Visualization and Analysis of Variant Grouping in Continuously Cooled Low-Carbon Steel Welds

The variant grouping behavior of a simulated heat-affected zone in low-carbon steel was tracked in situ and analyzed by laser scanning confocal microscopy and electron backscatter diffraction. By visualizing the microstructural changes and crystallographic properties under rapid cooling conditions, the transition from Bain zone grouping to close-packed plane grouping was directly studied. The results were compared with those obtained under slow cooling and the link between the variant grouping behavior and the nested microstructure of lower bainite and martensite is clarified.