The effect of hot rolling on the strength and fracture toughness of 90W–7Ni3Fe tungsten heavy metal alloys

Abstract

Due to their balance of strength, ductility and toughness, liquid-phase sintered tungsten heavy metal alloys (WHAs) are considered to be an attractive alternative to monolithic polycrystalline tungsten (W) for plasma facing components. Here we explore the effect of hot rolling (HR) on the room temperature (RT) mechanical properties of a 90W–7Ni3Fe (by wt%) WHA, at different thickness reductions of 0, 62, 74 and 87%. High elastic-plastic KJm maximum load toughness for LS-oriented pre-cracked bend bars is observed in the 0 and 87% HR WHA, along with stable crack growth. In contrast, the 62 and 74% HR WHA experience elastic fracture, at much lower KIc. The opposite trend is observed in the microhardness, as well as the tensile yield and ultimate stresses, which are lowest in the 0 and 87% HR condition and highest in the 62 and 74% HR WHA. The reason for the difference in strength at 87 versus 74% HR reductions is not fully understood. However, the strength differences partially rationalize the toughness trends. Unfortunately, HR results in highly anisotropic brick-and-mortar microstructures, leading to much lower elastic KIc in the LT-orientation.