On the control of the liquid-phase distribution in multi-material assemblies processed by liquid-phase sintering

Proper control of composition gradients in components processed by liquid-phase sintering requires the control of the migration of the liquid phase during sintering. A model considering isotropic interface energies has been developed for expressing the variation of the solid-liquid interface area with liquid volume fraction during the final stage of liquid-phase sintering (i.e. when residual porosity has disappeared). The model allows the computation of the driving forces for shape accommodation as a function of the dihedral angle Psi, liquid volume fraction, u, particle volume, V-p and average particle coordination, n(c). It particularly enlightens the coupling between the effects of Psi and of n(c). The model allows a new insight into the control of microstructural evolution during liquid-phase sintering of assemblies of dual-phase materials with different average particle size. Taking Psi = 0 degrees for the WC-Co system, the model was found to predict with a good accuracy the distribution of Co at equilibrium in assemblies made by heat-treating at 1400 degrees C under protective atmosphere stacks of cylinders of WC-Co cermets differing in mean WC particle size and cobalt content. (C) 2008 Elsevier B.V. All rights reserved