Spheroiding and refining of coarse CaMgSn phase in Mg-Al-Sn-Ca alloys for simultaneously improved strength and ductility via sub-rapid solidification and controlled rolling

Here we report a novel Mg-4.5Al-1.5Sn-0.5Ca (wt%) alloy with high mechanical properties produced via sub rapid solidification (SRS) and controlled rolling. In virtue of SRS combined with homogenization treatment, the morphology of CaMgSn phase changes from long-rod to refined spherical/quasi-spherical, which cannot be achieved via conventional solidification (CS) followed by homogenization treatment. By subsequent controlled rolling, dispersed nano-sized CaMgSn precipitates (similar to 16 nm) could form in Mg-4.5Al-1.5Sn-xCa alloys (x = 0.3 and 0.5 wt%). Compared to the rolled Mg-4.5Al-1.5Sn alloy, the rolled Mg-4.5Al-1.5Sn-0.5Ca alloy shows an impressive combination of strength (a yield strength of similar to 275 MPa and an ultimate tensile strength of similar to 338 MPa) and ductility (an elongation of similar to 20%). The increase in yield strength is mainly due to grain boundary strengthening, Orowan strengthening and texture strengthening. The high ductility is enhanced prominently as a result of dispersed nano-sized CaMgSn precipitates. The present work proposes a novel processing strategy to spheroid and refine coarse eutectic CaMgSn phase with a high melting point, which is important in achieving a good synergy of strength and ductility for Mg alloys.

Automated summary

A novel Mg-4.5Al-1.5Sn-0.5Ca alloy with high mechanical properties was produced via sub rapid solidification and controlled rolling. The morphology of CaMgSn phase changed from long-rod to refined spherical/quasi-spherical through the processing strategy proposed in this study. The alloy exhibited impressive strength (yield strength of approximately 275 MPa and ultimate tensile strength of approximately 338 MPa) and ductility (elongation of approximately 20%) due to the formation of dispersed nano-sized CaMgSn precipitates.