Homogenization of an al-mg alloy and alligatoring failure: influence of the microstructure

Abstract

In this study the influence of the microstructure of Al-5.1Mg-0.7Mn alloy on the propensity towards an alligatoring failure was evaluated. The morphology of the constituent particles appears to be the key factor, with dissolution and fragmentation of fibrous Mg-Si-Sr and transformation of the Al-6(Fe,Mn) into more compact shapes taking place at homogenization temperatures above 520 degrees C, contributing to improved ductility and diminished propensity towards alligatoring. Homogenization at temperatures below 500 degrees C gave rise to a non-uniform precipitation of the dispersoids. Such a microstructure favored localized slip that induced stress concentration at the grain boundaries and triggered grain boundary embrittlement.