Hardness loss and microstructure evolution of 90% hot-rolled pure tungsten at 1200-1350 °C

Tungsten is a promising plasma-facing material because of its low sputtering yield, high melting point and high thermal conductivity. The hardness loss and microstructure evolution of pure tungsten hot-rolled to 90% thickness reduction is investigated by isothermal annealing at temperature range of 1200-1350 °C. Changes in the mechanical properties caused by recovery and recrystallization during heat treatment are detected by Vickers hardness measurements. Additionally, the microstructural evolution is analyzed with light optical microscopy and X-ray diffraction. The results indicate that the hardness evolution can be divided into two stages: recovery and recrystallization. Recrystallization of W90 in the temperature range of 1200 to1350 °C is governed by the same activation energy as grain boundary diffusion. The average recrystallized grain size is larger for lower annealing temperatures.