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Type Soisson, F.; Barbu, A.; Martin, G.
  Publication Monte Carlo simulations of copper precipitation in dilute iron-copper alloys during thermal ageing and under electron irradiation Volume Journal Article
Pages 1996
  Abstract Acta Materialia  
  Corporate Author Acta Mater.  
Publisher 44  
Editor 9
  Summary Language 3789-3800 Series Editor  
Abbreviated Series Title We propose a Monte Carlo simulation of the coherent precipitation of copper in α-iron using a vacancy diffusion mechanism. The only adjustable parameters are the vacancy concentration and the local vacancy jump frequencies. The latter are deduced from pair interactions restricted to nearest neighbour atoms. Precipitation kinetics are compared to recent experimental studies of precipitation in dilute Fe---Cu solid solutions during thermal ageing or electron irradiation (electrical resistivity measurements). The degree of advancement of the unmixing process as a function of time has the form of a stretched exponential, in good agreement with experiment. The simulation also provides interesting information on precipitate morphology and growth mechanisms which are useful for experimental data analysis.
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no NU @ karnesky @ 1917
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Mao, Zugang; Sudbrack, Chantal K.; Yoon, Kevin E.; Martin, Georges; Seidman, David N. The mechanism of morphogenesis in a phase separating concentrated multi-component alloy Journal Article 2007 Nature Materials 6 3 210-216 What determines the morphology of a decomposing alloy? Besides the well established effect of the nucleation barrier, we demonstrate that, in a concentrated multi-component Ni(Al,Cr) alloy, the details of the diffusion mechanism affect strongly the kinetic pathway of precipitation. Our argument is based on the combined use of atomic-scale observations, employing 3-dimensional atom-probe tomography (3-D APT), lattice kinetic Monte Carlo simulations, and the theory of diffusion. By an optimized choice of thermodynamic and kinetic parameters we first reproduce the 3-D APT observations, in particular the early stage transient occurrence of coagulated precipitates. We then modify the kinetic correlations among the atomic fluxes in the simulation, without altering the thermodynamic driving force for phase separation, by changing the vacancy-solute interactions, resulting in a suppression of coagulation. Such changes can only be quantitatively accounted for with nonzero values for the off-diagonal terms of the Onsager matrix, at variance with classical models. no NU @ karnesky @ 1885
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Martin, G. Reconciling the Classical Nucleation Theory and Atomic Scale Observations and Modeling Journal Article 2006 Advanced Engineering Materials 8 12 1231-1236 Cast iron Fatigue Graphite No abstract. 1527-2648 no NU @ karnesky @ Martin2006 1859
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Clouet, E.; Nastar, M.; Barbu, A.; Sigli, C.; Martin, G. An Atomic and Mesoscopic Study of Precipitation Kinetics in Al-Zr-Sc Alloys Journal Article 2006 Advanced Engineering Materials 8 12 1228-1231 Aluminum alloys Kinetics Precipitation No abstract. 1527-2648 no NU @ karnesky @ E.Clouet2006 1856
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Martin, G. The Joint Research Program ?CPR Precipitation?: - Breakthroughs in the Understanding of Kinetic Pathways for the Early Stages of Phase Separation Journal Article 2006 Advanced Engineering Materials The Joint Research Program ?CPR Precipitation? 8 12 1222-1224 No abstract. 1527-2648 no NU @ karnesky @ Martin2006 1854
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Blavette, D.; Soisson, F.; Martin, G.; Pareige, C. Ordering and Phase Separation in Model Superalloys: 3D Atom Probe versus Monte Carlo simulation Book Chapter 1999 Proceedings of the International Conference on Solid-Solid Phase Transformations 65-72 ordering, phase separation, Ni-Al-Cr, 3D atom-probe, monte carlo simulation; 3D Atom Probe, Superalloys The kinetics of ordering and unmixing in model superalloys (NiCrAl) at 600C were effects in the ' investigated at the atomic scale using 3D atom probe and by transmission electron it ion here that microscopy. Very fine precipitates (lnm) with a well ordered structure (Ni3 Al) were observed in the early stages of growth At this stage, their composition was found very close to the equilibrium composition of the y' phase. Coarsening of y' precipitates was observed in the early stages, for particle radius under 2 nm Monte Carlo simulations of kinetics based on a atom-vacancy exchanges mechanism and using a residence time algorithm were also conducted. Experiments and simulations have shown a good agreement. Monte carlo simulations indicate that short range ordering of both Al and Cr precedes the nucleation and Ni3AI ordered phase. The Cr content in nuclei was foun: to be close to that of solution in the very early stages of phase separation no NU @ karnesky @ 275
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Clouet, Emmanuel; Barbu, Alain; La, Ludovic; Martin, Georges Precipitation kinetics of Al3Zr and Al3Sc in aluminum alloys modeled with cluster dynamics Journal Article 2005 Acta Materialia Acta Mater. 53 8 2313-2325 Precipitation; Kinetics; Aluminum alloys; Cluster dynamics Precipitation kinetics of Al3Zr and Al3Sc in aluminum supersaturated solid solutions is studied using cluster dynamics, a mesoscopic modeling technique which describes the various stages of homogeneous precipitation by a single set of rate equations. The only parameters needed are the interface free energy and the diffusion coefficient which are deduced from an atomic model previously developed to study the same alloys. A comparison with kinetic Monte-Carlo simulations based on the vacancy diffusion mechanism shows that cluster dynamics correctly predicts the precipitation kinetics provided a size dependent interface free energy is used. It also manages to reproduce reasonably well existing experimental data. no NU @ karnesky @ 211
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Brechet, Yves; Martin, Georges Nucleation problems in metallurgy of the solid state: recent developments and open questions Journal Article 2006 Comptes Rendus Physique 7 9-10 959-976 Coherent precipitation; Recrystallisation; Precipitation coherente; Recristallisation Nucleation processes play a key role in the microstructure evolution of metallic alloys during thermomechanical treatments. These processes can involve phase transformations (such as precipitation) and structural instabilities (such as recrystallisation). Although the word `nucleation' is used in both cases, the situation is profoundly different for precipitation and for recrystallisation on which this article is focussed. In the case of precipitation, species are conserved and the underlying physics is stochastic fluctuations, allowing the apparition of critical germs of the new phase. In the case of recrystallisation, the underlying physical phenomenon is the progressive growth of subgrain structures leading to an unstable configuration, allowing a dislocation free grain to grow at the expense of a dislocated one. The two cases require different types of modelling which are presented in the article. To cite this article: Y. Brechet, G. Martin, C. R. Physique 7 (2006). no NU @ karnesky @ 9593
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Martin, G. A diffuse interface model for the interfacial transfer coefficient Journal Article 2005 Acta Materialia 53 9 2629-2632 Diffusion; Interfaces; Alloys; Kinetics; Phase field models; Theory Based on an extension to non-equilibrium problems, of Cahn's interface layer thermodynamics, we demonstrate that the matrix of transfer coefficients across a coherent interface between two phases, [alpha] and [beta], can be viewed as a correction to the Onsager's matrix of mobility coefficients along the continuous concentration profile. The latter coefficients are defined along the equilibrium concentration profile in the interfacial layer and in the [alpha]- and [beta]-phases. Combining the above definition with that of solute interfacial excess, we can define transfer coefficients relative to two components chosen arbitrarily, the values of which are intrinsic properties of the interfacial layer, independent of its precise location and thickness. no NU @ p-kolli @ 9702
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Wu, Ling-Mei; Seyring, Martin; Rettenmayr, Markus; Wang, Wen-Hsiung Characterization of precipitate evolution in an artificially aged Al-Zn-Mg-Sc-Zr alloy Journal Article 2010 Materials Science and Engineering: A 527 1068-1073 Al-Zn-Mg-Sc-Zr alloy; age hardening; precipitation; transmission electron microscopy (TEM) The precipitates of an age hardenable Al-Zn-Mg-Sc-Zr alloy aged at 140 °C have been studied by transmission electron microscopy (TEM). The results are interpreted in terms of structural transformations that involve two types of Guinier-Preston (GP) zones (I and II), the metastable [eta]â hardening precipitate and the stable phase [eta]-phase (MgZn2). At early stages of ageing, the GPI zones act as nucleation sites for the plate-like [eta]â phase which precipitates on the 111Al plane. The transformation from [eta]â to [eta] occurs gradually at longer ageing times. The [eta] particles mainly consist of [eta]1 and [eta]2 phase, with small amounts of [eta]4 type and minor quantities of [eta]â type structures. Furthermore, while a fine dispersion of coherent Al3(Sc,Zr) precipitates is known to have a beneficial effect on the strengthening of the alloy, the formation of GPII zones is suppressed in the presence of zirconium that leads to a reduction in the amount of [eta]â formed during subsequent ageing. 0921-5093 no NU @ karnesky @ Wu2009 10688
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