A high-performance Mg-Al-Sn-Zn-Bi alloy fabricated by combining sub-rapid solidification and hot rolling

Abstract

The development of wrought Mg alloys with high alloying contents is greatly restricted by the negative influence of coarse aggregative second phases originating from the casting process. In the present work, we reported a high-performance Mg-5Al-2Sn-2Zn-0.5Bi (wt%, ATZB5220) alloy fabricated by combining sub-rapid solidification (SRS) and controlled hot rolling. The microstructure of the as-cast alloy was greatly refined by the SRS with a high cooling rate (~350 °C/s). The micro-segregation of different alloying elements was also alleviated by the SRS to varying degrees. The improvement degrees of micro-segregation for Al and Sn solutes were much higher compared with Zn and Bi. The SRS sample obtained more uniform and finer (~3 μm) grains than the conventional solidified counterpart after hot rolling (a reduction of ~70%) and annealing treatment, which mainly benefited from the finer as-cast microstructure under the SRS. Eventually, the high-alloyed ATZB5220 sample following the SRS route showed a good combination of strength and ductility, exhibiting an ultimate tensile strength (UTS) of ~356 MPa, yield strength (YS) of ~267 MPa, and elongation to failure (δf) of ~13%. This work provides a novel strategy to fabricate high-performance Mg alloy sheets with high alloying contents.