Observation of Microstructure in Thick Steel with High Voltage TEM

Yamada, K.; Nakamichi, Haruo; Sato, Kaoru; Yasunaga, Kunio; Daio, Takeshi; Matsumura, Shinya

doi:10.2355/tetsutohagane.98.469

Cited by 10 publications

(5 citation statements)

References 9 publications

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“…However, it is also demonstrated that in these two samples an increase in the dislocation density becomes slow in the later stage of deformation, indicating that dynamic recovery occurs significantly [22]. Similar tendency in dislocation structure development has been observed in low carbon steels with nano-sized (Ti,Mo)C particles [22,42].…”

Section: Dislocation Structuressupporting

confidence: 57%

Stress–strain behavior of ferrite and bainite with nano-precipitation in low carbon steels

et al. 2015

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We systematically investigate stress-strain behavior of ferrite and bainite with nano-sized vanadium carbides in low carbon steels; the ferrite samples were obtained through austenite/ferrite transformation accompanied with interphase precipitation and the bainite samples were via austenite/bainite transformation with subsequent aging. The stress-strain curves of both samples share several common features, i.e. high yield stress, relatively low work hardening and sufficient tensile elongation. Strengthening contributions from solute atoms, grain boundaries, dislocations and precipitates are calculated based on the structural parameters, and the calculation result is compared with the experimentally-obtained yield stress. The contributions from solute atoms and grain boundaries are simply additive, whereas those from dislocations and precipitates should be treated by taking the square root of the sum of the squares of two values. Nano-sized carbides may act as sites for dislocation multiplication in the early stage of deformation, while they may enhance dislocation annihilation in the later stage of deformation. Such enhanced dynamic recovery might be the reason for a relatively large elongation in both ferrite and bainite samples.

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Section: Dislocation Structuressupporting

confidence: 57%

Stress–strain behavior of ferrite and bainite with nano-precipitation in low carbon steels

et al. 2015

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“…In the Ti-added sample transformed for 0.5 h having the average carbide diameter of 5.5 nm, a quite uniform dislocation structure is observed even after 1% of strain, and the dislocation density is already high. Yamada et al 47) observed the dislocation structure after 0.2% plastic strain of the steel with nanosized (Ti,Mo)C particles and found a high density of dislocations with a uniform distribution in the ferrite matrix, corresponding well with the resent observation. Tensile deformation of 5% strain leads to a higher density of dislocations in the Ti-added steel, but the dislocation distributions is quite uniform.…”

Section: Work Hardening Behavior and Ductilitymentioning

confidence: 52%

Tensile Behavior of Ti,Mo-added Low Carbon Steels with Interphase Precipitation

et al. 2014

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Tensile behavior and structure-property relationship of ferritic steels with nano-sized carbide dispersion were invesigated using Ti-added steel and Ti,Mo-added low carbon steels. By austenitizing followed by isothermal heat treatment at 700°C, polygonal ferrites containing very fine carbides of TiC and (Ti,Mo)C were obtained in the Ti-added and the Ti,Mo-added steels, respectively. The size of such carbides was finer in the Ti,Mo-added steel than in the Ti-added steel at the same isothermal holding. The results of tensile tests for these samples showed that the strength is higher as the carbide size is smaller. The structure-based strength calculation led to a good agreement with the experiments, when it was assumed that the Ashby-Orowan mechanism is dominant for precipitation strengthening of nano-sized alloy carbides. It was also suggested that a relatively large tensile ductility is related to enhanced recovery during the tensile deformation, accompanied with promotion of secondary slips or cross slips in a finer scale due to the nano-sized particles.

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“…17) Yamada et al confirmed the suppression of dislocation slip in Ti-and Mo-added steel by measuring the breaking angles and the particle distances using in-situ tensile testing in TEM. 18) In-situ tensile experiment is capable of observing the movements of dislocations and particles dynamically, so that the it is the method to elucidate the dispersion strengthening mechanisms.…”

Section: )mentioning

confidence: 99%

<i>In-situ</i> TEM Observation of the Interaction between Dislocations and Particles of Cu-added Ferritic Stainless Steel under High-temperature Straining

et al. 2016

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Cu is always present in the matrix when ferritic steels were prepared from ferrous scrap. When the ferritic steels are aged thermally, Cu particles start appearing and dispersing finely and homogeneously, which may result the steels strengthened by dispersion strengthening. In this study, the interactions between Cu particles and dislocations were examined via high-temperature in-situ TEM straining. Cu-added ferritic stainless steel (Fe-18.4%Cr-1.5%Cu) was used in the present study. Specimen was aged at 1 073 K for 360 ks. Microstructure of specimen was analyzed by JEM-3200FSK and high-temperature in-situ TEM straining was conducted using JEM-1300NEF. Progressing dislocations in matrix contacted with the Cu particle at right angle. This result implies that there is an attractive interaction between dislocations and the Cu particle. Furthermore, dislocations pass through the particle after contacting it, so that the interaction with dislocations and particles should be explained by Srolovitz mechanism.

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Observation of Microstructure in Thick Steel with High Voltage TEM

Cited by 10 publications

References 9 publications

Stress–strain behavior of ferrite and bainite with nano-precipitation in low carbon steels

Stress–strain behavior of ferrite and bainite with nano-precipitation in low carbon steels

Tensile Behavior of Ti,Mo-added Low Carbon Steels with Interphase Precipitation

<i>In-situ</i> TEM Observation of the Interaction between Dislocations and Particles of Cu-added Ferritic Stainless Steel under High-temperature Straining

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