Molecular dynamics simulations of densification processes in nanocrystalline materials

Molecular dynamics computer simulations were employed to investigate the dynamic processes of diffusion, grain growth, sintering, and consolidation in nanocrystalline copper (n-Cu). At room temperature, fully dense n-Cu was found to be stable. At 1100 K, a large fraction of atoms in the n-Cu became amorphous which provides a new mechanism of grain growth and recrystallization. Atomic mobility in dense n-Cu decreased with time as the grain boundaries relaxed. The initial configurations of the grains were shown to have a strong influence on pressureless sintering. Both hydrostatic pressure and uniaxial stress loading accelerated the process of densification on porous n-Cu. The latter, however, was found more efficient due to grain boundary sliding.