PEARLITE TRANSFORMATION IN HIGH-CARBON ST EELS DEFORMED IN METASTABLEAUSTENITE REGION

The effect of deformation in the metastable austenite region on the su bsequent transformation in high carbon steels (0.70 similar to 1.09%C) at 948 similar to 848K has been investigated. The size of pearlite co lonies is reduced 14 to 7 mu m in diameter depending upon the degree o f deformation from 0 to 60% in the reduction of height of a cylindrica l 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 h igher than 0.92 mass%C. The eutectoid point below A, temperature has b een calculated from the balance equation, f(alpha).Delta G(alpha) = f( theta).Delta G(theta), where Delta G(alpha), Delta G(theta) are the dr iving force for alpha and theta per mole, and f(a), f(theta) are the m ole fractions of alpha and theta in the pearlite. The results of the c alculation are in good agreement with the experimental data, exhibitin g the eutectoid composition at lower temperature is fairly higher than that of the equilibrium diagram(0.8mass%C).