Microstructural characteristics and toughness of the simulated coarse grained heat affected zone of high strength low carbon bainitic steel

Lan, Liangyun; Qiu, Chunlin; Zhao, Dewen; Gao, Xiuhua; Du, Linxiu

doi:10.1016/j.msea.2011.09.017

Cited by 256 publications

(111 citation statements)

References 28 publications

Supporting

Mentioning

103

Contrasting

Unclassified

Order By: Relevance

“…It is well known that the fatigue limit of matrix obtained via uniaxial fatigue tests is well correlated with Vickers hardness [21]: It has been reported that high-angle grain boundary plays a significant role as an obstacle for the crack growth along slip planes [11,12]. As was shown in Fig.…”

Section: Mechanism Determining Torsional Fatigue Strengthmentioning

confidence: 88%

“…For martensitic and bainitic steels, several researchers have pointed out in the case of uni-axial loading that crack initiation site is dependent on the material type and microstructure. For example, prior austenitic grain boundary in martensitic steels [9,10], {110} slip planes or bainitic lath/block interface in bainitic steels [11] and martensite-austenite constituent [12] have been reported as crack initiation sites. However, it has not yet been clarified which microstructural feature dominates the shear-mode crack initiation in each case.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Shear-mode Crack Initiation Behavior in the Martensitic and Bainitic Microstructures

Wada

Yoshimura

Yamamoto³

et al. 2018

MATEC Web Conf.

View full text Add to dashboard Cite

Abstract. Fully reversed torsional fatigue tests were conducted to elucidate the behaviour of shear-mode crack initiation and propagation in one martensitic and two bainitic steels. The relationship between the crack initiation site and microstructure was investigated by means of an electron backscatter diffraction (EBSD) technique. From the S-N diagram, two notable results were obtained: (i) the shear-mode crack was initiated on the prior austenitic grain boundary in martensitic steel, while in bainitic steels, the crack was initiated along the {110} plane; one of the slip planes of bcc metals, and (ii) the torsional fatigue limit of lower bainitic steel with finer grains was 60 MPa higher than that of upper bainitic steel with coarser grains even though the hardnesses were nearly equivalent. The mechanism determining the torsional fatigue strength in these steels is discussed from the viewpoint of microstructure morphology.

show abstract

Section: Mechanism Determining Torsional Fatigue Strengthmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Shear-mode Crack Initiation Behavior in the Martensitic and Bainitic Microstructures

Wada

Yoshimura

Yamamoto³

et al. 2018

MATEC Web Conf.

View full text Add to dashboard Cite

show abstract

“…Grain boundary is well-known as the microstructure unit controlling the toughness of steels [14,30,31]. It owns high potential energy to impede crack propagation, and the increase of grain boundary density, namely the refinement of grain, can significantly improve the toughness of steels.…”

Section: Effect Of Grain Boundary On Impact Toughness In the Simulatementioning

confidence: 99%

The Role of the Bainitic Packet in Control of Impact Toughness in a Simulated CGHAZ of X90 Pipeline Steel

Guo

Fan

Wang

et al. 2016

Metals

View full text Add to dashboard Cite

X90 pipeline steel was processed with the simulated coarse grain heat affect zone (CGHAZ) thermal cycle with heat input varying from 30 kJ/cm to 60 kJ/cm, the microstructures were investigated by means of optical microscope (OM), scanning electron microscope (SEM), electron backscattering diffraction (EBSD), and transmission electron microscope (TEM), and the impact properties were evaluated from the welding thermal cycle treated samples. The results indicate that the microstructure is primarily composed of lath bainite. When decreasing the heat input, both bainite packet and block are significantly refined, and the toughness has an increased tendency due to the grain refinement. The fracture surfaces all present cleavage fracture for the samples with different heat inputs. Moreover, the average cleavage facet size for the CGHAZ is nearly equal to the average bainite packet size, and the bainitic packet boundary can strongly impede the crack propagation, indicating that the bainitic packet is the most effective unit in control of impact toughness in the simulated CGHAZ of X90 pipeline steel.

show abstract

“…However, a heat-affected zone (HAZ) mainly comprising so-called upper bainite is formed adjacent to the welded joint through the repetition of heating and cooling during the welding process. [1][2][3][4][5][6] In addition, untransformed austenite with a high carbon content is retained between the bainite laths through holding at an elevated temperature range in which upper bainite forms. The retained austenite is partly transformed to martensite by cooling or mechanical processing, which causes the so-called martensiteaustenite constituent.…”

Section: Introductionmentioning

confidence: 99%

Micro-tensile Behaviour of Low-alloy Steel with Bainite/martensite Microstructure

et al. 2016

View full text Add to dashboard Cite

Micro-tensile testing and numerical analysis using a crystal plasticity finite element method (CPFEM) were employed to elucidate the deformation behaviour of bainite/martensite structures of a low-alloy steel. The bainite single-phase specimens exhibited habit-plane-orientation-dependent yielding, similar to the martensite single-phase specimens. In the bainite/martensite dual-phase specimen, deformation concentrated in the bainite region oriented favourably for in-habit-plane slip, leading to low-ductility fracture. With consideration of the habit-plane-orientation-dependent yielding, the present CPFEM analysis successfully reproduced the anisotropic plastic deformation behaviour of the single-phase steels observed in the experiments. The numerical results for the bainite/martensite specimen showed slip localization in the bainite region and stress concentration near the interphase boundary. This suggests that the interphase boundary can be a site for the fracture origin.KEY WORDS: micromechanical characterisation; bainite; martensite-austenite constituent; crystal plasticity finite element analysis; plastic anisotropy; habit plane.tensitic phases hinders the understanding of the mechanical response of each phase.Mine et al. have analysed the mechanical characteristics of the microconstituents in the single-phase lath martensite structure of a low-alloy steel using micro-tensile testing.12) This study revealed that lath martensite structures with single packets exhibited moderate ductility and that the plastic deformation behaviour depended on the habitplane orientation relative to the loading direction. Thus, micro-tensile testing allows for the analysis of deformation behaviour on the microstructural scale. In addition, a microtensile test study by Ogata et al. indicated that pre-strained ferrite/martensite dual-phase steel was embrittled by ultra grain refinement in the ferrite region, rather than by cracking in the martensite region.13) This finding suggested that martensite was not always the main cause of embrittlement in high-strength steels. In the present study, microtensile testing was employed to characterise the mechanical response of each phase in a bainite/martensite structure. Additionally, numerical analysis with crystal plasticity finite element method (CPFEM) was performed to elucidate the microscopic mechanism of the experimentally observed deformation behaviour.The CPFEM analyses have helped in understanding plastic behaviours, 14,15) and studies on dual-phase steels successfully reproduced the observed deformation and fracture behaviours. 16,17) However, few studies have applied CPFEM to bainite/martensite dual-phase-structured steel. Therefore, in the present study, we confirm the applicability of a simple CPFEM with linear hardening laws to the deforma- ISIJ International, Vol. 56 (2016), No. 12tion behaviour of the bainite and martensite single-phase structures. Furthermore, by using the material parameters identified in the analyses of single-phase structures, the analysis of the bainit...

show abstract

Microstructural characteristics and toughness of the simulated coarse grained heat affected zone of high strength low carbon bainitic steel

Cited by 256 publications

References 28 publications

Shear-mode Crack Initiation Behavior in the Martensitic and Bainitic Microstructures

Shear-mode Crack Initiation Behavior in the Martensitic and Bainitic Microstructures

The Role of the Bainitic Packet in Control of Impact Toughness in a Simulated CGHAZ of X90 Pipeline Steel

Micro-tensile Behaviour of Low-alloy Steel with Bainite/martensite Microstructure

Contact Info

Product

Resources

About