Pinning Effect of Cerium Inclusions during Austenite Grains Growth in SS400 Steel at 1300 °C: A Combined Phase Field and Experimental Study

The pinning effect of cerium inclusions in the austenite grain growth of SS400 steel at 1300 degrees C is investigated by using a semi-empirical-simulation. Firstly, steel samples containing cerium inclusions are prepared; then the properties of inclusions are determined using SEM. In situ observation of austenite grain growth is performed by LSCM, to determine the fitting parameters of the model such as the grain mobility and the pinning parameter. These parameters are directly inserted into our phase field simulation. The time-dependent Ginzburg-Landau (TDGL) equation is implemented in our phase field model, where the effects of inclusion and grain boundary interaction are inserted as a potential term in the local free energy. The results proved that the optimal size of austenite grains can be achieved by changing the volume fraction of inclusions. In fact, by increasing the volume fraction of inclusions from 0 to 0.1, the austenite grain growth can be decreased where the boundary mobility reduces from 2.3x10(-12) m(4)/Js to 1.0x10(-12) m(4)/Js. The results also demonstrated that increasing the temperature can provide more energy for grain to overcome the inclusions' pinning force. Moreover, it was shown that the classical Zener model, Rc = 0.45 rp fi - 1, describes the pinning effect of cerium inclusions.