H. Combeau et al., MODELING OF MICROPOROSITY FORMATION IN ALUMINUM-ALLOYS CASTINGS, Materials science & engineering. A, Structural materials: properties, microstructure and processing, 173(1-2), 1993, pp. 155-159
The solidification of Al-7wt.%Si alloy in sand mold geometries has bee
n simulated using a 2D-finite volumes model which takes full account o
f coupled heat, mass and momentum transport phenomena. The shrinkage b
oundary condition used in this model is detailed, and results of the s
imulation are presented in terms of pressure drops which are Viewed so
metimes as one of the major causes of micropore formation in aluminium
castings. Solidification of plates of different thicknesses in sand m
old has been investigated. Calculations give a maximum absolute pressu
re drop of 27 000 Pa in the 7.5 mm thick casting whereas this maximum
is only 300 Pa in the 30 mm thick casting. Considering the condition o
f microporosity formation, these results point out that pressure drops
are far too low to account for the formation of micropores which are
observed experimentally. Hydrogen segregation has to be considered and
integrated in a model to give a good prediction of micropore appearan
ce.