The effect of Mn containing dispersoids on the distribution of slip and fracture mode in Al-Mg-Si-Mn alloys

Abstract

Improvements in the fracture performance of Al-Mg-Si extrusions are required to meet the demands of the automotive market. The fracture mode and the associated ductility results from competition between transgranular and intergranular fracture paths where intersection of slip bands and grain boundaries plays a significant role. In this study, the distribution of plastic strain within grains for microstructures with different spacings of Mn dispersoids was quantified using high resolution digital image correlation. It was observed that plastic strain was organized into slip bands where the magnitude of local shear strain decreased with reduced inter particle spacing of the dispersoids. It is proposed that this leads to a lower stress concentration on the grain boundary, decreasing the propensity for intergranular fracture. This was consistent with the findings that intergranular fracture was dominant in the dispersoid free material whereas low and high densities of dispersoids gave rise to a transgranular fracture mode.