Non-equilibrium state and recovery of grain boundary structure. II. Energetic Analysis

Valiev, Ruslan Z.; Gertsman, V.Y.; Kaĭbyshev, O. A.

doi:10.1002/pssa.2210780121

Cited by 52 publications

(9 citation statements)

References 20 publications

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“…It is well recognized by the researchers in SPD community that grain boundaries are mostly deformation-induced grain boundaries at non-equilibrium state. Unique properties of UFG materials endowed by SPD such as mechanical properties [23], low-temperature superplasticity [24], ultra-fast diffusion [25], corrosion properties [26] has frequently been attributed to this high-density of non-equilibrium grain boundaries. Macroscopic appearances of corroded specimens after immersion tests in 0.6 mol/L NaCl solution for 4, 144, 192, 217 and 363 h are shown Figure 2.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Corrosion Resistance of Ultrafine-Grained Fe-Cr Alloys with Subcritical Cr Contents for Passivity

Rifai

Yuasa

Miyamoto

2018

Metals

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This work presents an experimental validation that an ultrafine grained (UFG) structure of binary Fe-Cr alloys fabricated by severe plastic deformation (SPD) can bring about dramatic improvements in the corrosion resistance. More specifically, UFG Fe-Cr alloys with subcritical chromium content for passivation (8% and 10% Cr) was found to exhibit passivity, and was resistant to corrosion in an aqueous 0.6 mol/L NaCl solution whereas coarse-grained Fe-12% Cr, which are known as a stainless steel and passive in most dilute aerated solution, was degraded by corrosion. The findings indicated that the critical threshold of Cr content required for establishing a protective layer by self-passivation in binary Fe-Cr alloy is microstructure dependent, and can be reduced by grain size reduction to a sub-micron scale by SPD.

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Section: Resultsmentioning

confidence: 99%

Enhanced Corrosion Resistance of Ultrafine-Grained Fe-Cr Alloys with Subcritical Cr Contents for Passivity

Rifai

Yuasa

Miyamoto

2018

Metals

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“…These GB dislocations are dissipated and rearranged by climbing assisted by thermal activation, recovering the equilibrium GB structure. 16) These reaction processes between lattice dislocations and GBs were directly observed by a transmission electron microscope.…”

Section: Random σ3mentioning

confidence: 99%

Effect of Grain Boundary Structure on Misorientation Change of Pure Copper Bicrystals Pressed by One-Pass Equal-Channel Angular Pressing

et al. 2013

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reports on the dynamic misorientation change absorbed by the grain boundaries themselves during one-pass equal-channel angular pressing (ECAP), the effect of grain boundary structure on the misorientation change during ECAP was examined as the next step. Two bicrystals with a 3{111} grain boundary and a random one were subjected to ECAP for one pass, and compared. Both the bicrystals were designed to have a similar slip pattern where slip activity was concentrated on one slip plane. Direct evidence of misorientation changes absorbed by grain boundary themselves was obtained again, and its marked dependency on grain boundary structure became evident. Namely, in 3 grain boundary, misorientation was partially carried by the grain interior in its vicinity, which stems from the dislocation accumulation. On the other hand, in the random grain boundary, most of the misorientation was carried by the boundary itself. These differences are discussed in terms of the capability as a sink of lattice dislocations during severe plastic deformation.

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“…The latter remark avoids considering the Valiev et al (1983) model which ignores the IGBD contribution to accommodation. After lattice dislocations have entered the GBs, these networks are perturbed and complete periodic reorganization must imply elastic interactions between extrinsic and intrinsic dislocations.…”

Section: Majormentioning

confidence: 99%

“…The absorption phenomena, decomposition or contrast spreading, have been largely investigated by transmission electron microscopy (TEM); several references have been given in recent papers (Priester 1997. There are two fundamental types of EGBD accommodation model: EGBD core delocalization which accounts for EGBD relaxation in a GB without a discrete intrinsic structure (Lojkowski et al 1977, Lojkowski andGrabski 1981) and EGBD decomposition followed by incorporation within the intrinsic network (Valiev et al 1983, Nazarov et al 1990. There are two fundamental types of EGBD accommodation model: EGBD core delocalization which accounts for EGBD relaxation in a GB without a discrete intrinsic structure (Lojkowski et al 1977, Lojkowski andGrabski 1981) and EGBD decomposition followed by incorporation within the intrinsic network (Valiev et al 1983, Nazarov et al 1990.…”

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confidence: 99%

In-situ transmission electron microscopy study of the dislocation accommodation in [101] tilt grain boundaries in nickel bicrystals

Poulat¹

1999

Philosophical Magazine A

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The relaxation of stresses associated to extrinsic grain-boundary dislocations (EGBDs) in singular Sˆ3, {111}, in vicinal Sˆ11, {311} and in general Sˆ11, {332} grain boundaries (GBs) has been investigated by in-situ transmission electron microscopy (TEM) using weak-beam conditions. In a singular Sˆ3, {111} GB, reactions of combination and annihilation occur between extrinsic and intrinsic dislocations when they initially intersect each other. These reactions yield the parallelism of the two types of dislocation which is the preliminary con® guration for any of the existing incorporation models to operate, but further evolution by decomposition of the EGBDs in glissile and sessile components, which can move away, as depicted by theory, was observed once only at a very high temperature. Furthermore, the rearrangement of all the sessile dislocations, extrinsic and intrinsic, in a periodic network was not observed, even after maintaining the thin foil at 9308Cˆ0:6T m (T m is the melting temperature) for a long time. In vicinal Sˆ11, {311} GBs, the continuous spreading of EGBD contrasts, previously observed by TEM in bright-® eld conditions, has been proved to be a decomposition process. Indeed, owing to the weak-beam technique, the wide image of a relaxed EGBD has been resolved in a set of small segments resulting from the interaction between the EGBD and the intrinsic dislocations. After annealing the thin foil at temperatures up to 0.4T m , all the GBDs had rearranged themselves in a quasiperiodic network, indicating that equilibration is almost achieved. In general Sˆ11, {332} GBs, the widening of the EGBD contrasts has never been associated with a decomposition phenomenon. No discrete product of EGBD decomposition has ever been observed by TEM, even in weak-beam conditions. The di erences between the accommodation processes according to the GB type are discussed by referring to the GB atomic structure as described by the structural unit model.

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Non-equilibrium state and recovery of grain boundary structure. II. Energetic Analysis

Cited by 52 publications

References 20 publications

Enhanced Corrosion Resistance of Ultrafine-Grained Fe-Cr Alloys with Subcritical Cr Contents for Passivity

Enhanced Corrosion Resistance of Ultrafine-Grained Fe-Cr Alloys with Subcritical Cr Contents for Passivity

Effect of Grain Boundary Structure on Misorientation Change of Pure Copper Bicrystals Pressed by One-Pass Equal-Channel Angular Pressing

In-situ transmission electron microscopy study of the dislocation accommodation in [101] tilt grain boundaries in nickel bicrystals

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