Five-parameter grain boundary characterisation of randomly textured AZ31 Mg alloy

The five-parameter analysis approach was used to measure the grain boundary character distribution of randomly textured AZ31 Mg alloy produced through casting followed by annealing at 450°C for 16 h. The misorientation angle distribution was close to the one expected from the material with a random texture. The grain boundary plane distribution, ignoring the misorientation angle, revealed a relatively weak plane orientation anisotropy, with a preference for grain boundaries terminated on prismatic {hki0} planes. Surprisingly, the population of grain boundary planes was not inversely related to the expected grain boundary energies. Basal oriented grain boundaries are expected to have the lowest energy, but they also had the lowest population. This could result from the presence of residual columnar grains, formed during solidification and remaining after annealing, which increases the relative area of boundary planes with prismatic orientations.