Activated sintering mechanisms of W-pre-alloy bronze composites by Fe and Co activators addition

In this study, the effects of 1-3 wt. % Fe and Co additions on the sintering of W40-80 wt. %-pre-alloy bronze compacts were examined. The compacts were sintered isothermally at temperatures ranging from 920°C to 1100°C for 3hrs. Relative sintered densities in the range of 65-90% were achieved. The gain in sintered density due to activators addition was 5-15%. The sintering activation effects started at 900°C. SEM, XRD and EDX tests proved that Fe and Corich crystalline interboundary layers completely wet the tungsten grain boundaries in the solid state and act as short-circuit diffusion path for mass transportation. This outcome seems to follow the classical activated sintering model and comes in contrast with some other recently proposed models, whereby a detected nanometer-thick, activator-enriched disordered film at W grain boundary is considered fully responsible for the solid-state activated sintering.