Effect of initial grain size on sintering trajectories

Sintering trajectories were simulated for different initial grain sizes ass uming grain-boundary diffusion as densification mechanism and either pore d rag or intrinsic grain-boundary mobility as grain growth mechanisms. Comput ation of comparable sintering trajectories for initial grain sizes between 10 mm and 250 nm necessitated an adjustment of the isothermal sintering tem perature. Conditions where one of the two coarsening mechanisms prevails we re determined and shown to depend on density, grain size, and the ratio S o f the rate constants related to the two coarsening mechanisms, but little o n the dihedral angle. All computed sintering trajectories have a common sha pe, being very Aat at low densities and exhibiting most grain growth in the last 5% of densification before reaching their end-point density. Dependin g on the difference between the activation energies related to the dominant densification and coarsening mechanisms, a reduction in grain size might b e beneficial for densification. (C) 2000 Acta Metallurgica Inc. Published b y Elsevier Science Ltd. All rights reserved.