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利用电镜研究了４０ＣｒＭｎ２Ｓｉ２Ｍｏ铸钢准下贝氏体中变态组织及精细结构。观察到交叉型、中脊型类马氏体形貌贝氏体，发现贝氏体中脊中有大量层错。贝氏体交叉的形成是切变应力—应变诱发贝氏体转变引起，中脊是贝氏体相变初期切变机制快速形核与长大的结果。中脊中层错的存在，为贝氏体相变过程存在切变机制提供了依据。
The abnormal microstructure and fine structure of 40CrMn2Si2Mo cast lower quasi-lower bainite were studied by electron microscope. Cross-shaped, mid-ridge-type martensitic bainite was observed and a large number of faults were found in the mid-bainite ridge. The formation of bainite crossover is caused by shear stress-strain induced bainite transformation. The mid-ridge is the result of rapid nucleation and growth of the initial shear mechanism of bainite transformation. The existence of mid-level faults in mid-ridge provides a basis for the existence of shear mechanism in bainite transformation.