Abstract
The mechanism by which iron causes casting defects in the AA309 (Al-5 pct Si-1.2 pct Cu-0.5 pct Mg) may be related to the solidification sequence of the alloy. Superimposing calculated segregation lines on the liquidus projection of the ternary Al-Si-Fe phase diagram suggests that porosity is minimized at a critical iron content when solidification proceeds directly from the primary field to the ternary Al-Si-βAl5FeSi eutectic point. Solidification via the binary Al-βAl5FeSi eutectic is detrimental to casting integrity. This hypothesis was tested by comparing the critical iron content observed in the standard AA309 alloy to that of a high-silicon (10 pct Si) variant of this alloy.
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Taylor, J.A., Schaffer, G.B. & StJohn, D.H. The role of iron in the formation of porosity in Al-Si-Cu-based casting alloys: Part II. A phase-diagram approach. Metall Mater Trans A 30, 1651–1655 (1999). https://doi.org/10.1007/s11661-999-0102-0
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DOI: https://doi.org/10.1007/s11661-999-0102-0