The origin of the brittleness of high aluminum pearlite and the method for improving ductility

High aluminum bearing steels demonstrate poor ductility due to the presence of kappa-pearlite in the as hot-rolled condition. The addition of aluminum shifts the equilibrium eutectoid carbon concentration to a higher value. Consequently, the poor ductility of high aluminum pearlite is believed to originate from the brittleness of kappa-pearlite due to the higher fraction of brittle kappa-carbide. The spheroidization treatment of kappa-carbide is proposed and proven for the first time to improve the ductility by reducing the stress concentration at the carbide/ferrite interface and enhancing the cracking resistance of kappa-carbide due to its spheroidized morphology. (C) 2016 Published by Elsevier Ltd.