Solidification from highly undercooled iron base alloys and formation of metastable phases

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Non-equilibrium crystals and amorphous materials produced by rapid solidification processings have developed and are growing to new advanced materials. Their characteristics largely depend on the rapid solidification variables and therefore it is very important to understand the correlation between processing and controlling of structures and properties. Liquid metals are highly undercooled in rapid cooling prior to crystallization. To simulate the rapid solidification, it is a basic problem to know to what extent the maximum undercooling is achieved and what phase is formed. In this research, relationship between composition,undercooling and phase formed is considered for iron base alloys containing semi-metals. In Fe-B alloys, metastable eutectic ( Fe+FeB ) is first observed. In Fe-P alloys, metastable eutectic are also confirmed. In Fe-C alloys, metastable <delta> phase is formed in the range of the hyperperitectic composition of 1.2%. These metastable phases can be explained by the thermodynamic consideration for undercooling. In Fe-Si-B alloys, large undercooling range for primary FeB is consistent with the formation range of amorphous.