Phase Translation in Hadfield Steel Isothermally Heated at 500℃ after Solution Treatment

概要

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Hadfield steels isothermally heated at some temperatures undergo precipitations of grain boundary carbides. In steels with, precipitates grown up to a large amount, γ transformed into ε at about room temperature by cooling and theε-phase was present with carbides and α-phase. The equilibrium phases in a Hadfield steel at room temperature were reported to consist of α+carbide, but the process of phase translation leading to the equilibrium is not yet completely known. In the present work standard Hadfield steels of chemical composition of 13.7% manganese and 1.2% carbon and isothermally heated at 500℃ after solution treatment were studied mainly dilatometrically and magnetically. At 500℃, as well known, carbides first precipitated from γ-phase then γ transformed to carbide+α-phase, but it took a very long time to attain the equilibrium state. While in lower temperature it may be supposed that the γ-phase transformed in the following sequence : γ+carbide→γ+ε+carbide→γ+ε+α+carbide→+ε+α+carbide and finally to the equilibrium (α+carbide) in the long years. Thusε-phase in Hadfield steel is apparently metastable appearing only in phase transformation process to be equilibrium.
東北大学の論文