Strain Measurement of Micrometre-Sized Structures under Tensile Loading by Using Scanning White-Light Interferometry

Ito, Takashi; Mine, Yoji; Otsu, Masaaki; Takashima, Kazuki

doi:10.2320/matertrans.mg201616

Cited by 7 publications

(2 citation statements)

References 18 publications

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“…Tensile tests were performed at room temperature under laboratory atmospheric conditions with a displacement rate of 0.1 μm s –1 , corresponding to a strain rate of 2 × 10 –3 s –1 . The set-up has been described in more detail in a previous study 30 . The gauge section of the tensile specimen was monitored during tensile testing using an optical microscope to dynamically measure the strain as a function of time.…”

Section: Methodsmentioning

confidence: 99%

Excellent mechanical properties of taenite in meteoric iron

Ueki

Mine

Takashima

2021

Sci Rep

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Meteoric iron is the metal that humans first obtained and used in the earliest stage of metal culture. Advances in metallographic analysis techniques have revealed that meteoric iron largely comprises kamacite, taenite, and cohenite, which correspond to ferrite, austenite, and cementite in artificial steel, respectively. Although the mechanical properties of meteoric irons were measured previously to understand their origin and history, the genuine mechanical properties of meteoric iron remain unknown because of its complex microstructure and the pre-existing cracks in cohenite. Using micro-tensile tests to analyse the single-crystalline constituents of the Canyon Diablo meteorite, herein, we show that the taenite matrix exhibits excellent balance between yield strength and ductility superior to that of the kamacite matrix. We found that taenite is rich in nitrogen despite containing a large amount of nickel, which decreases the nitrogen solubility, suggesting that solid-solution strengthening via nitrogen is highly effective for the Fe–Ni system. Our findings not only provide insights for developing advanced high-strength steel but also help understand the mysterious relationship between nitrogen and nickel contents in steel. Like ancient peoples believed that meteoric iron was a gift from the heavens, the findings herein imply that this thought continues even now.

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Section: Methodsmentioning

confidence: 99%

Excellent mechanical properties of taenite in meteoric iron

Ueki

Mine

Takashima

2021

Sci Rep

Self Cite

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“…The gauge section of each specimen was monitored using an optical microscope during tensile testing. The strain measurement 18) was performed using images obtained continuously during tensile testing.…”

Section: Methodsmentioning

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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