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 deg. . 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 deg. C, the new recrystallized grains were nucleated preferentially at deformation heterogeneities and in the vicinity of the prior grain boundary in this bicrystal