm rolling and aging treatment

Mg-Zn-Ca alloys with high Zn contents tend to form undesirable coarse precipitates, which greatly limits the significant potential of Zn and Ca in texture weakening, leading to poor formability. Hence, to prepare the Mg-6Zn-0.2Ca (wt. %) (ZX60) alloy with improved formability and high strength, we reported a novel processing technique that involves multi-pass warm rolling & annealing, followed by pre-strain and aging treatment. The annealed ZX60 alloy has a fine grain structure (~5 μm) and weakened basal texture, which contributes to a satisfactory Index Erichsen (I.E.) value of ~5.9 mm. After undergoing pre-strain and aging treatment, the sample exhibits excellent strength, i.e. yield strength (YS) of ~267 MPa and ultimate tensile strength (UTS) of ~333 MPa. The formation of weakened basal texture is mainly due to the dissolution of Ca2Mg6Zn3 precipitates, improving the solute dragging effect. Meanwhile, dislocations introduced by pre-strain can act as the diffusion paths for solute atoms, and facilitate the uniformly distributed precipitates during the aging treatment, which results in high tensile strength. This work will be helpful for developing Mg-Zn-Ca alloys with high performance and extending the application of wrought Mg alloys in industries.