Compaction and sintering effects on scaling law of permeability-porosity relation of powder materials

Abstract

Analysis and understanding of the permeability-porosity relationship of powder materials by cold compaction and solid-state hot sintering is very important for material design and optimization. This work presents a pore-scale numerical framework, including a discrete element method for powder cold compaction, a cellular automata algorithm with curvature-driving redistribution for solid-state hot sintering and a lattice Boltzmann method for fluid flow simulation, to study the permeability-porosity relationship of materials by cold compaction and solid-state hot sintering processes. The results show that the cubic scaling law always holds for the porous materials by cold compaction, while the hot sintering process decreases the permeability dramatically at low porosity. An exponential decay function has been proposed as a correction factor to the permeability-porosity relationship of materials by compaction & sintering processes, which predicts the permeability asymptotically approaching to the cubic scaling law at high porosity while agreeing well with both numerical and experimental data at low porosity. The microstructure evolution analysis shows that the small pores that connect large pores may vanish by sintering, which causes the remarkable permeability decrease at low porosity. The excellent agreements between the numerical predictions and the experimental measurements suggest that the proposed numerical framework provides a powerful tool for analysis and optimization of material designs.