Abstract

Niobium ingots obtained by electron beam melting display a typical oligocrystalline microstructure. This kind of microstructure leads to a very heterogeneous microstructure regarding final grain size and texture after deformation and subsequent annealing. Longitudinal sections of 150-mm diameter niobium ingot were cold rolled up to 80% in múltiple passes and then vacuum annealed at 1200°C for 1 hour. After recrystallization annealing the average grain size was determined by two distinct methods: an image analysis routine developed for optical microscopy and by automated EBSD - Electrón Backscattered Diffraction data. The results determined by both techniques were rather similar.