Large-scale potassium-doped tungsten alloy with superior recrystallization resistance, ductility and strength induced by potassium bubbles

Potassium-doped tungsten (KW) plate with a weight of 25 kg was prepared by hot rolling. Subsequently, part of the KW suffered annealing at 1600, 1800 °C for 0.5 h. For the rolled state, K bubble showed the size and number density of 71 nm, 7.6×1018 m−3 in the grain interior and 98 nm, 1.9×1019m−3 at the grain boundaries. To figure out the influence of K bubbles on recrystallization resistance and mechanical properties, microstructure and tensile performance were examined on the stress relieved and high-temperature annealed KW. The results indicated that the KW displayed excellent recrystallization resistance as the K bubble strings inhibited the transverse movement of grain boundaries. Tensile tests at 100, 150, 200, 250, 300, 500 and 700 °C showed the DBTT was 50–100 °C for the stress relived KW and about 200 °C for the high-temperature annealed KW. Moreover, the KW plate exhibited large ductility as K bubbles in the grain interior can act as the source to emit dislocation and barrier to dislocation movement thereby lead to lots of mobile dislocation. Besides, the high number density of nano-sized K bubbles also improved the KW strength, and the strength contribution of K bubbles calculated by the Orowan mechanism was 245.6 MP at room temperature.