Effect of helium ion irradiation on tungsten recrystallization

WG Guo and SW Wang and K Xu and YD Zhu and XX Wang and L Cheng and Y Yuan and EG Fu and LP Guo and G De Temmerman and GH Lu, PHYSICA SCRIPTA, T171, 014004 (2020).

DOI: 10.1088/1402-4896/ab36d8

Understanding of the recrystallization kinetics of tungsten plasma- facing materials under fusion-related conditions is of crucial importance to estimate the material lifetime and the evolution of the material properties such as strength/hardness and thermal shock resistance. High-energy helium ion irradiation was used to study the effect of helium produced by neutron irradiation and tritium decay on tungsten recrystallization. Results indicate that low-concentration helium at about 40 appm retards the tungsten recrystallization without pronounced helium bubble formation. For a higher concentration helium, peak value at about 7700 appm, substantial subgrains and recrystallized nuclei formed but the grain boundary migration was strongly impeded by helium clusters/bubbles, eventually causing grain engulfment. The impurity drag effect of helium atoms on grain boundary migration is considered to be the dominant mechanism causing the retarding effect, as demonstrated by molecular dynamics simulations. This work indicates a potentially strong retarded recrystallization of tungsten, taking into account the bulk helium production during fusion plasma operation.

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