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E. J. Mittemeijer - One of the best experts on this subject based on the ideXlab platform.

  • Martensite Formation kinetics of substitutional fe 0 7at al alloy under uniaxial compressive stress
    Acta Materialia, 2015
    Co-Authors: Yongchang Liu, Chenxi Liu, Ferdinand Sommer, E. J. Mittemeijer
    Abstract:

    Abstract Differential dilatometry was applied to investigate the effect of an applied constant uniaxial compressive stress on the kinetics of the austenite (γ) → Martensite (α′) transFormation in the substitutional Fe–0.7 at.%Al alloy upon isochronal cooling/quenching with constant rate. All imposed stress levels are below the yield stresses of γ and α′ phases in the temperature range of the Martensite Formation. Albeit the start temperature of the γ → α′ transFormation remains approximately constant in the range of stress explored, the overall transFormation temperature range increases significantly with the increase of the uniaxial compressive stress. A modular phase transFormation model, adopting a model for continuous nucleation and an anisotropic thermally-activated growth model, yielding a corresponding impingement correction, was employed to extract the nucleation rate and the γ/α′-interface velocity during the transFormation. The kinetic analysis suggests that athermal nucleation and thermally activated growth govern the Martensite transFormation under the uniaxial compressive stress. More driving force is required when a larger uniaxial compressive stress is imposed, and the thus obtained velocity of the γ/α′-interface as function of temperature indicates a thermally activated growth governed by a relatively low activation energy.

  • unusual Martensite Formation kinetics in steels observation of discontinuous transFormation rates
    Acta Materialia, 2014
    Co-Authors: Sarah Loewy, Bastian Rheingans, E. J. Mittemeijer, Sai Ramudu Meka
    Abstract:

    Abstract In order to study the role of the potentially thermal activation of Martensite Formation in systems which are classically considered as “athermal”, the austenite → Martensite transFormation kinetics of a maraging steel (FeNiCoMo), forming lath Martensite, was investigated by dilatometry and differential thermal analysis (DTA), supplemented by electron backscatter diffraction, X-ray diffraction and transmission electron microscopy analysis of the microstructure. No dependence of the transFormation rate on cooling rate could be observed and thus any possible activation energy has to be very small. Dilatometry as well as DTA measurements revealed an unusual transFormation behavior during the Martensite Formation: a train of transFormation-rate maxima occurs, which was found to be reproducible for different specimens, heating rates and specimen geometries. This phenomenon was attributed to the Formation of the highly hierarchical microstructure of blocks of Martensite laths, grouped in packages of parallel blocks: the observed train of transFormation-rate maxima is caused by the simultaneous, concerted Formation of blocks in different packages in all grains. The simultaneity results from the defined Formation conditions for a block as established by the Formation of the preceding adjacent block within the package.

Jilt Sietsma - One of the best experts on this subject based on the ideXlab platform.

  • Laboratory simulation of Martensite Formation of white etching layer in rail steel
    International Journal of Fatigue, 2016
    Co-Authors: Jun Wu, Roumen H. Petrov, Meysam Naeimi, Rolf Dollevoet, Zili Li, Jilt Sietsma
    Abstract:

    White etching layer (WEL) is a frequently observed microstructural phenomenon in rail surface, formed during dynamic wheel/rail contact. It is considered as one of the main initiators for rolling contact fatigue cracks. There are several hypotheses for the Formation mechanism of WEL. However, due to the complicated wheel/rail contact conditions, none is directly proven. Currently, the most popular hypotheses refer to either Formation of martensitic WEL by phase transFormations or Formation of nanocrystalline ferritic WEL by severe plastic deFormation. In this work, WEL Formation by martensitic transFormation in R260Mn grade pearlitic rail steel was simulated by fast heating and quenching experiments. Microstructural characteristics of the simulated WEL and WEL observed in a field rail specimen were characterized by microhardness, optical microscopy, scanning electron microscopy and electron backscatter diffraction. Microstructures of the two WELs were compared and similarities in morphology were identified. Numerical simulation shows the possible temperature rise up to austenitizing temperatures. Combining comparisons of experimental simulation with observation of WEL in the rail and the thermodynamic calculations, the hypothesis for WEL Formation via martensitic transFormation is supported.

  • kinetics of Martensite Formation in plain carbon steels critical assessment of possible influence of austenite grain boundaries and autocatalysis
    Materials Science and Technology, 2014
    Co-Authors: S M C Van Bohemen, Jilt Sietsma
    Abstract:

    AbstractThe kinetics of the martensitic transFormation in Fe–0·80C has been determined from dilatometry data and shows no significant variation when the cooling rate is changed by two orders of magnitude. All kinetic data can be adequately simulated by the Koistinen and Marburger (KM) equation using a specific start temperature TKM and rate parameter αm. This finding supports the suggestion that the transFormation is athermal, and moreover, the absence of a time dependence strongly indicates that autocatalytic nucleation does not contribute to the transFormation kinetics in plain carbon steels on measurable time scales. Furthermore, dilatometry experiments with different austenitising conditions were conducted to examine the effect of the prior austenite grain size on the overall kinetics of Martensite Formation. The present results indicate that the progress of Martensite Formation beyond a fraction f = 0·15 is independent of the prior austenitising treatment. It is therefore concluded that austenite–aus...

  • combined Martensite and bainite Formation from austenite decomposition in hsla steel
    Advanced Materials Research, 2014
    Co-Authors: Elisabete Pinto Da Silva, Jilt Sietsma, Cecilia Fojer, Yvan Houbaert, Roumen Petrov
    Abstract:

    Recent studies have shown the possibility to induce time-dependent phase transFormations during isothermal treatment between the Martensite start (MS) temperature and Martensite finish (Mf,) temperature, i.e. after initial Martensite Formation. Such treatments result in specific complex microstructures consisting of bainite, Martensite and retained austenite, depending on the holding temperature and time. However, the nature of the isothermal transFormations below MS is not completely understood and issues like isothermal Formation of Martensite and bainite Formation are still under discussion. The purpose of this study is to investigate the phase transFormations from austenite, subsequent to initial Martensite Formation, during isothermal treatments at different temperatures of HSLA steel. The microstructure development was monitored by means of dilatometry and microstructural characterization of the transFormation products by Optical Microscopy, Scanning Electron Microscope, Electron Backscatter Diffraction and X-ray diffraction. The phase transFormations and complex competition and interactions between the different transFormation mechanisms are discussed.

  • in situ determination of austenite and Martensite Formation in 13cr6ni2mo supermartensitic stainless steel
    Materials Characterization, 2012
    Co-Authors: A Bojack, L. Zhao, P F Morris, Jilt Sietsma
    Abstract:

    Abstract In-situ analysis of the phase transFormations in a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) was carried out using a thermo-magnetic technique, dilatometry and high temperature X-ray diffractometry (HT-XRD). A combination of the results obtained by the three applied techniques gives a valuable insight in the phase transFormations during the austenitization treatment, including subsequent cooling, of the 13Cr6Ni2Mo supermartensitic stainless steel, where the magnetic technique offers a high accuracy in monitoring the austenite fraction. It was found by dilatometry that the austenite Formation during heating takes place in two stages, most likely caused by partitioning of Ni into austenite. The in-situ evolution of the austenite fraction is monitored by high-temperature XRD and dilatometry. The progress of Martensite Formation during cooling was described with a Koistinen–Marburger relation for the results obtained from the magnetic and dilatometer experiments. Enhanced Martensite Formation at the sample surface was detected by X-ray diffraction, which is assumed to be due to relaxation of transFormation stresses at the sample surface. Due to the high alloy content and high thermodynamic stability of austenite at room temperature, 4 vol.% of austenite was found to be stable at room temperature after the austenitization treatment.

  • α′-Martensite Formation in deep-drawn Mn-based TWIP steel
    Journal of Materials Science, 2012
    Co-Authors: R. T. Tol, Jilt Sietsma, L. Zhao, J. K. Kim, B. C. Cooman
    Abstract:

    To understand the Formation of α′-Martensite in high stacking fault energy twinning-induced plasticity steel deformed in the deep drawing mode, the existing phases were investigated using magnetic and transmission electron microscopy (TEM). Small fractions of α‘-Martensite were quantitatively determined by magnetization saturation experiments and further observed by TEM. TEM revealed the Formation of α′-Martensite at shear band and twin intersections.

Yongchang Liu - One of the best experts on this subject based on the ideXlab platform.

  • Martensite Formation kinetics of substitutional fe 0 7at al alloy under uniaxial compressive stress
    Acta Materialia, 2015
    Co-Authors: Yongchang Liu, Chenxi Liu, Ferdinand Sommer, E. J. Mittemeijer
    Abstract:

    Abstract Differential dilatometry was applied to investigate the effect of an applied constant uniaxial compressive stress on the kinetics of the austenite (γ) → Martensite (α′) transFormation in the substitutional Fe–0.7 at.%Al alloy upon isochronal cooling/quenching with constant rate. All imposed stress levels are below the yield stresses of γ and α′ phases in the temperature range of the Martensite Formation. Albeit the start temperature of the γ → α′ transFormation remains approximately constant in the range of stress explored, the overall transFormation temperature range increases significantly with the increase of the uniaxial compressive stress. A modular phase transFormation model, adopting a model for continuous nucleation and an anisotropic thermally-activated growth model, yielding a corresponding impingement correction, was employed to extract the nucleation rate and the γ/α′-interface velocity during the transFormation. The kinetic analysis suggests that athermal nucleation and thermally activated growth govern the Martensite transFormation under the uniaxial compressive stress. More driving force is required when a larger uniaxial compressive stress is imposed, and the thus obtained velocity of the γ/α′-interface as function of temperature indicates a thermally activated growth governed by a relatively low activation energy.

  • Martensite Formation kinetics of substitutional fe 0 7 at al alloy under uniaxial compressive stress
    Acta Materialia, 2015
    Co-Authors: Yongchang Liu, Eric J Mittemeijer, Chenxi Liu, Ferdinand Sommer
    Abstract:

    Abstract Differential dilatometry was applied to investigate the effect of an applied constant uniaxial compressive stress on the kinetics of the austenite (γ) → Martensite (α′) transFormation in the substitutional Fe–0.7 at.%Al alloy upon isochronal cooling/quenching with constant rate. All imposed stress levels are below the yield stresses of γ and α′ phases in the temperature range of the Martensite Formation. Albeit the start temperature of the γ → α′ transFormation remains approximately constant in the range of stress explored, the overall transFormation temperature range increases significantly with the increase of the uniaxial compressive stress. A modular phase transFormation model, adopting a model for continuous nucleation and an anisotropic thermally-activated growth model, yielding a corresponding impingement correction, was employed to extract the nucleation rate and the γ/α′-interface velocity during the transFormation. The kinetic analysis suggests that athermal nucleation and thermally activated growth govern the Martensite transFormation under the uniaxial compressive stress. More driving force is required when a larger uniaxial compressive stress is imposed, and the thus obtained velocity of the γ/α′-interface as function of temperature indicates a thermally activated growth governed by a relatively low activation energy.

  • phase transFormation behavior and microstructural control of high cr martensitic ferritic heat resistant steels for power and nuclear plants a review
    Journal of Materials Science & Technology, 2015
    Co-Authors: Xiaosheng Zhou, Chenxi Liu, Yongchang Liu
    Abstract:

    The martensitic/ferritic steels have been used as boiler and turbine materials in power plants, and also been selected as potential materials for structural materials in nuclear reactors. In this paper, the kinetic analysis of the Martensite Formation and microstructural control of high-Cr martensitic/ferritic steels are reviewed. A modular approach, incorporating Fisher partitioning nucleation and anisotropic growth for impingement, was proposed to describe the Martensite Formation kinetics under different cooling rates. The kinetic analysis suggested a thermal-activated growth feature occurring during the martensitic transFormation of martensitic steels. The microstructure can be tuned by composition optimization and various combinations of heat treatment parameters (temperature, time, severe and minor deFormation). For the application in power plant, the potential of boundary-design, refinement of original austenite grain size and the final martensitic lath, pinning effect of stable carbides, in improving the performances of martensitic/ferritic steels at elevated temperatures should be investigated more thoroughly. Furthermore, efforts should be made to explore the effects of retained austenite on the improvement of high-temperature creep strength. For the application of nuclear plants, attempts should also be made to produce Fe powders with uniformly distributed oxide particles by chemical reactions.

  • kinetics of Martensite Formation in substitutional fe al alloys dilatometric analysis
    Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2013
    Co-Authors: Yongchang Liu, Eric J Mittemeijer, Ferdinand Sommer, Lifang Zhang
    Abstract:

    High-resolution differential dilatometry was employed to study the kinetics of the Martensite Formation upon isochronal cooling/quenching of substitutional Fe-(0.5, 0.7, and 1.0) at. pct Al alloys at fast cooling/quenching rates in the range of 17 K (17 °C) through 100 K (100 °C) s−1, with an emphasis on the as-yet unexpected influence of cooling/quenching rate. The Martensite transFormation initiated at nearly the same temperature (i.e., the $$ M_{\text{S}} $$ temperature) in the ferrite-phase region for all cooling/quenching rates applied, which indicates athermal nucleation: the chemical driving force governs the initiation of the nucleation of the Martensite plates. Variation of the cooling/quenching rates revealed two principal kinetic features: both the temperature ranges passed during transFormation and the grain size of the product Martensite increase with the increase of cooling/quenching rates. A modular phase-transFormation model, incorporating a classic partitioning analysis for nucleation and anisotropic growth for impingement, has been employed to extract the velocity of the migrating Martensite/austenite interface from the dilatometric data. The thus obtained velocity of the Martensite/austenite interface as function of temperature indicates a thermally activated growth governed by relatively lower activation energy, as determined by evaluation of the Martensite-Formation-rate maximum as function of cooling/quenching rate.

  • Martensite transFormation in the modified high cr ferritic heat resistant steel during continuous cooling
    Journal of Materials Research, 2012
    Co-Authors: Qiuzhi Gao, Yongchang Liu, Zesheng Yan
    Abstract:

    The thermal dilation experiment and the Martensite transFormation features of modified high Cr ferritic heat-resistant steel upon continuous cooling were explored at various cooling rates. The “spread” Martensite transFormation model was introduced to investigate the influence of the cooling rate applied on the Martensite transFormation behaviors. The Martensite fraction, Martensite Formation rate, and the density of Martensite laths were obtained as a function of cooling rate. Both the onset and offset temperatures of the Martensite transFormation decrease with the increase of cooling rate, and the Martensite Formation rate bursts at the beginning of transFormation and then reaches a peak rapidly. The fitted data based on the proposed kinetic model indicated that the aspect ratio of Martensite lath decreases, instead the density of Martensite laths increases, with the increase of cooling rate.

Eric J Mittemeijer - One of the best experts on this subject based on the ideXlab platform.

  • transFormation rate maxima during lath Martensite Formation plastic vs elastic shape strain accommodation
    Philosophical Magazine, 2016
    Co-Authors: Sarah Loewy, Bastian Rheingans, Eric J Mittemeijer
    Abstract:

    AbstractRecently, a modulated Formation behaviour of lath Martensite in Fe–Ni(-based) alloys was observed, exhibiting a series of transFormation-rate maxima. This peculiar transFormation behaviour was explained on the basis of the hierarchical microstructure of lath Martensite, minimising the net shape strain associated with Martensite Formation, by a block-by-block Formation of Martensite packages occurring simultaneously in all packages. In the present work, the martensitic transFormation upon slow cooling of two Fe–Ni alloys, containing 22 and 25 at.% of Ni, respectively, was investigated by high-resolution dilatometry with the aim of identifying the influence of alloy composition on the modulated transFormation behaviour. The differences observed for the two alloys, a more rapid sequence of the transFormation-rate maxima and a narrower temperature range in case of Fe-25 at.% Ni, can be explained consistently as a consequence of the lower transFormation temperatures in Fe-25 at.% Ni, highlighting the r...

  • Martensite Formation kinetics of substitutional fe 0 7 at al alloy under uniaxial compressive stress
    Acta Materialia, 2015
    Co-Authors: Yongchang Liu, Eric J Mittemeijer, Chenxi Liu, Ferdinand Sommer
    Abstract:

    Abstract Differential dilatometry was applied to investigate the effect of an applied constant uniaxial compressive stress on the kinetics of the austenite (γ) → Martensite (α′) transFormation in the substitutional Fe–0.7 at.%Al alloy upon isochronal cooling/quenching with constant rate. All imposed stress levels are below the yield stresses of γ and α′ phases in the temperature range of the Martensite Formation. Albeit the start temperature of the γ → α′ transFormation remains approximately constant in the range of stress explored, the overall transFormation temperature range increases significantly with the increase of the uniaxial compressive stress. A modular phase transFormation model, adopting a model for continuous nucleation and an anisotropic thermally-activated growth model, yielding a corresponding impingement correction, was employed to extract the nucleation rate and the γ/α′-interface velocity during the transFormation. The kinetic analysis suggests that athermal nucleation and thermally activated growth govern the Martensite transFormation under the uniaxial compressive stress. More driving force is required when a larger uniaxial compressive stress is imposed, and the thus obtained velocity of the γ/α′-interface as function of temperature indicates a thermally activated growth governed by a relatively low activation energy.

  • Modulated Martensite Formation behavior in Fe–Ni-based alloys; athermal and thermally activated mechanisms
    Journal of Materials Research, 2015
    Co-Authors: Sarah Loewy, Bastian Rheingans, Sai Ramudu Meka, Eric J Mittemeijer
    Abstract:

    The martensitic transFormation of Fe–22 wt% Ni austenite was investigated by high-resolution dilatometry as well as differential thermal analysis. Macroscopically discontinuous Formation of lath Martensite was observed, manifested in a train of transFormation-rate maxima. It is proposed that the modulation of the transFormation rate is caused by simultaneous Formation of blocks in different Martensite packages. The origin of simultaneity is ascribed to the interplay of chemical driving force, developing strain energy, and its relaxation upon sufficiently slow cooling. The transFormation-rate maxima become more distinct with decreasing cooling rate (CR), clearly indicating the involvement of a thermally activated process in Martensite Formation. Quantitative analysis of the microstructure of differently cooled specimens revealed smaller Martensite block sizes for higher CRs. All observations are compatible with athermal nucleation and thermally activated growth. (Local) strain relaxation in the austenite was identified as the involved thermally activated mechanism.

  • kinetics of Martensite Formation in substitutional fe al alloys dilatometric analysis
    Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2013
    Co-Authors: Yongchang Liu, Eric J Mittemeijer, Ferdinand Sommer, Lifang Zhang
    Abstract:

    High-resolution differential dilatometry was employed to study the kinetics of the Martensite Formation upon isochronal cooling/quenching of substitutional Fe-(0.5, 0.7, and 1.0) at. pct Al alloys at fast cooling/quenching rates in the range of 17 K (17 °C) through 100 K (100 °C) s−1, with an emphasis on the as-yet unexpected influence of cooling/quenching rate. The Martensite transFormation initiated at nearly the same temperature (i.e., the $$ M_{\text{S}} $$ temperature) in the ferrite-phase region for all cooling/quenching rates applied, which indicates athermal nucleation: the chemical driving force governs the initiation of the nucleation of the Martensite plates. Variation of the cooling/quenching rates revealed two principal kinetic features: both the temperature ranges passed during transFormation and the grain size of the product Martensite increase with the increase of cooling/quenching rates. A modular phase-transFormation model, incorporating a classic partitioning analysis for nucleation and anisotropic growth for impingement, has been employed to extract the velocity of the migrating Martensite/austenite interface from the dilatometric data. The thus obtained velocity of the Martensite/austenite interface as function of temperature indicates a thermally activated growth governed by relatively lower activation energy, as determined by evaluation of the Martensite-Formation-rate maximum as function of cooling/quenching rate.

E I Galindonava - One of the best experts on this subject based on the ideXlab platform.

  • on the prediction of Martensite Formation in metals
    Scripta Materialia, 2017
    Co-Authors: E I Galindonava
    Abstract:

    Abstract A new approach to predict athermal Martensite Formation in metals is presented. It is based on computing the driving force of the transFormation including a strain energy term induced by atomic shear displacements and energy terms due to substitutional and interstitial lattice distortions. The model is applied to prescribe the Martensite and austenite start temperatures in Fe-, Ti- and Co-based alloys with no adjustable parameters. Expressions for M s variations with composition are derived for multicomponent systems. The transFormation temperature hysteresis is predicted in Co alloys showing that this approximation can be used to design alloys with the shape memory effect.

  • modelling and design of stress induced Martensite Formation in metastable β ti alloys
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014
    Co-Authors: Suresh Neelakantan, E I Galindonava, David Martin, Jesus Chao, P E J Riveradiazdelcastillo
    Abstract:

    Abstract The temperature dependence of the stress-induced Martensite (SIM) Formation in a Ti–10V–2Fe–3Al (Ti-1023) alloy under compressive loading has been studied. At low temperatures, the stress level at which Martensite starts to form increases linearly with the deFormation temperature, while the stress at which the deFormation switches to regular plastic deFormation is roughly temperature independent. A thermostatistical model for dislocation evolution is employed to describe deFormation twinning in Martensite. Combined effects of twinning induced plasticity and solid solution strengthening are considered in terms of temperature variations. The SIM effect disappears on deFormation at temperatures beyond ~ 233 ° C , which is close to the predicted Ms temperature of 240 °C. The thermostatistical model predicts a transition from twinned Martensite to pure slip at 250 °C. By providing a model to predict the Martensite Formation, and by describing deFormation twinning, the present work provides a number of tools that may be employed to conceive new titanium alloys combining improved strength and ductility.