The role of iron in the formation of porosity in Al-Si-Cu-based casting alloys. Part 3: A microstructural model
- Univ. of Queensland, Brisbane, Queensland (Australia)
Iron has been shown to have a significant effect on the formation of porosity and shrinkage defects in Al-Si-Cu-based foundry alloys. This is not simply a direct consequence of the physical presence of the {beta}-Al{sub 5}FeSi platelets in the microstructure, but is also due to the effect that these platelets have on the nucleation and growth of eutectic silicon. The alloy-dependent critical iron content determines when the {beta} phase first solidifies and, hence, when it can participate in the silicon nucleation event. At critical iron contents, the {beta} phase solidifies as the initial component of the ternary eutectic. However, at supercritical iron contents, the {beta} phase solidifies as the initial component of the ternary eutectic solidification begins, while, at subcritical iron contents, the {beta} phase forms as a component of the ternary eutectic only after the binary Al-Si eutectic is well established. Each of these paths of microstructural evolution leads to different variations in microstructural permeability and, hence, interdendritic feedability and porosity formation. The actual porosity-forming response to these alloy-induced microstructural changes is influenced by the solidification conditions in the casting.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 677977
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 6 Vol. 30; ISSN 1073-5623; ISSN MMTAEB
- Country of Publication:
- United States
- Language:
- English
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