Design of multicomponent Mg–Al–Zn–Sn–Bi alloys with refined microstructure and enhanced tensile properties

Owing to the low alloying content in commercial wrought Mg alloys, their strengthening potential is greatly suppressed. It is difficult to achieve the synergy of high strength and formability for Mg alloys. In the present work, a novel high-alloyed Mg–6Al–1Zn–1Sn-0.5Bi (AZTB6110) alloy was designed by multi-component composition design and subjected to a fabrication route coupling sub-rapid solidification and controlled rolling. The alloy has excellent tensile properties, i.e. yield strength (YS) of ~260 MPa, ultimate tensile strength (UTS) of ~363 MPa and elongation of ~15%. The role of Al content (4, 6 and 8 wt %) on microstructure and tensile properties was systematically investigated in the AZTB alloys. When the Al content reaches 6 wt %, the combined pining effects of nano- and submicro-precipitates (Mg17Al12 and Mg2Sn) hinder the grain growth and result in the finest grain size (~3 μm) among the studied alloys. The refined grains as well as densely dispersed fine Mg17Al12 and Mg2Sn particles result in the best tensile yield strength in AZTB6110 compared to the other alloys. Meanwhile, the high ductility is benefited from the strong work-hardening capacity resulting from the interaction of dislocations with Al, Zn, Sn and Bi solutes and numerous nano-precipitates. Such a designed alloy helps to improve the development of high-alloyed multicomponent Mg alloys with high performance, which broadens the composition range and application of traditional wrought Mg alloy sheets.