An investigation of the microporosity formation in an Al-4.1% Cu alloy casting in microgravity and in standard gravity

The microporosity formation in a vertical unidirectionally solidifying Al-4 .1%Cu alloy casting is modeled in both microgravity and standard gravity as well as in the conditions of decreased (Moon, Mars) and increased (Jupiter ) gravity. Due to the unique opportunities offered by a low-gravity environ ment (absence of metallostatic pressure and of natural convection in the so lidifying alloy) future microgravity experiments will significantly contrib ute to attaining a better physical understanding of the mechanisms of micro porosity formation. One of the aims of the present theoretical investigatio n is to predict what microporosity patterns will took like in microgravity in order to help plan a future microgravity experiment. To perform these si mulations, the authors suggest a novel three-phase model of solidification that accounts for the solid, liquid, and gas phases in the mushy zone. This model accounts for heat transfer, fluid flow, macrosegregation, and microp orosity formation in the solidifying alloy. Special attention is given to t he investigation of the influence of microporosity formation on the inverse segregation. Parametric analyses for different initial hydrogen concentrat ions and different gravity conditions are carried out.