Effect of grain boundary sliding on shear viscosity and viscous Poisson’s ratio in macroscopic shrinkage during sintering

Macroscopic quantities such as strain rate and viscosity during sintering can be obtained from the microscopic motion of particles normal and tangential to grain boundaries. When grain boundary diffusion is the dominant transport mechanism of sintering, the viscous shear modulus and viscous Poisson’s ratios are dependent on the grain boundary diffusion coefficient and the microscopic viscosity of grain boundary sliding. The microscopic viscosity is not constant, varying with microstructural evolution during sintering. The viscous Poisson’s ratio decreases with increasing microscopic viscosity, and increases with relative density. The viscous Poisson’s ratio for a given relative density is also dependent on the local configuration and the ratio of grain boundary energy to surface energy.