Superplastic deformation behavior of a rapidly solidified Al–Li alloy

This study aims at investigating the superplastic behavior of a rapidly solidified Al–3Li–1Cu–0.5Mg–0.5Zr (mass%) alloy. Although rapidly solidified Al–Li alloys have the very fine grain structure desirable for improved superplasticity, unfavorable oxide morphology often prevents them from being superplastic. The results of superplastic deformation indicated that the proper thermo-mechanical treatment (TMT) of the alloy resulted in a much improved superplastic ductility, e.g. elongation of approximately 530%. In the case of testing at 520°C, optimum strain rate of forming was 4×10−2 s−1, which was one or two orders of magnitude higher than that of ingot cast Al–Li alloys. Such a high strain rate was thought to be quite advantageous for the practical application of superplastic deformation of the alloy. It could also be seen that the microstructure of the deformed alloy was similar to that of the as-received or the TMT treated alloy since continuous recrystallization was accomplished by subgrain growth and the growth of primary grains was prevented by fine β′ (Al3Zr) particles.