Abstract
Iron intermetallic phases and their distribution in DC cast ingots have a significant impact on the quality of final sheet products. However, accurate identification and quantification of iron intermetallic phases in the cast ingots are a great challenge due to their small size and similar chemical composition. In this study, the phase identification and quantitative analysis of the volume fraction were performed using the combination of SEM, EBSD, EDS and image analysis. The results showed that four types of iron intermetallic phases (AlmFe, α-AlFeSi, Al3Fe and Al6Fe) exist in AA 5657 cast ingots. Using the deep-etching technique, typical morphologies of iron intermetallic phases were revealed. It was found that AlmFe was the dominant phase in the region near the cast surface, while Al3Fe became predominant towards the ingot center. Between the cast surface and the ingot center, α-AlFeSi changed into the leading phase. The mechanism for the phase selection and transition in cast ingots has been discussed.
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