Austenite-to-ferrite transformation in low alloy steels during thermomechanically controlled process studied by in situ neutron diffraction

Microstructural evolution during the ferrite transformation in two low alloy steels was investigated in situ by neutron diffraction. The transformation kinetics determined from the neutron diffraction profiles were well consistent with those measured from the metallographic microstructures, and the carbon enrichment in austenite during the ferrite transformation was confirmed by the changes in (1 1 1) lattice plane spacing of austenite. The deformed and non-deformed austenite microstructures were found to exhibit distinguishable shape difference in their transition curves. The niobium addition and austenite deformation were demonstrated to promote the ferrite transformation.