Evolution of microstructure and microtexture upon recrystallization of submicrocrystalline niobium

Laws of recrystallization in niobium after a submicrocrystalline structure was formed in it by high pressure torsion at room temperature are studied by transmission and scanning electron microscopy. Recrystallization is shown to begin at 300 degrees C due to the growth of individual microcrystallites. Continuous recrystallization develops in the temperature range 300-800 degrees C. As isothermal annealing temperature is increased, the area occupied by recrystallized grains, which (110) planes are parallel to the sample surface, increases to 90%. Discontinuous and continuous recrystallization that takes place simultaneously upon annealing at 900 degrees C results in grain refinement and more pronounced size inhomogeneity in the structure. The grain refinement is accompanied by a smearing of the recrystallization texture.