A mechanism of porosity distribution in A356 aluminum alloy castings

Abstract

The problem of porosity and shrinkage defects in metal casting is complex. Over the years there have been debates on the mechanisms responsible for their formation. In this study A356 aluminum alloy with different hydrogen contents in the melts were cast in a permanent mold and the porosity content and thermal parameters were measured. A simple mechanism was proposed to explain the porosity distribution in the casting. In the mechanism both the roles of interdendritic feeding resistance by Darcy's law and kinetic hydrogen diffusion into the pore are involved. By differentiating one factor in the model, and comparing the prediction with the experimental data, the study suggests that both factors should be taken into consideration to satisfactorily explain the porosity distribution in the castings.