Pearlite Transformation in High Carbon Steels Deformed in Metastable Austenite Region

Abstract

The effect of deformation in the metastable austenite region on the subsequent transformation in high carbon steels (0.701.09%C) at 948848K has been investigated.
The size of pearlite colonies is reduced 14 to 7μm 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 (α, or θ) in off-eutectoid steels, and the proeutectoid α, 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 A₁ temperature has been calculated from the balance equation, f_α·ΔG^α=f_θ·ΔG^θ, where ΔG^α, ΔG^θ are the driving force for α and θper mole, and f_α, f_θ are the mole fractions ofα and θ 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).