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 either infiltration of a presintered Mo skeleton with liquid Cu or by liquid-phase sintering of mi:ted Mo and Cu powders. For both cases, the effects of particle size, sintering temperature, and sintering time on densification and microstructural evolution are compared. The effects of transition metal additions on the densification of Mo-Cu are also investigated. The liquid-phase sintering densification rate of Mo-Cu is much slower than in traditional liquid-phase sintering and is similar to the solid-state densification rate of elemental Mo. Furthermore, the poor densification behavior and absence of slumping for compositions up to 50 vol pet Cu indicate that the high dihedral angle of the Mo-Cu system stabilizes the formation of a rigid Mo skeleton during liquid-phase sintering. Results from a computer simulation that takes into account mass transport via both solid-state and liquid-phase mechanisms show that the solubility of Mo in Cu is sufficient for rapid densification, but confirm that the sintering behavior of Mo-20 vol pet Cu is best described by solid-state skeletal sintering. In this case, the liquid phase promotes microstructural coarsening by solution reprecipitation but contributes Little to densification because of the rigid Mo skeleton.