ELECTRONIC APPROACH TO THE PREDICTION OF PHASE-STABILITY IN CR-MO FERRITIC STEELS

A new method has been proposed for predicting the phase stability of Cr-Mo-(V-Nb) ferritic steels on the basis of an electron theory. In this method, employed is a parameter Md which is the d-orbital energy level of a transition metal element in the steel obtained by the molecular orbital calculation of bcc Fe cluster. By defining the compositional average of the parameter as MdBAR, the trend of formation is predicted of the delta-ferrite and the Laves phase (Fe2Mo) in ferritic steels. These second phases are found to be formed in the steels if the MdBAR exceeds a certain critical value. This prediction method is useful for the design and development of ferritic steels.