【摘要】 本文研究了低碳合金钢奥氏体在连续冷却或等温转变过程中形成的组织形态和转变机理。结果表明在中温贝氏体区得到“粒状贝氏体”组织,在先共析转变区得到“粒状组织”。两者都有“铁素体基体+小岛”形貌。但前者有表面浮凸现象,铁素体呈长条状,与母相维持K-S关系,惯习面为{111}_γ,小岛也多星长条状平行排列。后者无表面浮凸,铁素体呈无规则形状,与母相无严格位向关系,小岛亦呈无规则排列。然而这两种组织都是由扩散型相变机制形成的。最后,提出了形成这两种组织的相变模型。更多还原

【Abstract】 Study was made of the microstructural morphology and phase transformation mechanism of the "ferrite+islands" formed either as granular bainite in upper region of temperature range of bainitic transformation or as so called "granular structure" in temperature range of pro-eutectoid transformation in the low carbon alloy steels. The granular bainite stands out in surface relief during its transformation Its ferrite grows up longitudinally and form parallel laths The K-S orientation relationship is kept between ferrite and austenite The morphology of its islands appears as the shape of short lath and with a tendency of being parallelly distributed in the bainite-ferrite matrix. The granular structure does not stand out in surface relief in the formation of equiaxial ferrite. It’s ferrite can grow across the grain boundary of parent phase, and has no strict orientation relationship with parent phase The shape of the islands is irregular, and its arrangement on the matrix is also irregular. The grain boundary of austenite couldn’t be revealed clearly Except the difference of the transformation temperature, the granular structure possessed Widmanstatten ferrite is similar to the granular bainite in characteristics. Finally, the models of the growth of granular bainite and granular structure are suggested.更多还原