A model for the formation of interdendritic cavities from pores pre-existing in the melt

A model has been developed describing the growth of pores in a dendritic ne twork. It is assumed that the growing pores originate from pores (bubbles) that pre-exist in the melt and contain soluble and insoluble gases. The gro wth of an individual pore is tracked in the model as the cellular/dendritic solidification front passes. As long as the pore surface is not in contact with the solid phase, the pore maintains its spherical shape during coolin g/solidification. When the pore size reaches the width of the interdendriti c/intercellular channel, it assumes the shape of the channel, pushing the r emaining liquid out. In a systematic study, the initial conditions for the numerical calculations are varied in order to investigate the influence of different processing parameters on final porosity and length of pores. inte rfacial tension and initial pore size are shown to change the simulation re sults only slightly. Solidification shrinkage is shown to have no effect on amount and shape of micropores. With decreasing temperature gradient, poro sity increases drastically. Pore elongation is mainly a function of tempera ture gradient and density of pre-existing pores: pronounced temperature gra dients and low initial pore density favour the formation of highly elongate d pores.