TY - JOUR A1 - Sestan, A. A1 - Sreekala, L. A1 - Markelj, S. A1 - Kelemen, M. A1 - Zavasnik, J. A1 - Liebscher, C. A1 - Dehm, G. A1 - Hickel, Tilmann A1 - Ceh, M. A1 - Novak, S. A1 - Jenus, P. T1 - Non-uniform He bubble formation in W/W2C composite: Experimental and ab-initio study N2 - Tungsten-tungsten carbide (W/W2C) composites are considered as possible structural materials for future nuclear fusion reactors. Here, we report on the effect of helium (He) implantation on microstructure evolution of polycrystalline W/W2C composite consolidated by field-assisted sintering technique (FAST), homogenously implanted at room temperature with 1 MeV 4He+ ions at the fluence of 8 × 1016 ions cm−2 and annealed at 1873 K for 20 minutes. Samples were analysed by scanning and transmission electron microscopy to study the presence and size of He bubbles. Monomodal He bubbles in W (30-80 nm) are limited to point defects and grain boundaries, with a considerable void denuded zone (150 nm). Bubbles do not form in W2C, but at the W|W2C interface and are considerably larger (200-400 nm). The experimental observations on He behaviour and migration in W and W2C were assessed by density functional theory (DFT) calculations, suggesting He migration and accumulation in the composite are determined by the effective He-He binding in clusters, which will give rise to decohesion. In the presence of He clusters, the decohesion of bulk W into free surfaces is energetically highly favourable but not sufficient in the W2C; hence bubbles are only observed in W grains and interfaces and not within bulk W2C. KW - Density functional theory KW - Tungsten KW - Ditungsten carbide KW - FAST KW - Helium implantation PY - 2022 U6 - https://doi.org/10.1016/j.actamat.2021.117608 VL - 226 SP - 1 EP - 11 PB - Elsevier Ltd. AN - OPUS4-54364 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -