Mechanical properties and microstructural evolution of Mo-Co-co-strengthened W-Ni-Fe alloys by spark plasma sintering

Fine-grained tungsten (W) alloys with excellent properties were prepared by using advanced spark plasma sintering (SPS) and combining with Mo and Co multi-element alloy strengthening technology. The relative density of W alloy increases from 90.68% to 96.22% when it is sintered at a low temperature range of 1000 °C-1225 °C. The W alloy prepared at a low sintering temperature exhibits high hardness and low bending strength. As sintering temperature increases, the hardness of the alloy gradually decreases and the bending strength increases. The simultaneous addition of Mo/Co elements can decrease the liquid-phase sintering temperature of alloys. The prepared W alloy is close to full densification and the W grains are nearly spherical when sintering temperature is increased to 1250 °C. This observation reveals the characteristics of sufficient liquid-phase sintering. The hardness and bending strength of the alloys at 1250 °C are simultaneously increased relative to those sintered at 1225 °C because of the sufficient liquid-phase sintering and Mo-Co co-strengthening. Therefore, these alloys exhibit optimum mechanical properties. The ductile tearing characteristics of binding phase can be seen obviously on the alloy fracture surface.