铁素体/贝氏体双相钢的变形和断裂特性

对一种低碳硅锰钢进行TMCP实验,获得了不同铁素体形态的铁素体/贝氏体双相钢(FB钢),研究了FB钢在单轴拉伸下的变形行为及断裂特性,结果表明:在均匀塑性变形阶段,FB钢的瞬时加工硬化指数n*值与真应变ε的关系曲线可分为n*值较高、n*值随ε缓慢下降以及n*值随ε迅速下降三个阶段,与等轴铁素体/贝氏体双相钢相比,准多边形铁素体/贝氏体双相钢的强度和低应变区的n*值均比较高,FB钢拉伸试样颈缩区的孔洞或微裂纹产生在F-B相界面附近和铁素体内,有助于减弱裂纹尖端附近的局部应力集中,改善钢材的抗裂纹扩展性能.

Deformation and fracture characteristics of ferrite/bainite dual-phase steels

The deformation and fracture characteristics of a low carbon Si–Mn steel with ferrite/bainite dual–phase structure were investigated by thermo–mechanical controlled process (TMCP). The results showed that the curves of the instantaneous work–hardening factor n* value versus true strain ε are made up with three stages during uniform plastic deformation: n* value is relatively higher at stage I, decreases slowly with  ε  in stage  II, and then decreases quickly with ε in stage III. Compared tothe equiaxed ferrite/bainite dual–phase steel, the quasi–polygonal ferrite/bainite dual–phase steel shows higher tensile strength and n*value in the low strain region. The voids or micro–cracks formed not only at ferrite–bainite interfaces but also within ferrite grains in the necked region, which can improve the property of resistance to crack propagation by reducing local stress concentration of the crack tips.