Effect of thermomechanical processing and solution strengthening on the superplasticity of an Al-Mg-Cr alloy

摘要

The effect of transition element andthermomechanical processing(TMP) on the superplastic behaviorof Al-7%Mg-0.3Cr alloys were examined and correlated to themicrostructural evolution during superplastic deformation. Toestablish an optimum manufacturing process for the enhancedsuperplastic properties, different processing methods such as warmrolling and cold rolling were used. In cold rolled Al-7%Mg-0.3%Cr alloys with intermediate annealing, the maximumelongation (close to 730%) was observed at 530℃. On the otherhand, low temperature superplasticity was not observed in Al-7%mg-0.3%Cr alloys with the TMP developed by Mcnelleybecause of the suppression of continuous recrystallization due tothe dispersion of intermetallics. However, when these TMPed Alalloys were tested at high enough temperatures above therecrystallization temperature, the maximum elongation reachedapproximately 400%. In this study, the possible effect of solute-dislocation interaction on the high temperature ductility was alsoexamined. The predicted strain rate range of high ductilityassociated with high strain rate sensitivity due to solutestrengthening coincides with the range of high temperaturesuperplasticity of Al-Mg alloys, suggesting solute strengtheningmay be contributory to high temperature superplasticity of Al-Mg alloy.