Effects of Rare Earth on Austenite–Ferrite Phase Transformation in a Low-Carbon Fe–C Alloy

The influence of rare earth (RE) elements on austenite–ferrite phase transformation in Fe–0.14%C alloy has been investigated by in situ observing the nucleation, growth and morphology of ferrite using high temperature laser scanning confocal microscopy, and controlled atmosphere decarburization experiments. It is found that under the low-oxygen condition in steel, trace RE addition can significantly influence the nucleation, morphology and growth of ferrite in Fe–0.14%C alloy by the combined effects of RE slowing down the carbon diffusion and decreasing grain boundary energy by segregating at grain boundaries. This research provides evidences of adjusting the phase transformation and improving the mechanical properties of steels by RE addition.