科研之友
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摘要
Microstructures in X80 line pipe were classified by SEM analysis. The experimental results showed that the microstructures in X 80 line pipe steels were complicated consisting of polygonal ferrite, bainite and acicular ferrite. Orientation relation within acicular ferrite was investigated systematically by means of EBSD-OIM. The sub-structures were observed maximum in acicular ferrite which gives high strength and high toughness to line pipe steels. The K-S orientation relation was generally observed between acicular ferrite and austenite during phase transformation. The low energy CSL boundary characterized by Sigma 3 orientation relation according to Brandon criterion appeared with higher probability, which was benefit to improve the mechanical properties of line pipe steels. The orientations or texture of initial austenite grains could be deduced based on the Sigma 3 orientation relationship of acicular ferrite variants.
