Microstructure of reverted austenite in Fe-0.3N martensite

Sato, Mitsutaka; Matsumoto, Sou; Miyamoto, Gorō

doi:10.1016/j.scriptamat.2018.07.020

Cited by 14 publications

(3 citation statements)

References 15 publications

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“…This result is owing to the recovery of dislocation, rotation of crystal orientation, and migration of large angle boundaries by long‐time holding at a relatively high temperature. [ 46 ] Therefore, the dislocation density showed an increasing trend followed by a decreasing trend, as shown in Figure 9.…”

Section: Discussionmentioning

confidence: 94%

Effect of Heat Input on Austenite Reversion, Recrystallization, and Ensuing Impact Toughness in Simulated Intercritical Coarse‐Grained Heat Affected Zone of Medium Mn Steel

Tao,

Yao,

et al. 2024

steel research int.

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A systematic experimental study has been conducted on the simulated intercritical coarse‐grained heat affected zone of 690 MPa grade heavy‐plate medium Mn steel by tailoring heat input of the first welding pass to obtain the influence of initial microstructure on the austenite reversion mechanism, recrystallization, and resultant impact toughness. Results reveal that prior austenite grain size significantly increases from 30 ± 11, 41 ± 14 to 54 ± 15 μm with the increasing heat input from 15, 30 to 50 kJ cm−1, which affect the nucleation site of reversed austenite, recrystallization mechanism, and final microstructure. Accordingly, impact toughness is better at the heat input of 30 kJ cm−1 (75.2 ± 0.8 J) in comparison with that of 15 kJ cm−1 (63.3 ± 13.3 J) and 50 kJ cm−1 (26.7 ± 6.5 J) at −40 °C, which is mainly ascribed to the formation of lamellar heterogeneous structures, multiplication of slip system and morphology of high‐angle grain boundaries.

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Section: Discussionmentioning

confidence: 94%

Effect of Heat Input on Austenite Reversion, Recrystallization, and Ensuing Impact Toughness in Simulated Intercritical Coarse‐Grained Heat Affected Zone of Medium Mn Steel

Tao,

Yao,

et al. 2024

steel research int.

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“…Figure 9h is the (100) pole figure that combined the martensite and reverted austenite, in which red color represents the pole point of the reverted austenite and the pole point of martensite was marked with black color. The reflexes of reverted austenite inside circles of martensite are a characteristic of (100) pole figures showing the K-S orientation relationship [46,47]. It implies that the reversed austenite had the same orientation with the surrounding martensite variants.…”

Section: Discussionmentioning

confidence: 99%

Temperature Dependent Phase Transformation Kinetics of Reverted Austenite during Tempering in 13Cr Supermartensitic Stainless Steel

Zhang

Yin

et al. 2019

Metals

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The formation and growth kinetics of the reverted austenite during tempering in 13Cr supermartensitic stainless steel were investigated by a combination X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) in a scanning electron microscope (SEM). The reverted austenite precipitated at the martensite blocks, sub-blocks, laths and grain boundaries. The growth kinetics was established by Johnson-Mehl-Avrami (JAM) kinetics equation according to the volume fraction of the equilibrium reverted austenite at room temperature. The Avrami exponent value is 0.5, and the activation energy was estimated to be 369 kJ/mol, the kinetic model indicates that the mechanism of reverted austenite is diffusion-controlled and the growth of reverted austenite closely relies on the diffusion of the nickel (Ni) element. The experimental measured orientations of the reverted austenite are in good agreement with the theoretical ones, implying that the reverted austenite has the same orientation with the surrounding martensite, which meets the Kurdjumov–Sachs (K-S) orientation relationship. The orientation relationships minimize the strain energy of the phase transformation by reducing the crystallographic mismatch between phases.

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“…Therefore, it may be possible to obtain more retained  than Fe-C alloys under the same heat treatment conditions. We have systematically investigated the phase transformation behavior of Fe-N alloys prepared by gas nitriding technique, and found that in the reverse transformation of Fe-0.3N (mass%) martensite, globular  is nucleated from the prior  grain boundary and needle-shaped  from the lath/block boundary of martensite by simple annealing in + two-phase region, and that approximately 10% of retained  can be obtained 5) . Besides, in the ferrite transformation of Fe-0.3N austenite, the ferrite morphology changes from allotriomorph ferrite (AF) to Widmannstetten ferrite (WF) to BF as the holding temperature decreases, and a maximum retained  of 9% can be obtained at 600°C holding 6) .…”

Section: Introductionmentioning

confidence: 99%

Effects of Alloying Element on Bainitic Transformation in Fe-0.3N Alloy

Sato,

Shimaya,

Hara

et al. 2024

ISIJ Int.

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The effects of alloying elements on the bainite transformation behaviors were investigated for Fe-0.3N and Fe-0.3N-1M (M: Si, Cr, Mn, Mo) (mass%) alloys. Nitrogen (N) was introduced into austenite by gas nitriding and subsequent isothermal holding were employed at 500°C. Bainitic ferrite starts to form from the austenite grain boundaries in all alloys. Bainite structure changed from nitride-free bainite (B-Ⅰ type) to bainite accompanying film-like nitride precipitation between bainitic ferrite (B-Ⅱ type) with increasing holding time in Fe-0.3N alloy.The transformation kinetics was retarded by addition of all the alloying elements investigated, resulting in larger retained austenite fraction after subsequent cooling to room temperature. The retardation was significant with Cr and Mn addition.Quantitative evaluation of energy dissipation calculated from the interfacial N concentration showed that the effect of additive elements was small at short holding times. In this region, the dissipation due to the interfacial friction and the transformation strain were dominant. Whereas the effect of alloying elements appeared as the interface velocity decreased with increasing holding time.

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Microstructure of reverted austenite in Fe-0.3N martensite

Cited by 14 publications

References 15 publications

Effect of Heat Input on Austenite Reversion, Recrystallization, and Ensuing Impact Toughness in Simulated Intercritical Coarse‐Grained Heat Affected Zone of Medium Mn Steel

Effect of Heat Input on Austenite Reversion, Recrystallization, and Ensuing Impact Toughness in Simulated Intercritical Coarse‐Grained Heat Affected Zone of Medium Mn Steel

Temperature Dependent Phase Transformation Kinetics of Reverted Austenite during Tempering in 13Cr Supermartensitic Stainless Steel

Effects of Alloying Element on Bainitic Transformation in Fe-0.3N Alloy

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