Bend stress relaxation of pure tungsten

Abstract

Tungsten is one of the candidate materials being considered for fabricating the plasma facing components (PFCs) of fusion reactors. When used in fusion reactors, PFCs are exposed to high heat loads from the fusion plasma, resulting in the PFCs being subjected to induced thermal stresses. This study focused on the creep deformation of pure tungsten under such a deformation-controlled thermal stress. Bend stress relaxation (BSR) tests were performed on specimens of as-received pure tungsten at temperatures of 600 - 1000°C for 0.1 - 1 h in vacuum. The BSR ratio decreased with an increase in the temperature, decreasing sharply in a short period of 0.1 h and then decreasing gradually. Most of the stress was relieved during the BSR test performed at 1000°C for 1 h. The activation energy of stress relaxation, calculated using the cross-cut method, was similar to that of the Peierls mechanism. This suggested that the mobility of the dislocations controls the stress relaxation mechanism. Most of the stress was relieved quickly because the activation energy of stress relaxation was relatively small. © 2013 The Japan Society of Plasma Science and Nuclear Fusion Research.