Sub-zero austenite to martensite transformation in a Fe-Ni-0.6wt.%C alloy

Martensitic transformation in a model Fe-Ni-0.6wt%C alloy was investigated at sub-zero Celsius temperature. The influence of the thermal path in determining the conditions leading to the formation of martensite was studied. In the investigation, samples were austenitized and quenched, whereafter isochronal (constant cooling rate) and isothermal sub-zero Celsius treatments were applied.

Magnetometry was used for describing the overall kinetics of the transformation in terms of the Johnson-Mehl-Avrami-Kolmogorov kinetics. The evolution of the transformation was also investigated with in-situ synchrotron X-ray diffraction by evaluating austenite and martensite Bragg reflections. Also, the state of internal strain in austenite was determined.