Superplastic aluminium-based alloys

Abstract

Although the phenomenon of super plasticity in metals was recognized for many years, the majority of alloys that were shown to be super plastic consisted of two phases present in approximately equal volumes. The only aluminium alloys known to be superplastic were of eutectic composition and did not, in general, possess other properties that would make them commercially attractive. More recently, superplasticity has been obtained in relatively dilute aluminium alloys with more useful user properties. A brief summary is given of the aluminium alloys of eutectic composition that have been shown to exhibit superplasticity, but the authors are mainly concerned with the newer, relatively dilute alloys. The roles of alloying additions in modifying the recrystallization behaviour, because of both their presence in precipitate particles and their influence in solid solution, are considered. Additionally, possible deformation mechanisms in the newer alloys are discussed to demonstrate the relative importance of various microstructural features in conferring superplasticity.