Evolution of stir zone microstructure during FSP of cast NiAI bronze

Abstract

The evolution of the stir zone microstructure during single-pass and multi-pass 'FSP of an as-cast NiAl bronze material was evaluated by optical and high-resolution scanning electron microscopy (SEM) methods, including orientation imaging microscopy (OIM). Deformation commences ahead of the tool as the local temperature exceeds the eutectoid temperature ("800'C) while subsequent recrystallization in the primary a is accompanied by dissolution of Kiv particles dispersed in this constituent. The recrystallized a grains remain equiaxed and appear annealed despite large displacements onward into the resulting stir zone (SZ). Characteristic shear texture components are retained in the thermomechanically affected zone (TMAZ) but the texture of the primary a becomes random after recrystallization and remains so into both single-pass and multipass SZs. Mechanisms to account for recrystallization and subsequent deformation are proposed.