Intergranular ductile fracture of Al-Mg₂Si base alloys with excess Si

Intergranular fracture of an Al-1%Mg₂Si-0.4%Si-0.2%Mn alloy with various grain sizes was investigated by tensile test, optical microscopy, and scanning and transmission electron microscopy. In peak aged condition, both spacing of precipitates in the matrix and width of PFZ, as well as dimple size of intergranularly fractured surface, are almost independent of the grain size. Under the investigated aging conditions, both mean height and width of slip bands at 1% strain increase with grain size. The influence of mean slip bands width on fracture stress is, however, scarcely distinguished in this alloy.