20Mn钢复相组织变形和断裂过程的研究

本文利用透射电子显微分析技术对20Mn钢复相组织的变形和断裂规律进行了原位观察,研究变形过程中组织结构对强化过程的影响,特别是形变强化指数、变形量和组织三者之间的关系;同时对试验钢的断裂机制进行了分析,即观察扩展裂纹前沿位错组态的变化及裂纹的动态扩展过程。

THE TRANSMISSION ELECTRON MICROSCOPY ANALYSIS OF THE PLASTIC DEFORMATION AND FRACTURE BEHAVIOR FOR 20Mn DUAL PHASE STEEL

The plastic deformation and the fracture behavior of 20Mn dual phasesteel are in-situ investigated by transmission electron microscopy. The rela-tionship among strengthening exponential, plastic deformation range andelectro-microstructure is particularly examined. The fracture mechanism of thedual phase structure is also analysed. Some conclusions are drawn from theexperiment: (1) the dislocation array in the ferrites varies with the differentdeformation degrees of the steel; (2) as soon as cells are formed in ferrite thestrengthening exponential value n will tend to decrease; (3) the crack tip is adislocation source which can emit dislocation lines; (4) if the hard phaseis martensite, dual phase structure is of fairly good ductility and toughness;whereas if the hard phase is bainite, its ductility and toughness become worse;(5) dislocation lines will escape from the foil surface through the cross slip.