Bale, Philip (2012)
M.Res. thesis, University of Birmingham.
A program of research was conducted to evaluate the feeding behaviour of a new highly grain refined Al-4%Cu alloy, A20X, and reflect its castability within the software package MAGMASOFT for process development. A20X alloy and two similar Al-4%Cu alloys (grain refined and ingot A201) with varying levels of grain refinement were assessed quantitatively in terms of centreline porosity development in a simple geometric shaped casting (keelblock). A MAGMASOFT solidification model was calibrated experimentally to verify boundary conditions and a material database developed to accurately reflect the A20X alloys solidification behaviour based on measurement of thermophysical properties. The model was calibrated using volume fraction porosity measurements and the porosity module function (feeding effectiveness). It was found that A20X alloy exhibited significantly reduced porosity along the casting centreline (0.48%) when compared with both the grain refined A201 alloy (0.97%) and ingot A201 alloy (1.48%). This effect was due primarily to the higher levels of Ti and B present producing a fully globular microstructure. The A20X model was calibrated at a feeding effectiveness value of 93% and predicts better global porosity levels than the MAGMASOFT Al-4%Cu model, but was unable to resolve local distribution patterns because MAGMASOFT is unable to account for the heterogeneous nucleation of porosity.
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