Ultra-refinement of hypereutectoid steel during deformation of undercooled austenite

The microstructure evolution of a hypereutectoid steel(0.97%C)during deformation of undercooled austenite was investigated by uniaxial hot compression simulation experiment.The results indicate that the proeutectoid network carbides were restrained by deformation of undercooled austenite and only pearlite was formed by dynamic transformation of undercooled austenite.Lamellar pearlite was spheroidized dynamically by hot deformation,resulting in the formation of ultrafine(α+θ)microduplex microstructures.The increase of deformation temperature,leading to the decrease of the degree of un- dercooling,has the retarding effect on dynamic transformation of undercooled austenite.The decrease of strain rate,leading to the prolonging of the deformation time,was beneficial to dynamic transformation of undercooled austentite and dynamic spheroidization of pearlite,but the resulted ultrafine microduplex microstructures was coarser.