Superplastic-Like Behavior in Coarse Grained Mg-Al Solid Solutions

Abstract

The high temperature ductility of coarse grained Mg-2.7 mol%Al and Mg-4.5 mol%Al alloys has been investigated. Both alloys showed superplastic-like elongation over 250% at 723 K. The superplastic-like deformation is rate controlled by solute drag of dislocations which often governs the creep of what is called Class I solid solution alloys. As for the ductility in solute drag creep, the number of slip systems is essential. The number of slip systems in magnesium alloy is only three at room temperature. However, superplastic-like behavior appears at high temperature, since non-basal slip is activated. Superplastic-like elongation observed in Mg-Al alloys is thus comparable to that observed in both Al-Mg and Al-Cu alloys.