Strain Rate Sensitivity and High Temperature Deformation Mechanisms of Cast Zn-22Al Alloy Foams

Zn-22Al eutectic alloy is a typical superplastic material which exhibits over 500% elongation at high temperature. Superplastic Zn-22Al alloy foams were successfully manufactured through a conventional casting process. Foaming temperature was about 750 K which was lower than that of conventional aluminum foams. The porosity of Zn-22Al alloy foams is between 50 and 80%. The cell wall consisted of fine equiaxial crystal grains after solution treatment. High temperature deformation behavior of Zn- 22Al alloy foams was evaluated through tensile and compressive tests at high temperature. Zn-22Al alloy foams exhibited high strain rate sensitivity of 0.55, which was caused by superplastic deformation of the cell wall material. High temperature deformation mechanism can be explained using the new parameter of local strain rate. The Zn-22Al foams showed relatively high ductility at high temperature compered to aluminum foams. This is because of the superplastic deformation induced by the fine microstructure in the cell wall. In addition, most superplastic materials have excellent damping property due to their grain boundary sliding. Present Zn-22Al foams are applicable as either shock absorbing or damping material in the future.