Microstructure and bubble formation of Al-K-Si doped tungsten prepared by spark plasma sintering

Dense potassium-doped tungsten (W-K) ingots with homogeneously dispersed nanoscaled bubbles were fabricated by spark plasma sintering (SPS) using Al-K-Si (AKS) doped tungsten powder. Parameters such as sintering temperature, holding time and sintering pressure were considered to tune the grain size, density, microhardness, bubble formation and impurity contents. In addition, a two-step sintering scheme was designed to reduce Al/Si impurity contents and enhance the density. The sample prepared by the two-step sintering scheme displays both inter- and intra-granular nanocomposites, which is expected to have better creep resistance, high bending strength and fracture toughness. Potassium was detected inside the bubbles, determining the crucial role in the bubble formation process, and thus leading to compatible properties as plasma-facing material.