Effects of Ca addition on the microstructures and mechanical properties of as-extruded Mg–Bi alloys

The microstructure and mechanical properties of as-extruded Mg–1.3Bi–xCa (x = 0, 0.4, 0.9, and 1.3 wt%) were investigated. All samples exhibit full dynamic recrystallization; the mean grain size first increases slightly and then decreases significantly. Additionally, both Mg₂Bi₂Ca and Mg₂Ca phases are formed with increasing Ca content. In particular, the dynamic precipitation of nanoscale Mg₂Ca is enhanced remarkably. The typical fiber basal texture in Ca-free binary alloy transformed into a rare-earth texture with the components of [1¯21¯l] and [011¯l]//extrusion direction in Ca-bearing ternary alloys. In addition, the tensile elongation increases significantly with a trace amount of Ca addition (0.4 wt%), but an overdose of Ca addition (1.3 wt%) results in the formation of a large number of microscale Mg₂Bi₂Ca phases. The Mg-1.3Bi-0.9Ca alloy demonstrates the optimal balance of ductility and strength with an excellent elongation of 40% and yield strength of 158 MPa, owing to texture modification and grain refinement. This study may provide insights into the development of high-ductility, low-cost Mg–Bi-based alloys using microstructure tuning and texture modification.