Recrystallization behavior of a cold-rolled niobium bicrystal

A high-purity coarse-grained niobium bicrystal was 70% cold rolled in multiple passes. Deformation occurred in an inhomogeneous manner in both grains giving rise to a banded structure. In consequence, highly misoriented boundaries were developed in the microstructure in a wide range of misorientations, many reaching about 55°. These boundaries act as effective nucleation sites for recrystallization. The microstructure of both grains was investigated using electron backscatter diffraction (EBSD) in the cold-worked state in order to quantify the misorientations (ψ) associated to these bands. Upon annealing at 800 and 900 °C, the new recrystallized grains were nucleated preferentially at deformation heterogeneities and in the vicinity of the prior grain boundary in this bicrystal.