Transmission electron microscopy of dislocations in cementite deformed at high pressure and high temperature

Mussi, Alexandre; Ghosh, Sujoy; Garvik, N; Nzogang, Billy Clitton; Carrez, Philippe; Garruchet, Sébastien

doi:10.1080/14786435.2016.1177670

Cited by 17 publications

(12 citation statements)

References 31 publications

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“…The stress relaxation of cementite at 1250 • C and 10 GPa pressure over a period of 8 h has also revealed dislocation glide on (010)[001] with (010) [100] slip reported to be the most frequent. The [100] dislocations were found to be dissociated into [ 1 2 00] + [ 1 2 00] [46]. Ghaffarian et al [47] have conducted molecular dynamics simulations using of 16 grains of nanocrystalline cementite, but at the large strain rate of 5 × 10 8 s −1 , so their outcomes do not reproduce any of the observed experimental data other than to confirm the general expectation that grain boundary sliding may dominate deformation when the grain size is small.…”

Section: Structural Defects and Deformationmentioning

confidence: 99%

Cementite

Bhadeshia

2019

International Materials Reviews

111

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Cementite occurs in steels, in meteorites, possibly at the core of the Earth and has uses in its pure form. It's composition can deviate from Fe 3 C, but not by much because the Fe-C bond contributes to its cohesion. Its crystallographic unit cell is orthorhombic and primitive, with large lattice parameters, explaining its hardness. Many of its properties are anisotropic. Its single-crystal elastic properties have been investigated using first-principles calculations and by clever experiments. The iron atoms in the cell occupy two types of positions with different point symmetries; the four carbon atoms lodge within prismatic interstices. The structure can develop defects such as dislocations, faults and vacancies. Cementite is metallic and ferromagnetic with a Curie temperature of about 187 • C. When alloyed, metallic solutes substitute on to the iron sites; smaller atoms such as boron replace carbon at interstitial sites. This review focuses on cementite as a single phase.

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Section: Structural Defects and Deformationmentioning

confidence: 99%

Cementite

Bhadeshia

2019

International Materials Reviews

111

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“…Two methods have been developed to synthesize a large sample of a single-phase cementite. One is the use of high temperature and high pressure 13,[37][38][39][40][41][42][43][44][45][46] and the other is the sintering of mechanically alloyed powder 26,[47][48][49] as will be described in detail later. In addition to these four types of samples, there are samples prepared by special techniques, including single-phase thin films 25,50) prepared by the vapor deposition method; samples in which iron and graphite are melted, crushed, and cementite is extracted and sintered; 51) cementite single-crystal foil electrolytically extracted from a pearlitic sample; 35) and a sample in which the cementite volume fraction is locally increased by carburization.…”

Section: Samples Used To Study the Physical Properties Of Cementitementioning

confidence: 99%

“…This method is popular among geophysicists. 13,[37][38][39][40][41][42][43][44][45][46] In the Fe-C binary system, the cementite phase is metastable at all temperatures under one atm. Because the diffusion rate of carbon in liquid iron is very high, it is not possible to obtain a sample of single-phase cementite by solidification under normal pressure.…”

Section: Sample Preparation Using High Temperature Andmentioning

confidence: 99%

Mechanical Properties of Cementite

Umemoto

Ohtsuka

2022

ISIJ Int.

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This review focuses on the mechanical properties of single-phase cementite. The mechanical properties of interest are 1) sound velocity, 2) elastic constants, 3) hardness, 4) plastic deformation mechanism, 5) wear, 6) fracture toughness, and 7) crystal orientation anisotropy. The effects of temperature, magnetic transition, and alloying elements on the sound velocity, elastic constants, and hardness were reviewed. Furthermore, experimental values of the above mechanical properties as well as other parameters, such as the specimen shape, the quantity of alloying elements, and the measurement method, were collected. A large variation was observed in the reported experimental values. The main reason for this is that cementite is metastable, and it is difficult to prepare large single-phase samples. Other factors, such as sample shape, measurement method, alloying element, magnetic transformation, and crystal orientation anisotropy, also influenced the measured values. Studies using first-principles calculations of cementite were also reviewed. The crystal orientation anisotropy of each elastic constant of single-crystal cementite based on the first-principles calculations are summarized, and its comparison with the experimental results is discussed. By comparing the elastic constants obtained by the first-principles calculations with the measured values, the former values of Young's modulus and shear modulus are several % and bulk modulus and Poisson's ratio are several tens of % larger than those of the latter. This is thought to be because of the difference in temperature between 0 K (first-principles calculations) and room temperature (measured value), and theoretical and experimental studies in which the temperature is changed are expected.

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“…На втором этапе при деформации в области температуры 600°С отмечается легкое скольжение дислокаций, которое может способствовать диссипации энергии [17]. При этом, как и в первом случае, скольжение может сопровождаться появлением новых дефектов [18,19].…”

Section: результаты и обсуждениеunclassified

Features of the carbide phase degradation under heating and deformation

et al. 2021

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The present work reflects the results of comprehensive studies of the carbide phase behavior (cementite) in cast irons, which are widely used as a forming tool in metallurgy. This structural component determines the stable operation of the tool in production. Due to the development of new scientific approaches, special methods of structure variability analysis are being developed. Such methods allow one to have a deep look into the processes that determine the nature of degradation phenomena, including those occurring in the carbide phase. In this work, we use the results of the new techniques, which made it possible to identify degradation processes occurring inside the massive inclusions of the carbide phase of chromium-nickel cast iron during deformations at high temperatures (400 -600°C). Here we report the significant instability of the carbide phase revealed under such processing conditions. Basing on the optical-mathematical analysis of the obtained SEM microstructure images, we show that such a carbide phase degrades under the local deformations. At the first stage of deformation, the creation of local stresses is intensified, while the subgrain boundaries and individual defects are being formed. Such individual defects (dislocations) define the degree of carbon and iron diffusion which determines the formation of a number of new phases: ferrite with various carbon saturation values, bainite, carbides of nonstoichiometric composition (such as FeC and Fe x C y ).We also analyze the paired and triple interactions between these new phases. The influence of localization of the deformations on easy sliding of dislocations is considered. As it occurs, this process is accompanied by a decrease in the dispersion of the formed new ferrite and carbide phases, as well as in their mutual interactions. However, we show that when dislocations slip, the new ones appear. As a result, energy dissipation occurs. The obtained qualitative and quantitative representation of the carbide phase degradation during heating and deformation can be used to develop new technological processes of the production and hardening of such a material with a specific purpose taken into account.

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Transmission electron microscopy of dislocations in cementite deformed at high pressure and high temperature

Cited by 17 publications

References 31 publications

Cementite

Cementite

Mechanical Properties of Cementite

Features of the carbide phase degradation under heating and deformation

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