Role of solid-state skeletal sintering during processing of Mo-Cu composites

Mo-Cu composites with Mo contents up to 85 wt pet can be processed by eithe r infiltration of a presintered Mo skeleton with liquid Cu or by liquid-pha se sintering of mi:ted Mo and Cu powders. For both cases, the effects of pa rticle size, sintering temperature, and sintering time on densification and microstructural evolution are compared. The effects of transition metal ad ditions on the densification of Mo-Cu are also investigated. The liquid-pha se sintering densification rate of Mo-Cu is much slower than in traditional liquid-phase sintering and is similar to the solid-state densification rat e of elemental Mo. Furthermore, the poor densification behavior and absence of slumping for compositions up to 50 vol pet Cu indicate that the high di hedral angle of the Mo-Cu system stabilizes the formation of a rigid Mo ske leton during liquid-phase sintering. Results from a computer simulation tha t takes into account mass transport via both solid-state and liquid-phase m echanisms show that the solubility of Mo in Cu is sufficient for rapid dens ification, but confirm that the sintering behavior of Mo-20 vol pet Cu is b est described by solid-state skeletal sintering. In this case, the liquid p hase promotes microstructural coarsening by solution reprecipitation but co ntributes Little to densification because of the rigid Mo skeleton.