Mainz 2022 – scientific programme

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P: Fachverband Plasmaphysik

P 19: Poster II

P 19.14: Poster

Thursday, March 31, 2022, 16:00–17:30, P

Microstructural evolution of a tungsten heavy alloy during extended heat-treatments — •Philipp Sand and Armin Manhard — Max-Planck-Institute for Plasma Physik, 85748 Garching, Germany

Tungsten heavy alloy (97W-2Ni-1Fe, %wt.) is a possible candidate as plasma-facing material in future nuclear fusion devices. It exhibits a similar heat conductance at high temperature and sputter yield as pure tungsten, whilst showing an improved ductility [1] and hydrogen retention behaviour [2]. These improved properties can be attributed to its heterogenous microstructure, in which, as a consequence of the manufacturer's liquid phase sintering process, tungsten grains are embedded in a perturbating matrix of nickel and iron. In fusion devices as well as in materials testing experiments (e.g. permeation experiments) elevated temperatures for extended times might lead to grain growth or formation of intermetallic phases. Since the grain structure and tungsten-matrix interface constitution can affect the hydrogen transport, the permeation and retention behaviour might change during long-term annealing. A systematic heat treatment study has been performed with a conventional tungsten heavy alloy. Additionally, two-dimensional model systems consisting of Fe-Ni layers on W foils with identical composition where investigated to deepen the understanding of the tungsten-matrix interface. Microstructural changes are tracked with scanning electron microscopy and ion beam analysis. [1] R. Neu, et al., Fusion Eng. Des. 124 (2017) 450-454 [2] H. Maier, et al., J. Nucl. Mater 18 (2019) 245-259