Grain boundary misorientation dependence of β phase precipitation in an Al-Mg alloy

Precipitation of beta phase (A13Mg2) in an Al-Mg alloy is investigated by in situ heating and precession diffraction-based orientation imaging in a transmission electron microscope. Initial beta formation occurs more readily at low-angle grain boundaries than at high-angle boundaries; however, larger precipitates are found at high-angle boundaries. We propose a mechanism for beta formation based on boundary energy and grain boundary free volume. These results advance the understanding of beta phase formation, aiding future corrosion prevention. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.