A comprehensive model of ordered porosity formation

The model presented in this paper considers heat transfer, gas diffusion and simultaneous growth of solid and gas fractions in an ordered porosity ingot. Special attention is paid to the gas pore nucleation. The diffusion boundary layer ahead of the solid/liquid interface is analysed with respect to the diffusion process and structure formation, both controlled by external gas pressure, solidification velocity and gas fluxes between solid, liquid and pores. The relationships between processing parameters and structure characteristics are described. How the porosity structure is affected by the size of gas nuclei and the number of nucleation sites on the solid/melt interface is analysed.