Liquid-Phase Sintering

Liquid-Phase Sintering
In many sintering processes, the intervention of a liquid phase sought to assist in the densification. The purpose is usually to enhance densification rates, achieve accelerated grain growth, or to produce specific grain boundary properties. In these materials, the distribution of the liquid and of the resulting heterophases after densification is of critical importance to the properties of the sintered body. Typically, the amount of liquid involved is small, a few volume percent, which can make precise control over the composition of the liquid difficult.
Liquid-Phase Redistribution
Capillary stress gradients can be significant when submicron liquid-phase surface curvatures are present. For a surface energy of about 1J/m 2 and a radius of curvature of 0.5 ~tm, pressure differentials within the sample can reach several MPa, sufficient to cause rapid fluid flow and particle rearrangement when the compact s effective viscosity is still relatively low. The pressure gradients will cause fluid to flow from regions with large liquid pores to regions of smaller liquid pores, and as a consequence from the surface to the interior of the compact. This principle leads to a sequential pore filling.