Using a finite element model for simulating dendritic solidification of multicomponent-alloy castings, the pressure and redistribution of dissolved hydrogen during solidification and cooling in A356 aluminum casting alloy were calculated. The model solves the conservation equations of mass, momentum, energy, each alloy component, and hydrogen. By solving the redistribution of the concentration of hydrogen and comparing its Sievert's pressure with the local pressure within the alloy, the model predicts regions of possible formation of intergranular porosity. Calculations were performed on the equiaxed alloy (A356) cast into a bottom-cooled plate for which casting conditions and microporosity were known. The potential to form the microporosity was analyzed with respect to the initial concentration of hydrogen and the final grain size. Based on the simulations, pore formation is more sensitive to the initial hydrogen concentration than it is to the grain size of the alloy. It was found that the predicted results agreed qualitatively with empirical results determined for the same alloy and casting conditions. In its present form as a work-in-progress, the model calculates the pressure of hydrogen gas and compares it to the intergranular pressure to decide whether porosity forms during cooling and solidification of castings. Features to account for pore volume and pore number distributions will be added to the model in the near future.
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