Experimental and computational study of cementite precipitation in tempered martensite

Zamberger, Sabine; Whitmore, Lawrence; Krisam, Sabine; Wójcik, Tomasz; Kozeschnik, Ernst

doi:10.1088/0965-0393/23/5/055012

Cited by 19 publications

(13 citation statements)

References 51 publications

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“…During tempering, precipitation of various carbides or nitrides accompanied by microstructural recovery or recrystallization controls the development of the properties such as strength, toughness, and creep resistance in both plain carbon and alloy steels [1][2][3][4][5][6][7]. Cementite (M 3 C) is one of the important types of precipitates due to its strong effect on mechanical properties by depleting carbon from the matrix and potential precipitation hardening [4][5][6][7][8], and moreover, precipitation of M 3 C during tempering is strongly related to the evolution of other types of carbides in alloy steels [8][9][10][11][12], and it has therefore attracted plenty of attention [1][2][3][4][5][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…In the early stages of precipitation, the focus of this report, the nucleation rate and diffusion are generally rate controlling [5,6]. In binary Fe-C steels, the growth of M 3 C is controlled by the coupled diffusion of C and Fe [1,3,[13][14][15][16][17], while in Fe-C-X ternary steels, the added substitutional element generally retards the growth of M 3 C significantly [10,[18][19][20][21][22]. When modeling the growth of M 3 C, it is considered important to impose the right local condition at the interface between matrix and precipitates [3,10].…”

Section: Introductionmentioning

confidence: 99%

“…In binary Fe-C steels, the growth of M 3 C is controlled by the coupled diffusion of C and Fe [1,3,[13][14][15][16][17], while in Fe-C-X ternary steels, the added substitutional element generally retards the growth of M 3 C significantly [10,[18][19][20][21][22]. When modeling the growth of M 3 C, it is considered important to impose the right local condition at the interface between matrix and precipitates [3,10]. One of the following three assumptions is generally used: (1) partitioning local equilibrium (PLE) where local equilibrium is maintained at the interface, (2) paraequilibrium (PE) [6,7] where only carbon is at equilibrium at the interface and the precipitate inherits the substitutional solute content from the matrix and (3) non-partitioning local equilibrium (NPLE) [5] where the growing phase also inherits the substitutional solute content but grows under local equilibrium at the interface for both carbon and substitutional solutes.…”

Section: Introductionmentioning

confidence: 99%

“…The above-mentioned reports on low-temperature tempering of M 3 C suggest that nucleation and growth depends on the temperature and alloying, leading to different compositions of the initial nucleus and the early growth is controlled by PE, while later stages of growth are influenced by the diffusion of substitutional elements to and within the M 3 C. With increasing temperature, the controlling mechanism of growth has been proposed to change from PE to NPLE [10,22,30], and in the case of pearlitic and upper-bainitic phase transformations this transition from PE to NPLE has been reported [10,22,31]. In the case of M 3 C precipitation, a systematic experimental and modeling work is lacking to clarify the interface condition during early stages of precipitation of M 3 C at high tempering temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Early stages of cementite precipitation during tempering of 1C–1Cr martensitic steel

et al. 2019

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The precipitation of cementite (M 3 C) from as-quenched martensite during tempering at 500 and 700°C was investigated in a Fe-1C-1Cr (wt%) alloy. Tempering for a short duration at 700°C results in a Cr/Fe ratio in the core region of M 3 C precipitates which is equal to the bulk alloy composition, while a shell on the surface of the precipitates exhibits a higher Cr concentration. With a prolonged tempering up to 5 h, the shell concentration gradually increases toward the equilibrium value, but the core region has not yet reached the equilibrium value. After tempering for 5 s at 500°C, there is no Cr enrichment found at the M 3 C-matrix interface, while a transition to partitioning of Cr is found during the first 5 min of tempering at 500°C. These experimental results indicate that M 3 C grows without significant partitioning of substitutional elements at both temperatures initially, i.e., growth is carbon diffusion controlled. This stage is, however, very short, and soon after 5 s at 700°C and 5 min at 500°C, Cr diffusion becomes important. Calculations using the diffusion simulation software DICTRA and precipitation simulation software TC-PRISMA were performed. The diffusion simulations using the local equilibrium interface condition show excellent agreement with experiments concerning Cr enrichment of the particles, but the size evolution is overestimated. On the other hand, the precipitation simulations underestimate the size evolution. It is suggested that a major improvement in the precipitation model could be achieved by implementing a modified nucleation model that considers nucleation far from the equilibrium composition.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Early stages of cementite precipitation during tempering of 1C–1Cr martensitic steel

et al. 2019

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“…For austenite, a dislocation density of 10 11 m -2 was adopted from [45]. For martensite, the static recovery part of a state-parameter-based recrystallization model from [50,51] was implemented. The evolution of dislocation density in subgrain interiors can subsequently be described by Eq.…”

Section: Microstructural Settingsmentioning

confidence: 99%

Thermodynamic Modelling and Microstructural Study of Z-Phase Formation in a Ta-Alloyed Martensitic Steel

et al. 2021

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A thermokinetic computational framework for precipitate transformation simulations in Ta-containing martensitic Z-steels was developed, including Calphad thermodynamics, diffusion mobility data from the literature, and a kinetic parameter setup that considered precipitation sites, interfacial energies and dislocation density evolution. The thermodynamics of Ta-containing subsystems were assessed by atomic solubility data and enthalpies from the literature as well as from the experimental dissolution temperature of Ta-based Z-phase CrTaN obtained from differential scanning calorimetry. Accompanied by a comprehensive transmission electron microscopy analysis of the microstructure, thermokinetic precipitation simulations with a wide-ranging and well-documented set of input parameters were carried out in MatCalc for one sample alloy. A special focus was placed on modelling the transformation of MX into the Z-phase, which was driven by Cr diffusion. The simulation results showed excellent agreement with experimental data in regard to size, number density and chemical composition of the precipitates, showing the usability of the developed thermokinetic simulation framework.

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Lath martensite substructure evolution in low-carbon microalloyed steels

2022

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Lath martensite substructures in as-quenched plain carbon steels exhibit dislocation-like contrast in the transmission electron microscope. More recent observations reported internal twins and nanoscale auto-tempered intra-lath carbides as additional lath substructures in ultra-low-C binary Fe–C steels. Modern microalloyed steels often have similar ultra-low C contents besides microalloying elements like Ti, Nb or V and, more recently, Mo, to achieve high strength, toughness and weldability. Nonetheless, little is known about the lath substructure evolution in the as-quenched state of microalloyed steels. This study investigates the hierarchical martensite substructure evolution post-quenching of microalloyed Nb and NbMo steels with 0.1 wt% C. Hierarchical microstructure characterization was done using scanning and transmission electron microscopy, and electron backscatter diffraction methods including parent grain reconstructions with MTEX. Thermokinetic simulations using MatCalc to determine the carbide evolution during auto-tempering were corroborated with site-specific transmission electron microscopy. Mo addition led to lowering of the martensite start temperature, yet the Nb steel showed a finer hierarchical microstructure. Finer laths with in-lath dislocations, short and long twins, and lath boundary decoration of carbides were found in the Nb steel. Conversely, laths in the NbMo were wider, with frequent intra-lath auto-tempered precipitates in the vicinity of dislocations, without twins.

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Experimental and computational study of cementite precipitation in tempered martensite

Cited by 19 publications

References 51 publications

Early stages of cementite precipitation during tempering of 1C–1Cr martensitic steel

Early stages of cementite precipitation during tempering of 1C–1Cr martensitic steel

Thermodynamic Modelling and Microstructural Study of Z-Phase Formation in a Ta-Alloyed Martensitic Steel

Lath martensite substructure evolution in low-carbon microalloyed steels

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