Influence of cold rolling on the fatigue crack growth behavior of tungsten

Abstract

The influence of cold rolling on the fatigue crack growth (FCG) behavior of pure tungsten was investigated. For that tungsten sheets with three different thicknesses (2 mm, 1 mm and 100 μm) corresponding to different degrees of deformation were selected to prepare compact-tension (CT) and single edge notched tension (SENT) specimens. To account for orientation influences the crack propagation direction parallel, perpendicular and under 45° to the rolling direction was investigated. It could be shown that a pronounced cyclic R-curve behavior evolves, leading to relatively high thresholds of stress intensity factor range ΔKth, even at high load ratios. Furthermore, for the smallest grain size a pronounced anisotropy of the FCG behavior was observed where the crack growth direction perpendicular to the rolling direction exhibits the highest ΔKth and the lowest crack growth-rates. Especially the tungsten foils with 100 μm thickness showed stable crack growth with a pronounced Paris-regime. As a consequence, cold rolled tungsten qualifies as a fatigue resistant laminate material applicable for future structural applications in harsh environments.