Influence of Ca plus Bi on tensile and strain hardening behaviour of AZ91 alloy

The influence of Ca + Bi on the tensile and strain hardening behaviour of the AZ91 alloy at ambient and elevated temperatures have been examined. The values of YS are higher, and ductility is lower of all the modified alloys. The UTS of the modified AZ91 alloys is lower except at 473 K. The UTS values decrease with an increase in test temperature for all the alloys. The improved YS of the modified alloys is owing to reduced grain size. The brittle Mg3Bi2, Al2Ca and Bi3Ca5 phases in the modified alloys reduce their UTS and ductility. The transgranular cleavage fracture at 298 K changes to quasi-cleavage fracture at 473 K. Several dislocations piled up around the beta-Mg17Al12 and Al2Ca phases are seen.