Fracture mechanism of Zr₂Si precipitate equilibrated in a solution-treated Si-modified Zircaloy-4

Secondary phase precipitates are vital to control corrosion, mechanical and irradiation response of multi-phase metallic alloys. As a model system, this work analysed hcp-Zr to fcc-Zr transformation-induced failure in a C16 type body-centred tetragonal Zr2Si binary precipitate using transmission electron microscopy and related techniques. The configurations of two types of dislocations, < 001 > {110} and < 110 > {001}, were approximated which interlocked along the major axis of Zr2Si precipitate constituting the sessile junctions. Threading dislocations resisted further glide, and failure occurred along the minor axis. Peierls stress and dislocation energy were estimated for the most favourable <001> {110} slip system and, in turn, probability of dislocation climb in Zr2Si precipitate was evaluated as a high temperature phenomenon, also evidenced by a prismatic dislocation loop along (110) plane.