Solid-state spreading and sintering of multiphase materials

Sintering of composite materials consisting of a major metallic (or metal-like) refractory phase and a minor metallic binder phase may occur in the solid state, below melting temperature of the metallic binder or the eutectic. The mechanisms and kinetics of solid-state spreading and sintering in such systems as W–Cu–Ni and WC–Co are analysed from experimental results and models and discussed in relation to thermodynamics and interfacial characteristics of the different systems. Microstructural characterization gives evidence of non-uniform spreading and densification, with sequential pore filling by the binder phase and a gradual densification of agglomerates of increasing size. Spreading-assisted particle rearrangement is responsible for the macroscopic shrinkage, but its efficiency depends on the system and on the sintering process. The role of the refractory particle skeleton is particularly emphasized.