Formation of a new incoherent twin boundary in a Mg–3Gd alloy

Abstract

Ordered-segregated Gd atoms in coherent twin boundaries (CTBs) improve the strength of Mg–Gd alloys after annealing. Here we show a new kind of incoherent twin boundary (ITB) with Gd segregation after annealing in a Mg–3Gd alloy. This new ITB (ITB') does not lie on 101¯2 twinning plane, nor is it parallel to [12¯10]. The thick morphology of this ITB' is due to twinning plane rotation around [0001]Twin by uncertain angles (~7° and ~13° observed). The ITB', driven by dislocation rearrangement in the boundary and total system energy reduction, is supposed to have higher strengthening effect than normal ITB and CTB.