Austenite grain growth in alumina-forming austenitic steel

Microstructures and austenite grain growth behavior of the alumina-forming austenitic (AFA) steel subjected to normalizing and annealing at various temperatures were investigated. A modified kinetic model of austenite grain growth was constructed based on consideration of the heating history. Abnormal growth of austenite grain occurs when the temperature is increased to 1473 K, and some special large particles of the precipitates located at grain boundaries form when the sample is normalized at the temperature of 1523 K. Both NbC and NiAl precipitates are identified using routine x-ray diffraction. The fitted data based on the kinetic model used and the consideration of the heating history is in agreement with the changes in the austenite grain growth in the AFA steel even when there is abnormal grain growth. The grain growth exponents are shown to be 2.85 and 2.42 for normalizing and annealing, respectively.