Damage behaviors in microstructures and mechanical properties of pure tungsten induced by repetitive thermal loads

Abstract

Damage behaviors of ITER grade tungsten (W) induced by repetitive thermal loads have been investigated using an electron beam device EBMP-30. The metallographic observation, backscattered electron scanning electron microscopy, electron backscattered diffraction, atomic force microscopy analysis and tensile tests were carried out after the repetitive heat loads. Results indicate that there are negligible effects on the microstructures, surface morphologies and mechanical properties with the absorbed power densities (APD) lower than 10 MW/m 2 . While serious damages including the severe surface roughness with protruding structures along grain boundaries, and significant grains coarsening with the evolution of the grain shape occur undesirably due to the full recrystallization during the repetitive 30 MW/m 2 heat loads. Furthermore, after exposed to an APD of 30 MW/m 2 with 50 heat loads, the tensile properties deteriorate dramatically, resulting in a limited ultimate tensile strength of only 328 MPa and even a zero total elongation at 300 °C. The relationships between the thermal loads, microstructures evolution and degradation of mechanical properties have been analyzed.