A micromechanical model for the initial rearrangement stage of liquid phase sintering

A constitutive model for powders in the initial rearrangement stage of liquid phase sintering (LPS), where capillary force is the driving force for densification, is developed in this paper, The formulation is based on certain theories in micromechanics of granular materials (see Mehrabadi et al., 1992a; Mehrabadi et al., 1992b; Nemat-Nasser and Mehrabadi, 1983; Nemat-Nasser and Mehrabadi, 1984; Christoffersen et al., 1981). The anisotropic mechanical behavior of powder system is analyzed by considering the behavior of interparticle force and fabric which is represented by the distribution of contact normals. The proposed model is used to determine the dependence of the overall volume change on such factors as local liquid volume, uniformity of liquid distribution, contact angle, initial particle distance, initial confining pressure, particle size and viscosity, The numerical and theoretical analyses in this paper indicate that small particle size, small contact angle, low viscosity, even distribution of liquid phase and loose green powder mass enhance the amount of volume change in the initial stage of LPS. It is also found that a higher confining pressure increases the densification rate but it lowers the amount of net volume shrinkage at the end of the initial stage, The anisotropic behavior of the sample is analyzed by studying the interparticle force change and fabric change during the sintering.