SUPERPLASTIC DEFORMATION-BEHAVIOR OF A RAPIDLY SOLIDIFIED AL-LI ALLOY

This study aims at investigating the superplastic behavior of a rapidl y solidified Al-3Li-1Cu-0.5Mg-0.5Zr (mass%) alloy. Although rapidly so lidified AI-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 al loy resulted in a much improved superplastic ductility, e.g, elongatio n of approximately 530%. In the case of testing at 520 degrees C, opti mum strain rate of forming was 4 x 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 practi cal application of superplastic deformation of the alloy. It could als o be seen that the microstructure of the deformed alloy was similar to that of the as-received or the TMT treated alloy since continuous rec rystallization was accomplished by subgrain growth and the growth of p rimary grains was prevented by fine beta' (Al3Zr) particles. (C) 1998 Elsevier Science S.A. All rights reserved.