Recovery and recrystallization kinetics of differently rolled, thin tungsten plates in the temperature range from 1325 °C to 1400 °C

The thermal stability of thin tungsten plates of four different thicknesses achieved by warm- and (in two cases) cold-rolling is investigated in the temperature range between 1325 degrees C to 1400 degrees C. Hardness testing of annealed specimens allows tracking the degradation of the mechanical properties and, indirectly, the involved restoration processes during the microstructural evolution. For all four tungsten plates, a concise description of both, isothermal and isochronal annealing treatments is achieved using well-established models for the kinetics of recovery and recrystallization. A systematic dependence of the recovery kinetics at different temperatures on the hardness loss during recovery at a particular temperature has been identified. For the recrystallization kinetics, an Avrami exponent of 2 is observed in general. On the other hand, the activation energies revealed for different characteristic times of the recrystallization process depend on the plate thickness (or more precisely, the defect density stored). These findings, in particular, an activation energy far below that of short circuit diffusion, indicate the possibility of persisting nucleation throughout annealing.