A series of ferrite/bainite(F/B) multi-phase steels containing different volume fractions of ferrite were obtained.The effect of soft phase(ferrite) content on the work-hardening behavior of the steel was studied by t...A series of ferrite/bainite(F/B) multi-phase steels containing different volume fractions of ferrite were obtained.The effect of soft phase(ferrite) content on the work-hardening behavior of the steel was studied by the finite element simulation with V-BCC model and the modified Crussard-Jaoul(C-J) analysis.It is shown that the multi-phase steels have an excellent anti-deformation ability,such as higher stress ratio(R t1.5 /R t0.5),higher uniform elongation and lower yield to tensile strength ratio.For the F/B multi-phase steels,increasing the proportion of ferrite would help to increase the uniform elongation.However,introducing much more fraction of ferrite would not be helpful to improve the stress ratio of multi-phase steel.The ferrite plastic strain constrained by bainite would be beneficial to increasing the work hardening rate.The optimum proportion of ferrite will result both higher stress ratio and uniform elongation in multi-phase steel.展开更多
The purpose of this study was to describe the roles of microstructure types and grain boundary characteristics in fatigue crack propagation behavior in ferrite-pearlite steel and ferrite-bainite steel.The ferrite-bain...The purpose of this study was to describe the roles of microstructure types and grain boundary characteristics in fatigue crack propagation behavior in ferrite-pearlite steel and ferrite-bainite steel.The ferrite-bainite dual-phase steel was obtained by intermediate heat treatment conducted on ferrite-pearlite low carbon steel.This paper presents the results from investigation using constant stress-controlled fatigue tests with in-situ scanning electron microscopy(SEM),electron backscattering diffraction(EBSD) and fatigue fractography analysis.Microscopic images arrested by in-situ SEM showed that the second hard bainite phase distributed in the soft ferrite matrix had a significant effect on preventing the cracks opening compared with pearlite,and that the cracks in ferrite-bainite steel were "locked" in the second hard bainite phase while the crack propagation path in ferrite-pearlite steel was more tortuous.Moreover,the fatigue fracture surface analysis and the coincidence site lattice(CSL) obtained by EBSD indicated that low-CSL grain boundaries in ferrite-bainite steel distributed more uniformly,which has a more significant effect on the resistance of crack propagation.It was revealed that ferrite-bainite dual-phase microstructures could inhibit the fatigue crack propagation more effectively than ferrite-pearlite microstructures.展开更多
基金supported by the National Basic Research Program of China ("973" Program) (Grant No. 2010CB630801)
文摘A series of ferrite/bainite(F/B) multi-phase steels containing different volume fractions of ferrite were obtained.The effect of soft phase(ferrite) content on the work-hardening behavior of the steel was studied by the finite element simulation with V-BCC model and the modified Crussard-Jaoul(C-J) analysis.It is shown that the multi-phase steels have an excellent anti-deformation ability,such as higher stress ratio(R t1.5 /R t0.5),higher uniform elongation and lower yield to tensile strength ratio.For the F/B multi-phase steels,increasing the proportion of ferrite would help to increase the uniform elongation.However,introducing much more fraction of ferrite would not be helpful to improve the stress ratio of multi-phase steel.The ferrite plastic strain constrained by bainite would be beneficial to increasing the work hardening rate.The optimum proportion of ferrite will result both higher stress ratio and uniform elongation in multi-phase steel.
文摘The purpose of this study was to describe the roles of microstructure types and grain boundary characteristics in fatigue crack propagation behavior in ferrite-pearlite steel and ferrite-bainite steel.The ferrite-bainite dual-phase steel was obtained by intermediate heat treatment conducted on ferrite-pearlite low carbon steel.This paper presents the results from investigation using constant stress-controlled fatigue tests with in-situ scanning electron microscopy(SEM),electron backscattering diffraction(EBSD) and fatigue fractography analysis.Microscopic images arrested by in-situ SEM showed that the second hard bainite phase distributed in the soft ferrite matrix had a significant effect on preventing the cracks opening compared with pearlite,and that the cracks in ferrite-bainite steel were "locked" in the second hard bainite phase while the crack propagation path in ferrite-pearlite steel was more tortuous.Moreover,the fatigue fracture surface analysis and the coincidence site lattice(CSL) obtained by EBSD indicated that low-CSL grain boundaries in ferrite-bainite steel distributed more uniformly,which has a more significant effect on the resistance of crack propagation.It was revealed that ferrite-bainite dual-phase microstructures could inhibit the fatigue crack propagation more effectively than ferrite-pearlite microstructures.
