Dynamic fracture of tungsten base heavy alloys

A recently developed short beam experimental technique has been applied to the characterization of the mode I dynamic fracture toughness (KId) of a commercial tungsten base heavy alloy (w/o-90W-7Ni-3Fe). The specimens were taken from a cylindrical swaged alloy bar and tested at a typical loading rate of the order of 10⁶ MPasqrtm/s. Three different crack orientations (one longitudinal and two radial) were investigated. The KIdvalues obtained for the three crack orientations are compared with the corresponding values obtained under quasi-static loading conditions (KIc). Our results show that the dynamic fracture of heavy alloys is both anisotropic and rate sensitive. For specimens containing radial cracks (LR, RR), the dynamic fracture toughness is higherthat its static counterpart. By contrast, for longitudinal cracks (RL), the dynamic fracture toughness is lowerthan the static one. Also, for radial cracks, both the (average) static and the dynamic fracture toughness are higher than in the longitudinal orientation. These new results about the anisotropy of the dynamic fracture toughness of the heavy alloys are reported and correlated with metallographic and fractographic examinations.