On the effects of second phase distribution on the fracture behaviour of two superplastic aluminium alloys

Abstract

The significant scatter observed in the elongation to fracture of specimens taken from a single, industrially processed sheet for two Al alloys has been traced to changes in the value of the strain rate sensitivity index (m) and also to the specimen to specimen variation in the concentration and distribution of second phase particles/inclusions. It is shown that these three variables of m, second phase particle content and distribution affect the width of tear ridges, the size of clusters of grains that pull out as a whole during fracture, their connectivity and the extent to which cavitation can be suffered before final fracture. The consequences of these effects for specimen ductility are discussed.