INTERFACIAL CONTROL OF β-PHASE PRECIPITATION IN Al-Mg ALLOYS

摘要

The corrosion behaviour of AA5182 after heat treatment at 70 - 150℃ has been charactersised by AFM and OIM, which revealed little dependence of the degree of corrosion attack on grain boundary misorientation for values above 20°, behaviour that correlated with the degree of grain boundary precipitation. The grain boundary precipitates were found to be the Al_3Mg_2 β-phase, formed diffusionally with interface planes on {111}_α and {112}_α, the former being the primary interface and the latter being an accommodation plane so that the difference between grain boundaries being precipitate-free, discontinuously covered and completely covered depends on the divergence between {111}_α and the grain boundary plane.