显微带细化组织和两相组织对低Cr合金钢高温断裂行为的影响

针对低Cr合金钢进行轧制工艺设计，分别制备出显微带细化的1#组织和以马氏体/铁素体为特征的2#组织，在550℃、650℃、750℃对其进行高温拉伸实验。拉伸曲线和断后组织的分析结果表明，温度的升高和应变速率的减小能够促进再结晶过程，最终不但导致抗拉强度的降低，同时也减弱了组织内部滑移系统对亚结构界面运动的影响；然而具有2#两相组织的钢板其650℃的抗拉强度却比550℃的高。对组织和析出状态分析后认为，650℃变形时铁素体晶粒中大量形成的M₇C₃析出物显著提高了铁素体基体的强度，进而通过平衡其与回火马氏体之间的性能关系，使拉伸性能得以改善。

Influence of Microbands Refined Microstructure and Two Phase Microstructure on High Temperature Fracture Behaviors of a Low Cr Alloy Steel

Two kinds of microstructure, namely the microbands refined microstructure and the martensite-ferrite two phase microstructure, were obtained for a low Cr alloy steel by using different rolling technologies, then the fracture behavior of the steel under different tensile conditions was investigated. Analysis of the strain-stress curves and the microstructures after deformation show that the increase of rolling temperature and the decrease of strain rate could reduce the tensile strength, meanwhile, the enhancing recrystallization process can release the constraint of interior slip systems on the motion of subboundaries. Abnormal increase of tensile strength at 650℃ for the two phase microstructure can be attributed to the numerous precipitation of M₇C₃ in the ferritic matrix, which balances the mechanical properties between ferrite and annealed martensite, therefore improves the tensile strength at 650℃.