Microstructural Stability of a Niobium Single Crystal Deformed by Equal Channel Angular Pressing

A [211]-oriented niobium single crystal was deformed by equal channel angular pressing (ECAP) at room temperature using the route B-c to a total strain of 9.2. A sharp cube texture develops after ECAP processing. The deformed samples were annealed in vacuum from 400 degrees C (673 K) to 900 degrees C (1173 K) for 1 h to evaluate their microstructural stability. Scanning electron microscopy (SEM) was used to image the microstructures of as-deformed and annealed specimens. Electron backscatter diffraction (EBSD) was employed to determine the respective microtextures before and after annealing. Coarsening of the microstructure occurs at a maximum rate at 550 degrees C (823 K) due to discontinuous recrystallization. Normal grain growth replaces discontinuous recrystallization as the main coarsening mechanism above 700 degrees C (973 K)