Internal-friction analysis of dislocation–interstitial carbon interactions in press-hardened 22MnB5 steel

Choi, Won Seok; Lee, Jewoong; Cooman, Bruno C. De

doi:10.1016/j.msea.2015.05.055

Cited by 30 publications

(25 citation statements)

References 25 publications

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“…Results from 4340 steels [3,4] are, in many ways, similar to data collected from other alloys with martensitic microstructures [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Oftentimes, transition-iron-carbide precipitates appear to exhibit a rodlike or needlelike morphology [2,6,7,10,12,15,16,18], but upon closer examination at high magnification, numerous transmission electron microscope (TEM) images have revealed that the ''rods'' were composed of individual, closely spaced, equiaxed precipitates of very small size (e.g., less than 10 nm) [2, 8-12, 15, 16, 18]. These nearly equiaxed precipitates oftentimes were aligned along \100[ directions in martensite crystals [2-6, 12, 17-19].…”

Section: Introductionsupporting

confidence: 56%

“…Analysis of crystallographic aspects of the precipitates showed that the data could be interpreted as from a hexagonal epsilon-carbide phase or an orthorhombic eta-carbide phase [1,2]. Results from 4340 steels [3,4] are, in many ways, similar to data collected from other alloys with martensitic microstructures [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Oftentimes, transition-iron-carbide precipitates appear to exhibit a rodlike or needlelike morphology [2,6,7,10,12,15,16,18], but upon closer examination at high magnification, numerous transmission electron microscope (TEM) images have revealed that the ''rods'' were composed of individual, closely spaced, equiaxed precipitates of very small size (e.g., less than 10 nm) [2, 8-12, 15, 16, 18].…”

Section: Introductionmentioning

confidence: 61%

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Further Observations of Linear Arrays of Transition-Iron-Carbide Precipitates in Tempered 4340 Steel

Thompson

2018

Metallogr. Microstruct. Anal.

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4340 steel was quenched to form lath martensite and then tempered at 200°C for 1 h. Microstructural features of a large lath were examined in detail via transmission electron microscopy, including bright-field imaging, centered-dark-field imaging, and electron diffraction. Linear arrays of transition-iron-carbide precipitate were characterized. Rodlike arrays measured about 100 nm in length and were aligned predominantly along \100[ martensite directions. The rodlike arrays consisted of small, closely spaced, nearly equiaxed transition-iron-carbide precipitates of less than 10 nm in diameter. Kinks in the rodlike arrays resulted is deviations from \100[ directions by about 20°-30°. A less-common type of linear array measured 500 nm in length. These longer features were aggregates of kinked rodlike arrays that seemed to be ''attached'' by kinked segments, again at 20°-30°from \100[ martensite directions. Transition-iron-carbide precipitates showed little if any association with martensite matrix dislocations that were aligned predominantly along \111[ directions. A hypothesis was offered in which precipitates aligned along \100[ martensite directions are a remnant of spinodal decomposition that develops planar modulations of high-and low-carbon regions prior to the first stage of tempering.Keywords 4340 steel Á Transition-iron-carbide precipitates Á Rodlike precipitate arrays Á Kinked segments Á Planar modulations of high-and low-carbon regions This article is an invited paper selected from presentations at ''Fifty Years of Metallography and Materials Characterization,'' a symposium celebrating the 50th Anniversary of the International Metallographic Society, held during MS&T'17, October 8-12, 2017, in Pittsburgh, Pa., and has been expanded from the original presentation.

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Section: Introductionsupporting

confidence: 56%

Section: Introductionmentioning

confidence: 61%

Further Observations of Linear Arrays of Transition-Iron-Carbide Precipitates in Tempered 4340 Steel

Thompson

2018

Metallogr. Microstruct. Anal.

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“…De Cooman and his colleagues applied internal friction measuring techniques to as‐quenched martensite and martensite subjected to low‐temperature paint baking heat treatments in 22MB5 steel . Internal friction measures the effect of short range atom and dislocation motion at periodic stresses significantly below yield stresses, which cause strain to lag stress as is commonly measured by testing in a torsion pendulum .…”

Section: High Temperature Tempering Of Lath Martensitementioning

confidence: 99%

“…There are a number of relaxation peaks associated with carbon, edge and screw dislocation movement, and carbon atom‐dislocation interactions observed during internal friction testing of as‐quenched and LTT martensite, and all disappear at high temperature tempering treatments. These mechanisms are extensively discussed . Of interest to press hardened martensite in low carbon steels, it is concluded that all carbon atoms segregate to dislocation cores during die quenching and argued that one of the relaxations may be associated with carbon atoms located outside of dislocation slip planes.…”

Section: High Temperature Tempering Of Lath Martensitementioning

confidence: 99%

Tempering of Lath Martensite in Low and Medium Carbon Steels: Assessment and Challenges

Krauß

2017

steel research int.

167

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This paper is a directed review of the microstructures and the mechanisms, by which they are formed by tempering of lath martensite in low and medium carbon steels. As-quenched martensitic structure is first reviewed, then low-temperature tempering (LTT) that produces ultrahigh strength and good toughness, and high-temperature-tempering (HTT), which can produce excellent combinations of strength, ductility, toughness, and good resistance to hydrogen embrittlement in sour gas and oil environments, are covered. It is well known that hardness decreases continuously with increasing tempering temperature, but the superimposed multiple mechanisms of microstructural changes by which the softening and its retardation occur during various stages of tempering have received little attention on the integrated scales of microstructure, substructure, and nanostructure. Thus, earlier descriptions of the reasons for softening need deeper examination. In particular, the reasons for the changes in the very fine crystal size and high dislocation density of as-quenched lath martensite produced by high temperature tempering, sometimes producing a low dislocation density, un-recrystallized, fine lath-morphology ferritic grain size, sometimes producing an equiaxed, recrystallized ferritic grain size, are not clear. Deformation behavior and mechanical properties as related to the residual components of martensitic microstructure that survive tempering are discussed. Questions remain and the use of newer techniques, such as Electron Back Scatter Diffraction and atom probe tomography, in addition to light microscopy, transmission electron microscopy, Mössbauer effect spectroscopy, and Mechanical Spectroscopy used in characterizing quench and tempered structures are noted.

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“…Several recent studies of advanced steels have provided keen insights on this topic using advanced characterization and modeling techniques to gain complementary results to those obtained from transmission electron microscopy [6][7][8][9][10][11][12]. However, careful examination of these recent additions to the literature reveals that some of the interpretations seem not to be in full agreement.…”

Section: Introductionmentioning

confidence: 99%

A Two-Tilt Analysis of Electron Diffraction Patterns from Transition-Iron-Carbide Precipitates Formed During Tempering of 4340 Steel

Thompson

2016

Metallogr. Microstruct. Anal.

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Fine-scale transition-iron-carbide precipitates in a lath martensitic microstructure of 4340 steel tempered at 200°C for 1 h were examined via imaging and electron diffraction techniques with a transmission electron microscope. Region-to-region variations were eliminated by analyzing a small volume of material (about 0.03 lm 3 ) at two tilt conditions. Geometric analyses showed that measured interplanar spacings compared favorably with accepted values from both epsilon-carbide and eta-carbide phases (within 1%), whereas measured interplanar angles were within 1-2% of accepted values. Centered-dark-field imaging identified precisely which reflections were produced from a single group of small precipitates (each about 10 nm in diameter). Consistent indexing schemes are provided for epsilon-and eta-carbide, including the proper angular relationship between the two tilt conditions. An interzonal angle of 17.9 o ± 0.1 o was determined for both candidate phases. The orientation relationship between the observed transition-iron-carbide phase and martensite was determined, and confirmed previous results reported for both carbide phases. Diffracted intensities of several reflections were estimated and compared favorably with those calculated from structure factors derived from idealized crystal structures of both transition-iron-carbide phases. All results are shown to be near-equally consistent with a hexagonal epsilon-carbide phase and an orthorhombic eta-carbide phase.

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Internal-friction analysis of dislocation–interstitial carbon interactions in press-hardened 22MnB5 steel

Cited by 30 publications

References 25 publications

Further Observations of Linear Arrays of Transition-Iron-Carbide Precipitates in Tempered 4340 Steel

Further Observations of Linear Arrays of Transition-Iron-Carbide Precipitates in Tempered 4340 Steel

Tempering of Lath Martensite in Low and Medium Carbon Steels: Assessment and Challenges

A Two-Tilt Analysis of Electron Diffraction Patterns from Transition-Iron-Carbide Precipitates Formed During Tempering of 4340 Steel

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