Pearlite transformation in high carbon steels deformed in metastable austenite region

The effect of deformation in the metastable austenite region on the subsequent transformation in high carbon steels (0.70 similar to 1.09%C) at 948 similar to 848K has been investigated. The size of pearlite colonies is reduced 14 to 7 mu m in diameter depending upon the degree of deformation from 0 to 60% in the reduction of height of a cylindrical specimen. The deformation induces also the formation of proeutectoid phases (alpha or theta) in off-eutectoid steels, and the proeutectoid alpha was detected in, for instance, 0.92 mass%C steel transformed at 898K. This result reveals that the eutectoid composition at 898K is higher than 0.92 mass%C. The eutectoid point below A, temperature has been calculated from the balance equation, f(alpha).Delta G(alpha) = f(theta).Delta G(theta), where Delta G(alpha), Delta G(theta) are the driving force for alpha and theta per mole, and f(a), f(theta) are the mole fractions of alpha and theta in the pearlite. The results of the calculation are in good agreement with the experimental data, exhibiting the eutectoid composition at lower temperature is fairly higher than that of the equilibrium diagram(0.8mass%C).