铁素体/贝氏体(F/B)双相钢组织调控及其抗变形行为分析

CONTROL OF MICROSTRUCTURES OF FERRITE/BAINITE(F/B) DUAL-PHASE STEELS AND ANALYSIS OF THEIR RESISTANCE TO DEFORMATION BEHAVIOR

本文针对低C,高Mn和高Nb化学成分,采用轧后弛豫控制相变的组织调控技术得到5种不同铁素体/贝氏体(F/B)体积含量的双相组织钢.用改进的C-J分析方法分析了软相(铁素体)含量,研究了晶粒尺寸对加工硬化性能的影响,以及以铁素体和贝氏体为主的软硬相混合组织的塑性变形协调关系.并用电子背散射(EBSD)技术验证了双相组织在均匀塑性变形阶段的协调变形行为.结果表明,软硬相的合理比例有利于提高加工硬化程度(高Rt_(1.5)/Rt_(0.5)),降低屈强比,同时能保证较高的均匀变形能力.铁素体与贝氏体之间的协调变形是提高双相组织钢应力比和均匀伸长率的主要机制.

Five ferrite/bainite（F/B） dual-phase steels with the chemistry of low carbon,high manganese and high niobium,and different volume fractions of bainite（15%—98%） were produced by control rolling＋relaxing＋ACC processing.With the help of the modified Crussard-Jaoul（C-J） analysis,the effects of soft phase（ferrite） content and its grain size on the work-hardening behavior of the steels and the cooperative deformation relationship between softer phase and harder phase were studied,which was validated by EBSD analysis.The results illustrate that a reasonable proportion of F/B can be helpful to improve initial work-hardening（a high R_（t1.5）/R_（t0.5））,reduce the yield ratio, and maintain a high uniform elongation.It is known that the cooperative deformation of ferrite and bainite is the main mechanism for improving the stress ratio and the uniform elongation of the F/B dual-phase steels.