Qiao Gui-Ying, Zhao Zhong-Tao, Shi Xian-Bo, Shan Yi-Yin, Gu Yu, Xiao Fu-Ren
Key Lab of Applied Chemistry of Hebei Province, School of Environment and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China.
Key Lab of Metastable Materials Science&Technology, Hebei Key Lab for Optimizing Metal Product Technology and Performance, College of Materials Science Engineering, Yanshan University, Qinhuangdao 066004, China.
Materials (Basel). 2021 Sep 16;14(18):5352. doi: 10.3390/ma14185352.
The strength and plasticity balance of F/B dual-phase X80 pipeline steels strongly depends on deformation compatibility between the soft phase of ferrite and the hard phase of bainite; thus, the tensile strength of ferrite and bainite, as non-negligible factors affecting the deformation compatibility, should be considered first. In this purely theoretical paper, an abstract representative volume elements (RVE) model was developed, based on the mesostructure of an F/B dual-phase X80 pipeline steel. The effect of the yield strength difference between bainite and ferrite on tensile properties and the strain hardening behaviors of the mesostructure was studied. The results show that deformation first occurs in ferrite, and strain and stress localize in ferrite prior to bainite. In the modified Crussard-Jaoul (C-J) analysis, as the yield strength ratio of bainite to ferrite (σy,B/σy,F) increases, the transition strain associated with the deformation transformation from ferrite soft phase deformation to uniform deformation of ferrite and bainite increases. Meanwhile, as the uncoordinated deformation of ferrite and bainite is enhanced, the strain localization factor (SLF) increases, especially the local strain concentration. Consequently, the yield, tensile strength, and yield ratio (yield strength/tensile strength) increase with the increase in σy,B/σy,F. Inversely, the strain hardening exponent and uniform elongation decrease.
F/B双相X80管线钢的强度与塑性平衡很大程度上取决于铁素体软相和贝氏体硬相之间的变形协调性；因此，作为影响变形协调性的不可忽视的因素，铁素体和贝氏体的抗拉强度应首先予以考虑。在这篇纯理论论文中，基于F/B双相X80管线钢的细观结构建立了一个抽象的代表性体积单元（RVE）模型。研究了贝氏体与铁素体屈服强度差对细观结构拉伸性能和应变硬化行为的影响。结果表明，变形首先发生在铁素体中，且在贝氏体之前应变和应力集中于铁素体。在修正的Crussard-Jaoul（C-J）分析中，随着贝氏体与铁素体的屈服强度比（σy,B/σy,F）增加，与从铁素体软相变形到铁素体和贝氏体均匀变形的变形转变相关的转变应变增加。同时，随着铁素体和贝氏体不协调变形的增强，应变局部化因子（SLF）增加，尤其是局部应变集中。因此，屈服强度、抗拉强度和屈标比（屈服强度/抗拉强度）随σy,B/σy,F的增加而增加。相反，应变硬化指数和均匀伸长率降低。
