Influence of Particle Arrangement on Sintering.
Annual rept. 1 Jul-30 Nov 84,
ROCKWELL INTERNATIONAL THOUSAND OAKS CA SCIENCE CENTER
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The change in free energy of identical cylinders arranged in rings to enclose one pore shows that the pore can either shrink to an equilibrium size or disappear depending on the number of cylinders coordinating the pore and the grain boundary energy to surface energy ratio as expressed by the dihedral angle. The same result is obtained for symmetric, closed arrays of spheres rings and polyhedral. The shrinkage and strain rates of these closed arrays depends on both the dihedral angle and pores coordination number viz, arrays with a lower coordination number. When arrays with different coordination numbers are packed together, the differential shrinkage strain and strain rate between the arrays. The movement of particles during initial mass transport, commonly termed rearrangement, is due in part to differential strains and strain rates between particle clusters. Longer range transparticle mass transport gives rise to grain growth within an array. Grain growth in a powder compact is driven by the difference in external surface curvature between particles within the different arrays. Grain growth will lower a pores coordination number and thus will overcome the thermodynamic barrier to pore closure. Additional keywords Particle arrays Densification.
- Manufacturing and Industrial Engineering and Control of Production Systems