Evolution of carbon and oxygen concentration in tungsten prepared by field assisted sintering and its effect on ductility

Abstract

Good thermal conductivity, high-temperature strength and low tritium retention favour the use of tungsten as a plasma facing material for fusion reactors. However, high ductile-to-brittle transition temperature (DBTT) of tungsten limits its application. The most viable way of industrial-scale tungsten production is powder metallurgy. Conventional methods use high temperatures and long dwell times. However, this can degrade the mechanical properties of tungsten due to excessive grain growth. Therefore, new sintering techniques and unconventional sintering parameters are explored. The aim is to achieve less demanding single step processing method with the potential to improve mechanical properties. In this study, pure tungsten samples were prepared by Field Assisted Sintering using different dwell times, atmospheres and foils. The effect of the parameters on the impurity concentration was analysed and the mechanical behaviour was evaluated using stress-strain analysis. Significant improvement in mechanical performance has been reached for short dwell times (2 min) and vacuum or Ar + H2 atmosphere.