Micro-tension behaviour of lath martensite structures of carbon steel

Mine, Yoji; Hirashita, Koichi; Takashima, Hiroki; Matsuda, Mitsuhiro; Takashima, Kazuki

doi:10.1016/j.msea.2012.09.099

Cited by 137 publications

(111 citation statements)

References 16 publications

(22 reference statements)

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“…[3] This implies an increase of high-angle boundaries in as-quenched martensite microstructure, which are effective barriers to dislocation movement during deformation of lath martensite and strongly affect the strengthening of the material. [3,[7][8][9] PAGS reduction has other consequences for the martensitic microstructure. It leads to a reduction of the Ms temperature [10,11] and may also cause an increase of the retained austenite (RA) fraction.…”

Section: Introductionmentioning

confidence: 99%

“…However, there is a lack of investigations that methodically study the effect of PAGS reduction by thermal cycling on the microstructure of lath martensite. Apart from the formermentioned implications of PAGS reduction, block orientations, which have an important role in mechanical response, [8] can be modified by thermal cycling and aligned in preferential directions. [6] The present work explores the process of thermal cycling as a method to reduce PAGS and analyze further formation of lath martensite upon quenching.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Prior Austenite Grain Size Refinement by Thermal Cycling on the Microstructural Features of As-Quenched Lath Martensite

Hidalgo

Santofimia

2016

Metall Mater Trans A

177

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Current trends in steels are focusing on refined martensitic microstructures to obtain high strength and toughness. An interesting manner to reduce the size of martensitic substructure is by reducing the size of the prior austenite grain (PAG). This work analyzes the effect of PAGS refinement by thermal cycling on different microstructural features of as-quenched lath martensite in a 0.3C-1.6Si-3.5Mn (wt pct) steel. The application of thermal cycling is found to lead to a refinement of the martensitic microstructures and to an increase of the density of high misorientation angle boundaries after quenching; these are commonly discussed to be key structural parameters affecting strength. Moreover, results show that as the PAGS is reduced, the volume fraction of retained austenite increases, carbides are refined and the concentration of carbon in solid solution as well as the dislocation density in martensite increase. All these microstructural modifications are related with the manner in which martensite forms from different prior austenite conditions, influenced by the PAGS.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of Prior Austenite Grain Size Refinement by Thermal Cycling on the Microstructural Features of As-Quenched Lath Martensite

Hidalgo

Santofimia

2016

Metall Mater Trans A

177

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“…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.…”

Section: Introductionmentioning

confidence: 84%

“…12) We prepared micro-tensile specimens with different habit plane orientations with respect to the loading direction (LD) to investigate the anisotropy in the plastic deformation behaviour of the bainitic single-phase microstructure, which has a lath structure similar to that of martensite. Figure 2 shows colour-coded maps of the gauge sections of tensile specimens based on EBSD analysis and the corresponding (110) pole figures.…”

Section: Micro-tensile Behaviour In Bainitementioning

confidence: 99%

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

et al. 2016

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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...

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“…Meanwhile, recent advances in the micro-mechanical testing techniques have helped elucidate the contribution of the micro-constituents to the mechanical properties in several steels and alloys. [9][10][11][12][13] Micro-tensile testing was employed in this study to clarify the deformation behavior at the interphase boundary in the inhomogeneous microstructures developed by cold rolling in the ferrite-martensite DP steel.…”

Section: Introductionmentioning

confidence: 99%

Quantification of Large Deformation with Punching in Dual Phase Steel and Change of its Microstructure –Part III: Micro-tensile Behavior of Pre-strained Dual-phase Steel

et al. 2016

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The deformation behavior of inhomogeneous microstructures developed by pre-straining was studied by micro-tensile testing to elucidate the cause of low hole expandability of ferrite-martensite dual-phase (DP) steels. Slip bands developed in the ferritic phase, when the DP steel was cold-rolled (CR) at a reduction of 60% in thickness; in the 88% CR microstructure, ultrafine ferrite grains with a strong texture were locally observed. While the nanohardness increased with increasing pre-strain in the ferritic phase, it was constant in the martensitic phase. Tensile tests using micrometer-sized specimens with ferritic and martensitic phases revealed that the ultrafine-grained ferritic microstructure exhibited high yield strength but low ductility when compared to the slip band ferritic microstructure. While a shear type fracture occurred without necking in the former, the latter exhibited a chisel-edge type failure. In the absence of ultra grain refinement by pre-straining, the inhibition of slip transfer by the interphase boundary was a major contributor to the strengthening in the DP steel. The ductility loss of the severely deformed DP steel was attributed to localized strain in the ultrafine-grained ferritic microstructure.

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Micro-tension behaviour of lath martensite structures of carbon steel

Cited by 137 publications

References 16 publications

Effect of Prior Austenite Grain Size Refinement by Thermal Cycling on the Microstructural Features of As-Quenched Lath Martensite

Effect of Prior Austenite Grain Size Refinement by Thermal Cycling on the Microstructural Features of As-Quenched Lath Martensite

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

Quantification of Large Deformation with Punching in Dual Phase Steel and Change of its Microstructure –Part III: Micro-tensile Behavior of Pre-strained Dual-phase Steel

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