Evolution of potassium bubbles and its influences on the recrystallization behaviour of swaged tungsten rods with high potassium doping level

Recrystallization temperature (RCT) is a key factor influencing the working temperature window of tungsten (W)-based plasma facing materials (PFMs). To investigate the effects of potassium (K)-bubbles on the recrystallization behaviour of the W rods with a high K-doping level of 96 ppm, large size sintered K-doped W ingot with a diameter of 70 mm (total weight of 42 kg) was fabricated via powder metallurgy route. The ingot was reduced to various diameters with logarithmic strains up to 3.53 by a series of high-speed forging and swaging. Then the rods were treated by 1-h isochronal annealing at temperatures ranging from 1350 °C to 2050 °C in the H2 atmosphere. Results showed that as the logarithmic strain increased, the RCT increased and reached a maximum value of 1820 °C at the logarithmic strain of 2.95. Then, it decreased at a higher logarithmic strain of 3.53. The K-tubes in the rods with heavy deformation have experienced a ‘dynamic break-up’ during swaging. This influenced the evolution and morphology of K-bubbles in the subsequent annealing. The RCT of high K-doped W with heavy deformation was determined by the synergetic effects of the internal stored energy and the morphology of K-bubbles.