Superplastic deformation behavior of fine grained 1420 Al-Li alloy

The superplastic deformation behavior,the relation between deformation properties and parameters of fine grained 1420 Al-Li alloy were investigated at a temperature range of 440℃~500℃ and at an initial strain rate range of 1×10-4s-1~1× 10-2s-1.The results indicated that the true stress-true strain curves of superplastic deformation showed steady-state type while the initial strain rate was under 3×10-4s-1,but it was softing type while the initial strain rate was over 3×10-4s-1.The peak stress reduced with the temperature increasing and strain rate decreasing.The optimum superplastic deformation was obtained at the temperature of 480℃and the initial strain rate of 1×10-4s-1,while the maximum elongation reached 550%.The elongation increased with initial strain rate decreasing,but it increased firstly and then decreased with temperature rising.Through multiple-sample method and linear-fitting,the strain rate sensitivity index m was 0.41~0.48,and the activation energy Q was 43.5kJ/mol~79.7kJ/mol.