Isothermal martensitic transformation in Fe-Ni and Fe-Ni-C alloys at subzero temperatures

Abstract

A survey of experimental work on the isothermal martensitic transformation in the presence of prior martensite is given in Fe-Ni and Fe-Ni-C alloys having subzero Ms (Mb) temperatures. Low temperature dilatometric measurements are correlated with internal friction measurements in the 5 to 200 K temperature range. This study will show that this transformation can be discussed in terms ofC-curve behavior as in Fe-Ni-Mn alloys. Nevertheless, in Fe-Ni and Fe-Ni-C alloys internal stresses created by the austenite-to-martensite transformation during cooling play an important part in the development of the isothermal transformation. Furthermore, internal friction is shown to be proportional to expansivity thus indicating that the internal friction technique can be applied successfully for the study of phase transformations.