Abnormal nodular ferrite (NF) with vanadium carbide (VC) interphase precipitation was observed in a vanadium-microalloyed low carbon steel. The NF is characterized as a structure with a high density of low-angle boundaries, having an irrational ferrite/austenite orientation relationship (OR) with angular deviation of 15-30 ° from the exact Kurdjumov-Sachs OR with its neighboring austenite grain into which it grows. The growth of NF is substantially faster than that of normal grain boundary ferrite in the same alloy. Even in one single NF, the formation of multiple variants of VC interphase precipitation was confirmed, each of which was bordered by low-angle boundaries.
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