The Experts below are selected from a list of 4611 Experts worldwide ranked by ideXlab platform
S. H. Song - One of the best experts on this subject based on the ideXlab platform.
-
non equilibrium phosphorus Grain Boundary Segregation and its effect on embrittlement in a niobium stabilized interstitial free steel
Materials Letters, 2015Co-Authors: S. H. Song, Yu ZhaoAbstract:Abstract Grain Boundary Segregation of phosphorus in an Nb-stabilized and P-strengthened interstitial-free steel was investigated using Auger electron spectroscopy after the steel specimens were quenched from 880 °C and aged at 680 °C for different times. The Segregation initially increased with increasing aging time until reaching a maximum value and then decreased gradually to its equilibrium value with further increasing aging time, demonstrating a non-equilibrium Segregation kinetic characteristic with a critical time of around 30 min. The ductile-to-brittle transition temperatures (DBTTs) of the aged specimens were determined through fracture appearance measurements. There was a linear relationship between DBTT and phosphorus Boundary concentration ( C p , at%): DBTT(°C)=4.39 C p −64.06, suggesting that a P-strengthened IF steel should avoid slow cooling or staying in the intermediate temperature range so as to avoid apparent phosphorus Grain Boundary Segregation and in turn to avoid embrittling.
-
relation of ductile to brittle transition temperature to phosphorus Grain Boundary Segregation for a ti stabilized interstitial free steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011Co-Authors: Xianjue Chen, S. H. Song, L.-q. Weng, Shujuan Liu, Kun WangAbstract:Abstract Equilibrium Grain Boundary Segregation of phosphorus in a Ti-stabilized interstitial free (IF) steel is measured using Auger electron spectroscopy (AES) after the specimens are aged for adequate time at different temperatures between 600 and 850 °C. Based on the experimental data of equilibrium Grain Boundary Segregation along with the McLean equilibrium Segregation theory, the free energy of Segregation of phosphorus is evaluated to be ∼44.8 kJ/mol, being independent of temperature. With the AES results being combined with the ductile-to-brittle transition temperatures (DBTTs) determined by impact tests, a relationship between DBTT and phosphorus Boundary concentration is established. Predictions with the relationship indicate that cold work embrittlement may be severe if the steel is annealed at relatively low temperatures after cold rolling.
-
dependence of ductile to brittle transition temperature on phosphorus Grain Boundary Segregation for a 2 25cr1mo steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: S. H. Song, L.-q. Weng, H Zhuang, Z X YuanAbstract:Abstract Equilibrium Grain Boundary Segregation of phosphorus in a 2.25Cr1Mo steel was studied by means of Auger electron spectroscopy (AES). After quenching from 980 °C and tempering at 650 °C, the steel samples were aged for different periods of time at 560, 520 and 480 °C, respectively, followed by AES measurements. Based on the experimental values of the equilibrium Segregation levels at different temperatures along with equilibrium Segregation theories, the thermodynamic parameters of Segregation were evaluated. With the use of Charpy impact testing along with the AES results on phosphorus Grain Boundary concentration, a relationship between ductile-to-brittle transition temperature (DBTT) and phosphorus Boundary concentration was established. On the basis of this relationship, predictions of the DBTT were made through predicting the Grain Boundary Segregation of phosphorus.
-
non equilibrium Grain Boundary Segregation of phosphorus under a high applied tensile stress in a 2 25cr1mo steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: S. H. Song, Z X Yuan, L.-q. WengAbstract:Abstract Grain Boundary Segregation of phosphorus under a 350 MPa tensile stress at 520 °C in a 0.025 wt.% P-doped 2.25Cr1Mo steel, which has already been thermally equilibrated, is examined using Auger electron spectroscopy. The Segregation of phosphorus during stress ageing has a non-equilibrium characteristic, which has two phosphorus Segregation peaks over its equilibrium Segregation level, one of which is mainly due to the vacancy–phosphorus complex effect and the other due to the diffusional creep effect.
-
an auger electron spectroscopy study of phosphorus and molybdenum Grain Boundary Segregation in a 2 25cr1mo steel
Materials Characterization, 2008Co-Authors: S. H. Song, L.-q. Weng, Z X YuanAbstract:Thermodynamics of Grain Boundary Segregation of phosphorus and molybdenum in a 2.25Cr1Mo steel were investigated using Auger electron spectroscopy (AES). After quenching from 980 °C and tempering at 650 °C, the steel samples were aged for different times at 560 °C, 520 °C and 480 °C, respectively, followed by AES measurements. Based on the AES results for equilibrium Grain Boundary concentrations of phosphorus and molybdenum, it is seen that the interaction between these two elements in Segregation is weak and the free energies of Segregation are constant, being about 38 kJ/mol and 17 kJ/mol for phosphorus and molybdenum, respectively.
L.-q. Weng - One of the best experts on this subject based on the ideXlab platform.
-
relation of ductile to brittle transition temperature to phosphorus Grain Boundary Segregation for a ti stabilized interstitial free steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011Co-Authors: Xianjue Chen, S. H. Song, L.-q. Weng, Shujuan Liu, Kun WangAbstract:Abstract Equilibrium Grain Boundary Segregation of phosphorus in a Ti-stabilized interstitial free (IF) steel is measured using Auger electron spectroscopy (AES) after the specimens are aged for adequate time at different temperatures between 600 and 850 °C. Based on the experimental data of equilibrium Grain Boundary Segregation along with the McLean equilibrium Segregation theory, the free energy of Segregation of phosphorus is evaluated to be ∼44.8 kJ/mol, being independent of temperature. With the AES results being combined with the ductile-to-brittle transition temperatures (DBTTs) determined by impact tests, a relationship between DBTT and phosphorus Boundary concentration is established. Predictions with the relationship indicate that cold work embrittlement may be severe if the steel is annealed at relatively low temperatures after cold rolling.
-
dependence of ductile to brittle transition temperature on phosphorus Grain Boundary Segregation for a 2 25cr1mo steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: S. H. Song, L.-q. Weng, H Zhuang, Z X YuanAbstract:Abstract Equilibrium Grain Boundary Segregation of phosphorus in a 2.25Cr1Mo steel was studied by means of Auger electron spectroscopy (AES). After quenching from 980 °C and tempering at 650 °C, the steel samples were aged for different periods of time at 560, 520 and 480 °C, respectively, followed by AES measurements. Based on the experimental values of the equilibrium Segregation levels at different temperatures along with equilibrium Segregation theories, the thermodynamic parameters of Segregation were evaluated. With the use of Charpy impact testing along with the AES results on phosphorus Grain Boundary concentration, a relationship between ductile-to-brittle transition temperature (DBTT) and phosphorus Boundary concentration was established. On the basis of this relationship, predictions of the DBTT were made through predicting the Grain Boundary Segregation of phosphorus.
-
non equilibrium Grain Boundary Segregation of phosphorus under a high applied tensile stress in a 2 25cr1mo steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: S. H. Song, Z X Yuan, L.-q. WengAbstract:Abstract Grain Boundary Segregation of phosphorus under a 350 MPa tensile stress at 520 °C in a 0.025 wt.% P-doped 2.25Cr1Mo steel, which has already been thermally equilibrated, is examined using Auger electron spectroscopy. The Segregation of phosphorus during stress ageing has a non-equilibrium characteristic, which has two phosphorus Segregation peaks over its equilibrium Segregation level, one of which is mainly due to the vacancy–phosphorus complex effect and the other due to the diffusional creep effect.
-
an auger electron spectroscopy study of phosphorus and molybdenum Grain Boundary Segregation in a 2 25cr1mo steel
Materials Characterization, 2008Co-Authors: S. H. Song, L.-q. Weng, Z X YuanAbstract:Thermodynamics of Grain Boundary Segregation of phosphorus and molybdenum in a 2.25Cr1Mo steel were investigated using Auger electron spectroscopy (AES). After quenching from 980 °C and tempering at 650 °C, the steel samples were aged for different times at 560 °C, 520 °C and 480 °C, respectively, followed by AES measurements. Based on the AES results for equilibrium Grain Boundary concentrations of phosphorus and molybdenum, it is seen that the interaction between these two elements in Segregation is weak and the free energies of Segregation are constant, being about 38 kJ/mol and 17 kJ/mol for phosphorus and molybdenum, respectively.
-
small punch test evaluation of neutron irradiation induced embrittlement of a cr mo low alloy steel
Materials Characterization, 2004Co-Authors: S. H. Song, PHILIPPE MARMY, Peter E J Flewitt, R.g. Faulkner, L.-q. WengAbstract:Neutron-irradiation-induced embrittlement of a 2.25Cr1Mo steel is investigated by means of small punch testing along with scanning electron trucroscopy. There is an apparent irradiation-induced embrittlement effect after the steel is irradiated at about 400 degreesC for 86 days with a neutron dose rate of 1.75 X 10(-8) dpa/s. The embrittlement is mainly nonhardening embrittlement caused by impurity Grain Boundary Segregation. (C) 2004 Elsevier Inc. All rights reserved.
Christopher A Schuh - One of the best experts on this subject based on the ideXlab platform.
-
atomistic assessment of solute solute interactions during Grain Boundary Segregation
Nanomaterials, 2021Co-Authors: Thomas P Matson, Christopher A SchuhAbstract:Grain Boundary solute Segregation is becoming increasingly common as a means of stabilizing nanocrystalline alloys. Thermodynamic models for Grain Boundary Segregation have recently revealed the need for spectral information, i.e., the full distribution of environments available at the Grain Boundary during Segregation, in order to capture the essential physics of the problem for complex systems like nanocrystalline materials. However, there has been only one proposed method of extending spectral Segregation models beyond the dilute limit, and it is based on simple, fitted parameters that are not atomistically informed. In this work, we present a physically motived atomistic method to measure the full distribution of solute-solute interaction energies at the Grain boundaries in a polycrystalline environment. We then cast the results into a simple thermodynamic model, analyze the Al(Mg) system as a case study, and demonstrate strong agreement with physically rigorous hybrid Monte Carlo/molecular statics simulations. This approach provides a means of rapidly measuring key interactions for non-dilute Grain Boundary Segregation for any system with an interatomic potential.
-
thermodynamics and design of nanocrystalline alloys using Grain Boundary Segregation spectra
Acta Materialia, 2021Co-Authors: Malik Wagih, Christopher A SchuhAbstract:Abstract Solute Segregation at Grain boundaries (GBs) is a key mechanism to stabilize nanocrystalline alloys. To date, the standard approach to design and screen for nanocrystalline stability uses a simplified representation that treats the GB network as a single entity, and thus, uses a single “average” Segregation energy to characterize solute GB Segregation in an alloy. This simplification, however, fails to capture the highly anisotropic nature of GBs, which results in a spectrum of Segregation energies that can be very broad. Here, we remove this simplification, and outline more formally correct thermodynamic criteria to screen for thermodynamic stability of polycrystalline structures, accounting for the spectral nature of GBs. We proceed to apply the developed criteria to screen over 200 alloy combinations based on embedded atom method potentials. Among its benefits, this spectral approach enables strict enforcement of the third law of thermodynamics, where an average Segregation energy does not. The results of the screening are in general agreement with experimental observations.
-
stability of nanocrystalline metals the role of Grain Boundary chemistry and structure
Mrs Bulletin, 2021Co-Authors: Christopher A SchuhAbstract:Nanocrystalline metals are transitioning from laboratory curiosities to engineering materials, in large part due to advances in improving their stability, making their exceptional properties more predictable and accessible. Nanoscale Grains typically have a very strong innate tendency to coarsen, but the Grain-Boundary structure can be designed and tuned to lower its excess energy, reducing both the driving force for coarsening and the Grain-Boundary mobility. This article reviews two major strategies for achieving low-energy Grain boundaries in nanocrystalline structures. First, Grain-Boundary alloying is discussed, including Grain-Boundary Segregation and its energetic competition with the formation of second phases; with sufficient Grain-Boundary Segregation tendency it is possible to stabilize nanostructures to high temperatures. Second, methods of achieving low-energy crystallographic Grain-Boundary structures are discussed, including the formation of nanotwinned structures and relaxing Grain boundaries into low-energy structures through their interactions with partial dislocations. Both of these strategies have led to effective and implementable stable nanocrystalline materials, and point to many directions for future advancements.
-
learning Grain Boundary Segregation energy spectra in polycrystals
Nature Communications, 2020Co-Authors: Malik Wagih, Peter Mahler Larsen, Christopher A SchuhAbstract:The Segregation of solute atoms at Grain boundaries (GBs) can profoundly impact the structural properties of metallic alloys, and induce effects that range from strengthening to embrittlement. And, though known to be anisotropic, there is a limited understanding of the variation of solute Segregation tendencies across the full, multidimensional GB space, which is critically important in polycrystals where much of that space is represented. Here we develop a machine learning framework that can accurately predict the Segregation tendency-quantified by the Segregation enthalpy spectrum-of solute atoms at GB sites in polycrystals, based solely on the undecorated (pre-Segregation) local atomic environment of such sites. We proceed to use the learning framework to scan across the alloy space, and build an extensive database of Segregation energy spectra for more than 250 metal-based binary alloys. The resulting machine learning models and Segregation database are key to unlocking the full potential of GB Segregation as an alloy design tool, and enable the design of microstructures that maximize the useful impacts of Segregation.
-
mechanical alloying produces Grain Boundary Segregation in fe mg powders
Scripta Materialia, 2020Co-Authors: Dor Amram, Christopher A SchuhAbstract:Abstract Although mechanical alloying can force immiscible elements into homogeneous solid solution due to its chemically “randomizing” nature, as microstructure design of powder-processed alloys advances, other alloy configurations are also sought. Here we study ball milling of Fe–Mg alloys and obtain a heterogeneous nanostructure, with Grain boundaries decorated by solute even after reaching complete supersaturation and a steady-state Grain size. Such nanocrystalline powders having Grain Boundary Segregation in the as-milled state are particularly useful for thermal stability against Grain growth. The high diffusivity of Mg is thought to shift the competition between ballistic mixing and equilibration, permitting such a structure to form.
Z X Yuan - One of the best experts on this subject based on the ideXlab platform.
-
dependence of ductile to brittle transition temperature on phosphorus Grain Boundary Segregation for a 2 25cr1mo steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: S. H. Song, L.-q. Weng, H Zhuang, Z X YuanAbstract:Abstract Equilibrium Grain Boundary Segregation of phosphorus in a 2.25Cr1Mo steel was studied by means of Auger electron spectroscopy (AES). After quenching from 980 °C and tempering at 650 °C, the steel samples were aged for different periods of time at 560, 520 and 480 °C, respectively, followed by AES measurements. Based on the experimental values of the equilibrium Segregation levels at different temperatures along with equilibrium Segregation theories, the thermodynamic parameters of Segregation were evaluated. With the use of Charpy impact testing along with the AES results on phosphorus Grain Boundary concentration, a relationship between ductile-to-brittle transition temperature (DBTT) and phosphorus Boundary concentration was established. On the basis of this relationship, predictions of the DBTT were made through predicting the Grain Boundary Segregation of phosphorus.
-
non equilibrium Grain Boundary Segregation of phosphorus under a high applied tensile stress in a 2 25cr1mo steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: S. H. Song, Z X Yuan, L.-q. WengAbstract:Abstract Grain Boundary Segregation of phosphorus under a 350 MPa tensile stress at 520 °C in a 0.025 wt.% P-doped 2.25Cr1Mo steel, which has already been thermally equilibrated, is examined using Auger electron spectroscopy. The Segregation of phosphorus during stress ageing has a non-equilibrium characteristic, which has two phosphorus Segregation peaks over its equilibrium Segregation level, one of which is mainly due to the vacancy–phosphorus complex effect and the other due to the diffusional creep effect.
-
an auger electron spectroscopy study of phosphorus and molybdenum Grain Boundary Segregation in a 2 25cr1mo steel
Materials Characterization, 2008Co-Authors: S. H. Song, L.-q. Weng, Z X YuanAbstract:Thermodynamics of Grain Boundary Segregation of phosphorus and molybdenum in a 2.25Cr1Mo steel were investigated using Auger electron spectroscopy (AES). After quenching from 980 °C and tempering at 650 °C, the steel samples were aged for different times at 560 °C, 520 °C and 480 °C, respectively, followed by AES measurements. Based on the AES results for equilibrium Grain Boundary concentrations of phosphorus and molybdenum, it is seen that the interaction between these two elements in Segregation is weak and the free energies of Segregation are constant, being about 38 kJ/mol and 17 kJ/mol for phosphorus and molybdenum, respectively.
-
Grain Boundary Segregation of phosphorus and molybdenum in a cr mo low alloy steel
Materials Science and Technology, 2004Co-Authors: S. H. Song, Z X Yuan, D D Shen, Jie Liu, L.-q. WengAbstract:Abstract Grain Boundary Segregation of phosphorus and molybdenum during aging at 540°C after quenching from 980°C is examined for a P-doped 2.25Cr1Mo steel using Auger electron spectroscopy. The standard molar free energies of Segregation and diffusion coefficients for these two elements are determined through the measured Segregation kinetics along with the equilibrium Segregation theory in multicomponent systems. The values obtained for these parameters are discussed with comparison to those found in the literature for low alloy steels.
Pavel Lejček - One of the best experts on this subject based on the ideXlab platform.
-
entropy matters in Grain Boundary Segregation
Acta Materialia, 2021Co-Authors: Pavel Lejček, Siegfried Hofmann, Mojmír Šob, Monika VsianskaAbstract:Abstract Starting with a fairly comprehensive database on experimental results on enthalpy and entropy of Grain Boundary Segregation, the detrimental influence of ignoring the Segregation entropy term is shown for the latter as well as for additional examples of intergranular cohesion, the stability of nanoGrain size, and the Segregation enthalpy-Segregation entropy compensation effect. Furthermore, the decisive role of Segregation entropy in the transition from substitutional to interstitial Segregation with increasing temperature, and the newly explored effect of entropy-dominated Grain Boundary Segregation are presented. Despite the direct evidence of the importance of entropy in Grain Boundary Segregation, its contribution has been frequently neglected in the literature. One of the possible reasons is that the routines for a theoretical determination of the Segregation entropy are still missing. We hope that, in the near future, progress in advanced theoretical methods will substantially improve our present understanding of Grain Boundary Segregation.
-
Entropy-dominated Grain Boundary Segregation
Journal of Materials Science, 2021Co-Authors: Pavel Lejček, Siegfried HofmannAbstract:The phenomenon of entropy-dominated Grain Boundary Segregation is introduced and discussed. Numerous examples of the Grain boundaries and solutes exhibiting this phenomenon are compiled and predicted for example of α-iron-based alloys and other host materials. Consequences of entropy-dominated Grain Boundary Segregation for Grain size stabilization and intergranular embrittlement are shown. Graphical abstract
-
Entropy-Driven Grain Boundary Segregation: Prediction of the Phenomenon
'MDPI AG', 2021Co-Authors: Pavel Lejček, Siegfried HofmannAbstract:The question is formulated as to whether entropy-driven Grain Boundary Segregation can exist. Such a phenomenon would be based on the assumption that a solute can segregate at the Grain Boundary sites that exhibit positive Segregation energy (enthalpy) if the product of Segregation entropy and temperature is larger than this energy (enthalpy). The possibility of entropy-driven Grain Boundary Segregation is discussed for several model examples in iron-based systems, which can serve as indirect evidence of the phenomenon. It is shown that entropy-driven Grain Boundary Segregation would be a further step beyond the recently proposed entropy-dominated Grain Boundary Segregation as it represents solute Segregation at “anti-Segregation” sites
-
modeling Grain Boundary Segregation by prediction of all the necessary parameters
Acta Materialia, 2019Co-Authors: Pavel Lejček, Siegfried HofmannAbstract:Abstract A thermodynamic model of equilibrium Grain Boundary Segregation in real binary systems is proposed which is based on the prediction of all the necessary parameters. These parameters are (i) the standard enthalpy and (ii) the standard entropy of Grain Boundary Segregation, both related to ideal behavior, as well as (iii) the Fowler binary interaction coefficient describing the real contribution. Application of the model is shown in detail for the example of iron-based binary systems and predictions are compared to data published in the literature.
-
the significance of entropy in Grain Boundary Segregation
Materials, 2019Co-Authors: Pavel Lejček, Siegfried Hofmann, V PaidarAbstract:The role of entropy in materials science is demonstrated in this report in order to establish its importance for the example of solute Segregation at the Grain boundaries of bcc iron. We show that substantial differences in Grain Boundary chemistry arise if their composition is calculated with or without consideration of the entropic term. Another example which clearly documents the necessity of implementing the entropic term in materials science is the enthalpy-entropy compensation effect. Entropy also plays a decisive role in the anisotropy of Grain Boundary Segregation and in interface characterization. The consequences of the ambiguous determination of Grain Boundary Segregation on the prediction of materials behavior are also briefly discussed. All the mentioned examples prove the importance of entropy in the quantification of Grain Boundary Segregation and consequently of other materials properties.
