Stockholm, Sweden
Stockholm, Sweden

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Agency: Cordis | Branch: FP7 | Program: CSA-CA | Phase: NMP.2013.2.3-2 | Award Amount: 880.60K | Year: 2013

Scope of this proposal is to establish a network of stakeholders - an Integrative Computational Materials Engineering expert group (ICMEg) - aiming at the creation of an open, global standard for information exchange between a heterogeneous variety of commercial and academic simulation tools. The vision of the ICMEg proposal is a new strategy of materials and process development, where a variety of academic and commercial simulation tools present and future can be easily combined across different process steps and bridging several length scales in a plug&play type architecture being based on an object oriented, standardized information exchange. Multi-scale in this context covers electronic, atomistic,mesoscopic and continuum models The Mission of ICMEg is to establish and to maintain a network of contacts to (1) simulation software providers around the world (2) governmental and international standardization authorities (3) ICME type users of simulation software (4) different associations in the area of materials and processing (5) academic developers of simulation software to define an ICME language in form of an open and standardized communication protocol to stimulate knowledge sharing in the field of multiscale materials design to communicate this standard worldwide to make it widely accepted to discuss and to decide about future amendments to the initial standard to establish a legal body for a sustainable further development The Approach of ICMEg to realize both its vision and its mission is to create a global network of all stakeholders in the area of ICME software and users by identifying all actors in the field of ICME related simulations creating an inventory of these stakeholders networking of all identified stakeholders in two international conferences composing a directory of all available simulation approaches establishing a common language for standardized information exchange secure sustainable further the common language by foundation of an international association identifying missing models and functionalities and proposing a roadmap for their development

Xiong W.,KTH Royal Institute of Technology | Xiong W.,Central South University | Selleby M.,KTH Royal Institute of Technology | Chen Q.,Thermo Calc Software | And 2 more authors.
Critical Reviews in Solid State and Materials Sciences | Year: 2010

Phase equilibria and thermodynamic properties in the Fe-Cr system have been reviewed comprehensively based on experimental information and available computer simulations in different scales. The evaluated phase equilibria show significant differences from the currently accepted thermodynamic description by CALPHAD (calculation of phase diagram) approach. The thermodynamic properties of the Fe-Cr system, such as heat capacity, enthalpy, and activity, have been evaluated in reported experiments. The experiments on phase separation in the Fe-Cr system have also been critically reviewed with a focus on spinodal decomposition. The reported data are concentrated in the temperature range from 673 to 823 K. In addition, there is a transition region between spinodal decomposition and nucleation regimes within the composition limit from 24 to 36.3 at.% Cr and the temperature range between 700 and 830 K. In view of the importance of magnetism in the Fe-Cr system, some inadequacies of the currently used thermodynamic description are pointed out in addition to some problems with the current magnetic model. Remaining issues on the thermodynamics of the Fe-Cr system have been elaborated for future refinement of the thermodynamic description of the Fe-Cr system. According to the present review, the melting temperature of Cr is recommended to be about 2136 K, which is 44 K lower than the value adopted in the research community on thermodynamics, such as the Scientific Group Thermodata Europe. © 2010 Taylor and Francis Group, LLC.

Xiong W.,KTH Royal Institute of Technology | Chen Q.,Thermo Calc Software | Korzhavyi P.A.,KTH Royal Institute of Technology | Selleby M.,KTH Royal Institute of Technology
Calphad: Computer Coupling of Phase Diagrams and Thermochemistry | Year: 2012

The standard magnetic model in the current CALPHAD modeling is based on the Inden-Hillert-Jarl model and an empirical constraint due to Weiss and Tauer that can be used to connect ferromagnetism and antiferromagnetism. In this work, we demonstrate that many artifacts can be produced by using the current approach when modeling systems with elements of different forms of magnetism. We then propose several simple measures to improve the standard magnetic model so that a physically and numerically correct and more accurate description for the Gibbs energy of magnetic ordering can be obtained in normal situations. Especially, we have assumed that each magnetic phase always possesses both ferromagnetic and antiferromagnetic states, with one of them stable and the other non-stable. The concept of 'effective magnetic moment' has also been introduced as a measure of the maximum magnetic entropy. A case study on the Al-Cr-Fe system has been performed at 0 K showing the importance of reasonable description of the magnetic phase diagrams. It has been stressed that the extended magnetic model in this work can be further employed for bridging atomistic and phenomenological modeling for multi-scale simulation. © 2012 Elsevier Ltd. All rights reserved.

Hallstrom S.,Thermo Calc Software | Hoglund L.,KTH Royal Institute of Technology | Gren J.,KTH Royal Institute of Technology
Acta Materialia | Year: 2011

The vacancy model of diffusion is applied to magnetite and hematite, and mathematical expressions for the iron flux in the lattice-fixed frame of reference, as a function of the defect structure, are presented. The defect structures, i.e. the vacancy content on the different type of sites, and the thermodynamic factors are calculated from the available Calphad type of thermodynamic descriptions for the oxides. Expressions for Fe tracer diffusion coefficients are derived and the relations between mobility and tracer diffusivity are given. The mobilities are fitted by a least-squares optimization to experimental data on tracer diffusion from the literature. For magnetite, an excellent representation of the experimental tracer data is achieved together with a satisfactory description of the sparse chemical diffusion data available. For hematite, the experimental scatter is very large and anomalous large frequency factors and activation energies have been reported. In the present report a compromise is suggested. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Xiong W.,KTH Royal Institute of Technology | Hedstrom P.,KTH Royal Institute of Technology | Selleby M.,KTH Royal Institute of Technology | Odqvist J.,KTH Royal Institute of Technology | And 2 more authors.
Calphad: Computer Coupling of Phase Diagrams and Thermochemistry | Year: 2011

A thermodynamic modeling of the FeCr system down to 0 K is performed on the basis of our recent comprehensive review of this binary system [W. Xiong, M. Selleby, Q. Chen, J. Odqvist, Y. Du, Evaluation of phase equilibria and thermochemical properties in the FeCr system, Crit. Rev. Solid State Mater. Sci. 35 (2010) 125152]. The model predicts a sign change for the magnetic ordering energy of mixing rather than the enthalpy of mixing in the bcc phase at 0 K. Designed key experiments are performed not only to check the validity of the present modeling but also to assist in understanding the mechanism for spinodal decomposition of the FeCr alloy. Heat capacities and Curie temperatures of several Fe-rich alloys are determined between 320 and 1093 K by employing differential scanning calorimetry. The measured heat capacities are found to be in remarkable agreement with the prediction based on the present modeling. Microstructural patterns and frequency distribution diagrams of Cr are studied in alloys containing 26.65, 31.95, and 37.76 at.% Cr by using atom probe tomography. The observed phase separation results correspond well with our model-predicted boundary for the spinodal decomposition. Interestingly, a horn on the Cr-rich spinodal boundary is predicted below 200 K for the first time. This work demonstrates a way to bridge the ab initio calculations and CALPHAD approach. © 2011 Elsevier Ltd. All rights reserved.

Zhu Z.,University of Oxford | Hoglund L.,KTH Royal Institute of Technology | Larsson H.,Thermo Calc Software | Reed R.C.,University of Oxford
Acta Materialia | Year: 2015

The multicomponent composition space pertinent to the single crystal nickel-based superalloys is mapped and searched, using computational modelling. A resolution of 0.1 wt.% for the alloying elements is assumed, consistent with manufacturing practice. Databases are constructed of alloy compositions which are predicted to be of promising microstructural architecture: e.g. equal fractions of the γ and γ′ phases. These may be regarded as maps - one might term them genomes - of this class of structural alloy. By combining the databases with additional composition-dependent property models, it is demonstrated that compositions can be identified which - subject to the accuracy and limitations of the sub-models - are likely to prove optimal, e.g. on the basis of their creep resistance, density and cost. The methods circumvent the need for the traditional empirically-driven approaches to alloy design. © 2015 Acta Materialia Inc.

Uberuaga B.P.,Los Alamos National Laboratory | Tang M.,Los Alamos National Laboratory | Jiang C.,Thermo Calc Software | Valdez J.A.,Los Alamos National Laboratory | And 3 more authors.
Nature Communications | Year: 2015

Understanding and predicting radiation damage evolution in complex materials is crucial for developing next-generation nuclear energy sources. Here, using a combination of ion beam irradiation, transmission electron microscopy and X-ray diffraction, we show that, contrary to the behaviour observed in pyrochlores, the amorphization resistance of spinel compounds correlates directly with the energy to disorder the structure. Using a combination of atomistic simulation techniques, we ascribe this behaviour to structural defects on the cation sublattice that are present in spinel but not in pyrochlore. Specifically, because of these structural defects, there are kinetic pathways for the relaxation of disorder in spinel that are absent in pyrochlore. This leads to a direct correlation between amorphization resistance and disordering energetics in spinel, the opposite of that observed in pyrochlores. These results provide new insight into the origins of amorphization resistance in complex oxides beyond fluorite derivatives. © 2015 Macmillan Publishers Limited All rights reserved.

Zhang L.,Central South University | Zhang L.,Ruhr University Bochum | Du Y.,Central South University | Steinbach I.,Ruhr University Bochum | And 2 more authors.
Acta Materialia | Year: 2010

A systematical investigation of the diffusivities in an Al-Fe-Ni melt was presented. Based on the experimental and theoretical data about diffusivities, the temperature- and composition-dependent atomic mobilities were evaluated for the elements in Al-Ni, Al-Fe, Fe-Ni and Al-Fe-Ni melts via an effective approach. Most of the reported diffusivities can be reproduced well by the obtained atomic mobilities. In particular, for the first time the ternary diffusivity of the liquid in a ternary system is described in conjunction with the established atomic mobilities. The effect of the atomic mobilities in a liquid on microstructure and microsegregation during solidification was demonstrated with one Al-Ni binary alloy. The simulation results indicate that accurate databases of mobilities in the liquid phase are much needed for the quantitative simulation of microstructural evolution during solidification by using various approaches, including DICTRA and the phase-field method. © 2010 Acta Materialia Inc.

Larsson H.,Thermo Calc Software
Calphad: Computer Coupling of Phase Diagrams and Thermochemistry | Year: 2014

Two previously suggested simulation models, for multiphase simulations (Larsson and Engström, 2006; Larsson and Höglund, 2009) and diffusion controlled growth (Larsson and Reed, 2008), respectively, are unified to form a generalized model for 1D simulations of diffusion controlled growth under local equilibrium conditions where multiple phases are allowed on either side of an interface. © 2014 Elsevier Ltd. All rights reserved.

Software related to the calculation of phase diagrams (CALPHAD) is being used to aid in the design of new alloys and optimize the welding processes to join them. By adopting the CALPHAD technique, all available thermochemical information both thermodynamic and phase equilibria data is used to fit model parameters used to describe the Gibbs energy of individual crystallographic phases. The Gibbs energy of each phase is described by an appropriate thermodynamic model dependent on its physical and chemical properties. Thermodynamic calculations can be made to predict properties such as liquidus and solidus temperatures and also the phases to form from the liquid during welding. DICTRA is a software package for accurate simulations of one-dimensional diffusion in multicomponent alloys. It can be used to investigate microsegregation effects during solidification taking into consideration cooling rates and time. These software tools can reduce the time and costs associated with trial-and-error experiments.

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