准下贝氏体的孪晶及形成机制

TWINS AND ITS FORMATION MECHANISM IN LOWER META-BAINITE

透射电镜实验证实在含硅钢准下贝氏体组织中存在挛晶亚结构，贝氏体中脊亦存在孪晶.中脊与残余奥氏体（Ar）李晶是贝氏体铁素体切变共格长大时协调均匀切变形成的形变孪晶贝氏体铁素体（BF）板条内孪晶主要是其横向侧面切变增厚时残余奥氏体的遗传李晶，且孪晶面与界面台阶有对应关系．

By TEM it has been confirmed that twin substructures exist in lower metabainite in silicon-containing steel. A large number of twins was found in bainitic midribs for first time. Twins in midribs (M-M) as well as retained austenite (Ar) are deformation twins formed by coordinating uniform shear deformation as bainitic ferrite lath grows, twins in bainitic ferrite (BF)mainly are those inherited in retained austenite as BF thickens by shear mechanism in broad face. and twin planes correspond to the interface ledges, which shows ledges can not migrate along side direction of broad face. Based on the results, a model of twin formation in lower meta-bainite was suggested.