Effect of initial grain size on sintering trajectories

Sintering trajectories were simulated for different initial grain sizes assuming grain-boundary diffusion as densification mechanism and either pore drag or intrinsic grain-boundary mobility as grain growth mechanisms. Computation of comparable sintering trajectories for initial grain sizes between 10 nm and 250 nm necessitated an adjustment of the isothermal sintering temperature. Conditions where one of the two coarsening mechanisms prevails were determined and shown to depend on density, grain size, and the ratio S of the rate constants related to the two coarsening mechanisms, but little on the dihedral angle. All computed sintering trajectories have a common shape, being very flat at low densities and exhibiting most grain growth in the last 5% of densification before reaching their end-point density. Depending on the difference between the activation energies related to the dominant densification and coarsening mechanisms, a reduction in grain size might be beneficial for densification.