Microstructural Evolutions in Helium Irradiated Dispersoid Strengthened Tungsten Alloys

Tungsten is a candidate material for the divertor region of fusion tokamak reactors due to its high melting point, low coefficient of linear thermal expansion, high sputter threshold, and low tritium retention. Transition metal carbide additions by spark-plasma sintering (SPS) has been shown to increase the recrystallization temperature of W with no increase to deuterium retention. High energy helium particles implant themselves in near–surface(nm) regions of tungsten, stabilizing vacancies and coalescing to nanometer–sized bubbles. The growth of He bubbles from incident plasma at elevated temperatures has been observed in W-TiC, W-TaC, and W-ZrC samples, but the effects of the microstructure on the migration of helium warrants further study. Kesternich et al showed the preferential trapping of He for TiC precipitates can be altered by recrystallization at elevated temperatures resulting in a dislocation-sparse microstructure.Samples of W-TaC, W-TiC, and W-ZrC are fabricated via SPS and held at 1600°C in an inert atmosphere to alleviate internal stresses within the microstructure and grow grains. Samples are then irradiated with He to a 3 x 1016/cm2 fluence at 800°C and characterized via scanning electron microscopy (SEM).