The stabilization of retained austenite after partial transformation to martensite has been investigated using 1.12 % C, 4.98 % Ni steel. The stabilization degree was expressed by the temperature lag θ of transformation point or the amount of the stabilized austenite, δ. It has been observed that the temperature lag θ is a function of aging time. It has been found that the recovery of martensite transformation occurred during subsequent cooling after aging in the early stage of stabilization, but did not occur in the last stage of it. Accordingly the correlation between θ and δ is not a linear relation. The stabilization proceeded very rapidly when the previously transformed martensite increases to more than 65 per cent
