Superplastic deformation of a rapidly solidified Al-Li alloy

The superplastic deformation characteristics of a rapidly solidified Al-3Li-1Cu-0.5Mg-0.5Zr alloy have been studied in this study. This rapidly solidified Al-Li alloy exhibited a high superplastic ductility e.g., elongation of approximately 800%, when deformed at temperatures above 500degreesC and at the strain rates of 10(-2)/s to 10(-1)/s. Stress-strain rate curves were obtained by performing a series of load relaxation tests in the temperature range from 460degreesC to 520degreesC in order to examine the superplastic mechanism. The stress-strain rate curves could be separated into two parts according to their respective physical mechanisms, i.e., grain matrix deformation and grain boundary sliding as was proposed in a new superplasticity theory based on internal deformation variables. The microstructural evolution during superplastic deformation was also observed by using transmission electron microscopy. During superplastic deformation, grains got into fine equiaxed shape due to the continuous recrystallization.