Dependence of ductile-to-brittle transition temperature on phosphorus grain boundary segregation for a 2.25Cr1Mo steel

Equilibrium grain boundary segregation of phosphorus in a 2.25Cr1Mo steel was studied by means of Auger electron spectroscopy (AES). After quenching from 980 °C and tempering at 650 °C, the steel samples were aged for different periods of time at 560, 520 and 480 °C, respectively, followed by AES measurements. Based on the experimental values of the equilibrium segregation levels at different temperatures along with equilibrium segregation theories, the thermodynamic parameters of segregation were evaluated. With the use of Charpy impact testing along with the AES results on phosphorus grain boundary concentration, a relationship between ductile-to-brittle transition temperature (DBTT) and phosphorus boundary concentration was established. On the basis of this relationship, predictions of the DBTT were made through predicting the grain boundary segregation of phosphorus.