Experimental study of the mechanical properties at elevated temperatures in commercial Mg-Al-Zn alloys for superplastic forming

The mechanical properties in two commercial Mg-Al-Zn alloys were investigated at elevated temperatures. The alloys were examined for tensile tests and then characterized. The deformation mechanism in two alloys varied with their grain sizes. A coarse-grained(>100 mu m) alloy exhibited a strain rate sensitivity of similar to 0.33, and fractured with significant development of necking. On the other hand, finer-grained alloys with grain sizes less than 20 mu m exhibited a high strain rate sensitivity similar to 0.5, and failed with brittle fracture corresponding to the cavity growth. The grain size dependence on the tensile properties was discussed to apply these alloys for superplastic forming.