An Analysis of Strength and Ductility of Ultrafine Grained Al Alloys

Abstract

This paper brings together and compares data of various ultrafine grained (UFG) Al alloys processed through different routes. In general, the trend of decreasing ductility with increasing strength was observed for the UFG alloys. As compared to the coarse grained (CG) alloys, the UFG alloys show a lower ductility, a lower extent of work-hardening and a lower uniform elongation. Unlike the CG alloys, which show a large fraction of uniform to total elongation, in UFG alloys this fraction varies with processing technique. It is shown here that aging of some UFG Al alloys improves ductility. Further, it is shown that increasing the equivalent strain of pre-deformation increases ductility. From this it was inferred that high angle grain boundaries have an important influence on ductility. The variation of ductility with strain rate sensitivity has been found to match both the analytical prediction as well as data of various materials.