Three-dimensional investigation of particle-stimulated nucleation in a nickel alloy

By combining a focused ion beam (FIB) microscope with a field emission gun scanning electron microscope, it is possible to sequentially mill away ∼50 nm sections of a material by FIB and characterize, at high resolution, the crystallographic features of each new surface by electron backscatter diffraction (EBSD). The successive EBSD maps are subsequently combined to generate three-dimensional crystallographic maps of the microstructure. FIB-EBSD tomography was used to investigate the deformation and recrystallization behaviour of a nickel alloy containing coarse silica particles. The technique demonstrated unambiguously the influence of particle diameter on the misorientations generated within particle deformation zones and showed that particle-stimulated nucleation (PSN) of recrystallization occurred at particles greater than ∼1 μm. PSN also often generated groups of contiguous grains separated by both coherent and incoherent twin boundaries. It was found that much of the behaviour observed using FIB-EBSD tomography is not clearly evident in two-dimensional EBSD micrographs.