Transition of Deformation Mechanism with Grain Refinement in Interstitial-Free Steel

Itoh, S.; Nakazawa, Kasane; Matsunaga, Takuya; Matsukawa, Y.; Satoh, Yuhki; Abe, Hiroaki

doi:10.2355/isijinternational.54.1729

Cited by 10 publications

(4 citation statements)

References 33 publications

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“…On the other hand, in alloys with a bcc structure, such as the IF steel in this study, the screw dislocation, which has lower mobility than the edge dislocation, is dominant for slip deformation, and the slip plane is not always clearly restricted due to the frequent occurrence of cross slip. Regarding dislocation-grain boundary interaction, a phenomenon in which dislocations sink to the grain boundary has been pointed out in a bcc metal, 30) and a similar phenomenon was actually observed in in-situ deformation in a TEM. 31) Although the details of the mechanism of dislocation-grain boundary interaction are unclear, this phenomenon may be related to the high frequency of cross slip.…”

Section: Grain D Grainsupporting

confidence: 59%

Effects of Grain Boundary Geometry and Boron Addition on the Local Mechanical Behavior of Interstitial-Free (IF) Steels

Endoh¹,

Kimura

et al. 2021

Mater. Trans.

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Nanoindentation measurements on various grain boundaries were performed to clarify the effects of the geometry of neighboring grains and the addition of boron (B) on plasticity resistance in the vicinity of grain boundaries in interstitial free (IF) steels. We define a parameter, ¡, which is measured by the slope of a P/hh curve with load, P, and displacement, h, to estimate the resistance against plastic deformation in the grain interior and at the grain boundaries. The value of ¡ is almost constant with the geometric compatibility factor of the grain boundaries. This result shows that the geometry of the neighboring grains does not affect the plasticity resistance of the grain boundaries. However, the value of ¡ increases by the addition of B due to the segregation of B and Ti to the grain boundaries. It is indicated that the elemental segregation to the grain boundaries enhances the resistance to the plastic deformation in the vicinity of the grain boundaries.

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Section: Grain D Grainsupporting

confidence: 59%

Effects of Grain Boundary Geometry and Boron Addition on the Local Mechanical Behavior of Interstitial-Free (IF) Steels

Endoh¹,

Kimura

et al. 2021

Mater. Trans.

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“…This indicates that interaction between dislocations became stronger, because this type of gradation has been previously reported: the KAM map corresponds well with the formation of a cell structure. 14) TEM observations were performed to confirm the dislocation structures in the first and the second steady states. Bright-field images recorded for the two states are shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Double Steady-State Creep Behavior in Solid-Solute-Strengthened Zircaloy-4

et al. 2022

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Long-term creep tests on the solid-solute-strengthened zirconium alloy, i.e., Zircaloy-4, revealed the presence of double steady-state creep behavior at 623673 K. The first steady state manifested as a faster creep strain rate at a strain (¾) of ³0.05, and the second appeared with a slower creep strain rate at ¾ > 0.1. Several electron microscopy revealed a change in the dislocation structure during creep from the motion of individual dislocations to the generation of cell structure. Along with this change, the stress exponent differed in each steady state, increasing from 6.7 in the first steady state to 10 in the second steady state. The temperature dependency also changed because the apparent activation energies were 201 and 298 kJ/mol for the first and second steady states, respectively. These results show that pipe diffusion and self-diffusion are the rate-controlling processes in the first and second steady state, respectively. Because such changes in the deformation mechanism during one creep curve are highly unusual, the double steady state is a characteristic feature of high-temperature deformation in Zircaloy-4. For engineering, observation of the second steady state is necessary in estimating the time-to-rupture by means of the MonkmanGrant relationship because creep strain rates at the first steady state deviate from the relationship.

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“…As shown in Figs. From a report that grain boundary sliding is activated by absorption of dislocations at grain boundaries, 35) therefore, the fracture mechanism of uncharged ultrafine-grained iron can be schematically illustrated in Fig. 14(a).…”

Section: Fracture Mechanism Of Uncharged Specimensmentioning

confidence: 99%

Hydrogen Embrittlement Mechanism of Ultrafine-grained Iron with Different Grain Sizes

2023

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To investigate the effect of grain sizes on hydrogen embrittlement of 4N-purity iron, miniature tensile tests were conducted after hydrogen charging for the ultrafine-grained specimens produced by highpressure torsion and subsequent annealing. Hydrogen embrittlement indexes defined from reduction of area were increased with decreasing grain size, and shear-type fracture occurred with fine dimples on the fracture surface of the diagonally raptured tensile specimen with a smaller grain size. The formation and growth of microvoids at triple junctions of grain boundaries ahead of propagated cracks were responsible for such earlier shear-type fracture because necking between adjacent microvoids more likely and extensively occurred. In the specimens with larger grain sizes or without hydrogen charging, on the other hand, local coalescence and growth of microvoids were predominant due to longer distances between triple junctions, resulting in void coalescence-type fracture with coarser dimple patterns. Therefore, hydrogen atoms introduced by hydrogen charging are considered to enhance the formation of deformation-induced vacancies in ultrafine-grained iron, resulting in shear-type fracture with finer dimple patterns.

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Transition of Deformation Mechanism with Grain Refinement in Interstitial-Free Steel

Cited by 10 publications

References 33 publications

Effects of Grain Boundary Geometry and Boron Addition on the Local Mechanical Behavior of Interstitial-Free (IF) Steels

Effects of Grain Boundary Geometry and Boron Addition on the Local Mechanical Behavior of Interstitial-Free (IF) Steels

Double Steady-State Creep Behavior in Solid-Solute-Strengthened Zircaloy-4

Hydrogen Embrittlement Mechanism of Ultrafine-grained Iron with Different Grain Sizes

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