Three-Dimensional Morphology and Growth Behavior of Ferrite Allotriomorphs Formed at Grain Boundary Edges

Three-dimensional morphology of ferrite allotriomorphs nucleated at grain boundary edges in low carbon steel was revealed by means of serial sectioning in conjunction with computer-aided three-dimensional reconstruction techniques. The typical morphology of them was of an elongated triangular pyramid. The length, width and thickness of ferrite allotriomorphs were measured on the basis of three-dimensional reconstructed images. The aspect ratio (length/width) of them was 4.5 on an average and scattered from 3 to 6. The measured sizes were smaller than calculated ones, which was probably attributed to solute drag-like effect of manganese in the alloy.