Precipitation and corrosion behaviour of nano-structured near-surface layers on an AA6111 aluminium alloy

Abstract

A nano-structured, near-surface layer has been generated by mechanically grinding an AA6111 alloy. After heat treatment at 180°C for 30 minutes, Q phase particles, ∼20 nm diameter, were precipitated preferentially at grain boundaries within the nano-structured nearsurface layer. No such precipitates were observed in the bulk alloy after this heat treatment. This preferential precipitation results in the near-surface layers having increased corrosion susceptibility than the bulk microstructure, due to the micro-galvanic coupling between the precipitates at grain boundary and the grain matrix. The localized attack is predominately intergranular. © 2006 IOP Publishing Ltd.