In this work, a good balance of strength and ductility (a yield strength of ~185 MPa and a uniform elongation of ~20%) has been obtained in a dilute Mg-1.8Zn-0.3Y-0.3Ca-0.3Zr (wt.%) alloy using hard plate rolling (HPR) followed by annealing, with a low anisotropy in mechanical properties. More importantly, the HPR-annealed alloy shows an excellent formability at the same time, i.e., the index Erichsen (I.E.) value reaches ~7.9 mm (the Erichsen cupping test) at room temperature, which is higher compared with the Mg-1.8Zn-0.3Y-0.3Ca-0.3Zr alloy produced by conventional multi-pass rolling (CR) followed by annealing. The excellent synergy of strength and formability of the HPR-annealed alloy is mainly attributed to a weak elliptical ring texture, as well as finer and denser Zn₂Zr₃ precipitates. The formation of weak elliptical ring texture is related to the preferential co-segregation of Zn and Ca elements at boundaries of basal grains with small misorientation angles during annealing, which inhibits the growth of basal grains and promotes the preferential growth of non-basal grains. At the same time, in comparison with the CR-annealed alloy, the HPR-annealed alloy contains finer and denser Zn₂Zr₃ precipitates that are less likely to become sources of cracks, leading to the higher strength and formability of the HPR-annealed alloy. The results in this work can provide reference for the development of high strength Mg alloy sheets with excellent room temperature formability, which also shed light on mitigating planar anisotropy in mechanical properties for Mg alloy sheets.

The preparation of large-scale magnesium (Mg) alloy parts by wire arc additive manufacturing (WAAM) has broad application prospects, including automotive and aerospace industries. The chemical composition of Mg alloy wires plays a critical role in determining mechanical properties of WAAM Mg alloys. However, types of Mg alloy wires for WAAM need to be extended, in order to improve mechanical properties. Therefore, in the present work, a novel ATZM31 Mg alloy wire has been prepared and applied to the cold metal transfer (CMT)-WAAM process. This study focuses on understanding the forming quality, microstructure evolution, and mechanical properties of the ATZM31 alloy thin-wall component fabricated by WAAM. The results show that the Mg alloy thin-wall component possesses satisfactory formability, with minor sidewall roughness. The ATZM31 thin-wall component is mainly composed of columnar dendrites and equiaxed dendrites of the α-Mg phase, with the η-Al₈Mn₅ phase distributes dispersedly at grain boundaries. The area fraction of the η-Al₈Mn₅ phase is estimated to be ~0.21% based on the statistical analysis of SEM images. Due to different cooling behaviors, the distribution of grain size along the build direction of the thin-walled component is uneven. The average grain size is ~46 µm, ~74 µm and ~61 µm at the bottom, middle and top of the ATZM31 alloy thin-wall component, respectively. From the substrate to the top of the ATZM31 alloy thin-wall component, the hardness decreases gradually. The ultimate tensile strength along the deposition direction and build direction are ~225 MPa and ~214 MPa, respectively, without pronounced anisotropy. The ATZM31 alloy thin-wall component fabricated by WAAM exhibits a comparable ultimate tensile strength to forged AZ31 Mg alloys and weaker anisotropy than wrought Mg alloys.

Developing low-cost rolled Mg alloys with both high strength and ductility is desirable, while the improved strength is generally accompanied with decreased ductility. Here, by using rotated hard-plate rolling (RHPR) with a total thickness reduction of ~85%, we obtained a Mg−8Al−0.5Zn−0.8Ce (wt.%, AZ80−0.8Ce) alloy with a high strength-ductility synergy, i.e., the yield strength (YS), ultimate tensile strength (UTS) and elongation-to-failure (EF) are ~308 MPa, ~360 MPa and ~13.8%, respectively. It reveals that the high YS is mainly originated from grain boundary strengthening (~212 MPa), followed by dislocation strengthening (~43 MPa) and precipitation hardening (~25 MPa). It is found that a relatively homogeneous fine grain structure containing a large fraction (~62%) of low angle boundaries (LABs) is achieved in the RHPRed alloy, which is benefit for the high tensile EF value. It demonstrates that LABs have important contributions to strengthening and homogenizing tensile deformation process, leading to the simultaneous high strength and high EF. Our work provides a new insight for fabrication of low-cost high performance Mg alloys with an excellent strength-ductility synergy.