Effect of Rolling Schedule on Microstructure and Properties of Mg-Ca-Mn-Sn Sheet

Achieving an excellent combination of high strength and ductility in low-alloy magnesium (Mg) alloys is a great challenge. In this work, a new Mg-1.03Ca-0.47Mn-2.39Sn alloy was designed. The extruded sheet has a low ultimate tensile strength (UTS, ~268 MPa) and total elongation (EL, ~7.5%). However, after rolling and annealing, the strength and plasticity are greatly improved. It is noted that the UTS and EL increased simultaneously with the increase in a rolling pass and cumulative reduction. Especially, an excellent combination of UTS of 310 MPa and EL of 22% is achieved by 4-passes hot rolling and the fifth pass differential speed rolling. Microstructural results show that the high strength is mainly attributed to the uniformly fine grain size ( ~4.5 μm) and the high-density striated CaMgSn and globular Mg₂Ca precipitates. In addition, the uniform grain size, weaken transverse direction-split texture and the activation of multiple slips systems all contribute to the enhanced ductility. These findings provide an effective method for manufacturing low-alloy Mg alloys with high strength and ductility by rolling.