Crystallization behavior of iron-containing intermetallic compounds in 319 aluminum alloy
- Univ. du Quebec, Chicoutimi (Canada)
- McGill Univ., Montreal, Quebec (Canada). Dept. of Mining and Metallurgical Engineering
The crystallization behavior of iron-containing intermetallic compounds in industrial grade 319 aluminum alloy has been investigated by means of thermal analysis and metallography. In the absence of manganese, the iron compound crystallizes in the [beta] phase, at all cooling rates ranging from 0.1 C/s to 20 C/s under normal casting temperatures (750 C). However, when the melt is superheated to a high temperature (about 200 to 300 degrees above the liquidus temperature), the iron compound crystallizes in the [alpha] phase at high cooling rates. This is due to the fact that [gamma] alumina, which forms at low melt temperatures ([<=]750 C), acts as a nucleus for crystallization of [beta] phase. When the melt is superheated to high temperatures ([>=] 850 C), the [gamma] alumina transforms to [alpha] alumina. This is a poor nucleus for the [beta]-phase crystallization, and as a result, [alpha] phase forms. The importance of nucleation and growth undercooling for the crystallization of iron compounds is highlighted. In the presence of manganese, the iron compound crystallizes in [alpha] phase at low cooling rates and in both the [alpha] and [beta] phases at high cooling rates. This reverse crystallization behavior is explained in terms of phase diagram relationships.
- OSTI ID:
- 6983504
- Journal Information:
- Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Vol. 25:8; ISSN 0360-2133
- Country of Publication:
- United States
- Language:
- English
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