Activated liquid phase sintering of W–Cu and Mo–Cu

A model for densification based on the master sintering curve concept is applied to solid-state sintering of W and Mo and to liquid-phase sintering of W–10Cu and Mo–18Cu. The effects of small additions of Ni, Co, Fe, and Pd to W–10Cu and Mo–18Cu are investigated. Separate grain growth models for solid-state and liquid-phase sintering are also applied to these systems. The model predictions are compared to experimental results to determine the effects of the activators on densification and grain growth mechanisms. Ni and Pd additions only slightly reduce the activation energy for densification, while Co and Fe have a much larger effect. The effects of Co and Fe additions on grain growth rate constants are not adequately described by consideration of their effects on the solubility of W and Mo in the liquid phase. The experimental results with Co and Fe additions are better described by a solid-state grain growth model. The effects of Co and Fe additions on densification and grain growth are consistent with enhanced diffusion through a segregated solid phase during liquid-phase sintering.