EFFECT OF RHENIUM ADDITION ON FRACTURE-TOUGHNESS OF TUNGSTEN AT ELEVATED-TEMPERATURES

Fracture toughness tests of tungsten and tungsten-rhenium alloy specim ens were carried out at elevated temperatures. Temperature dependence of fracture toughness and effect of rhenium content on fracture toughn ess were investigated. Although fracture toughnesses of three kinds of specimens with rhenium contents of 0, 5 and 10 wt % were almost ident ical at room temperature, fracture toughness at elevated temperatures increased with increasing rhenium content. The brittle-ductile transit ion, similar to steels, and subsequent transition of the fracture mode from ductile dimple to intergranular were observed for all three kind s of specimens. With increasing rhenium content, the transition temper atures increased. A significant grain growth was found, not for tungst en-rhenium alloy specimens, but for a tungsten specimen without rheniu m in a temperature range higher than the recrystallizing temperature, which resulted in transition of the fracture mode from dimple to inter granular.