Microstructure and properties of sintered tungsten heavy alloys

The microstructure and properties of liquid-phase sintered tungsten heavy alloys were studied. The structure and segregation of the impurity elements at the interfacial boundaries were examined using scanning electron microscopy (SEM) and fine-probe energy dispersive spectroscopy (EDS) microanalysis. Test results of mechanical properties are presented and correlated with fracture behavior of the liquid-phase sintered tungsten alloys. It was found that the Fe-Ni-W alloy exhibits superior properties as compared with the Cu-Ni-W alloy. The detection of copper was found across tungsten grains and matrix that could be associated with inferior properties of the Cu-Ni-W alloy as compared to the Fe-Ni-W alloy. Although the fracture was predominantly brittle in both alloys, complex fracture modes seem to be operative due to the composite microstructure of the alloys. Evidence of microsegregation was observed that also contributed primarily to the brittle failure in the alloys. The impurity elements, such as sulfur and phosphorus, were detected at the tungsten matrix and tungsten-tungsten particle boundaries.