Carbon Effect on Thermal Ageing Simulations in Ferrite Steels

2012 ◽  
Vol 1444 ◽  
Author(s):  
Fabio Nouchy ◽  
Antoine Claisse ◽  
Pär Olsson
Keyword(s):  
Density Functional ◽  
Interatomic Potential ◽  
Kinetic Monte Carlo ◽  
Time Frame ◽  
Thermal Ageing ◽  
Computational Time ◽  
Carbide Formation ◽  
Monte Carlo Code ◽  
Functional Theory ◽  
Exponential Trend

ABSTRACTTwo major causes of hardening and subsequent embrittlement in ferrite steels are the spinodal decomposition of the binary Fe-Cr solid solution and the carbide formation due to the presence of carbon as foreign interstitial atoms. In the present work, simulations of the microstructure evolution due to thermal ageing are performed by means of a kinetic Monte Carlo code and using a state-of-the-art interatomic potential based on density functional theory (DFT) predictions and experimental data. The main issues concern the possibility to perform thermal ageing simulations in an acceptable computational time frame and to reproduce a realistic behavior of carbon kinetics and carbide formation. The simulations on the binary system show the microstructural evolution during thermal ageing and allowed to find an exponential trend related to the acceleration as a function of temperature. With the insertion of carbon in the model, the chromium precipitation tends to accelerate. The carbon clustering, analyzed separately, is faster with higher C concentrations and in lattices with segregated chromium.

Diffusion in Ni-Based Single Crystal Superalloys with Density Functional Theory and Kinetic Monte Carlo Method

2016 ◽  
Vol 20 (3) ◽  
pp. 603-618 ◽  
Author(s):  
Min Sun ◽  
Zi Li ◽  
Guo-Zhen Zhu ◽  
Wen-Qing Liu ◽  
Shao-Hua Liu ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Monte Carlo ◽  
Transition Rate ◽  
Density Functional ◽  
Diffusion Theory ◽  
Kinetic Monte Carlo ◽  
Functional Theory ◽  
Atom Diffusion ◽  
Time Stepping ◽  
Phase Intermetallic

AbstractIn the paper, we focus on atom diffusion behavior in Ni-based superalloys, which have important applications in the aero-industry. Specifically, the expressions of the key physical parameter – transition rate (jump rate) in the diffusion can be given from the diffusion theory in solids and the kinetic Monte Carlo (KMC) method, respectively. The transition rate controls the diffusion process and is directly related to the energy of vacancy formation and the energy of migration of atom from density functional theory (DFT). Moreover, from the KMC calculations, the diffusion coefficients for Ni and Al atoms in the γ phase (Ni matrix) and the γʹ phase (intermetallic compound Ni3Al) of the superalloy have been obtained. We propose a strategy of time stepping to deal with the multi-time scale issues. In addition, the influence of temperature and Al concentration on diffusion in dilute alloys is also reported.

Mechanisms of Diffusion and Dissociation of E-Centers in Silicon

2005 ◽  
Vol 237-240 ◽  
pp. 1129-1134
Author(s):  
Mariya G. Ganchenkova ◽  
V.A. Borodin ◽  
Risto M. Nieminen
Keyword(s):  
Density Functional Theory ◽  
Monte Carlo ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Density Functional ◽  
Kinetic Monte Carlo ◽  
Binding Energies ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Charge States

In this paper we discuss possible mechanisms of PV annealing in Si. Our approach includes a combination of density functional theory and lattice kinetic Monte-Carlo (LKMC) simulations. The density functional theory is used to find the binding energies and jump barriers for P-V pair at different separations (from one to three interatomic bonds between complex constituents) and in different charge states. The mobility of the complex is simulated by LKMC with event probabilities calculated based on the energies from ab-initio calculations. .

New Technique for AB Initio Atomistic Potentials and Application to Thermal Expansion of Ni/Cr Alloys

1992 ◽  
Vol 291 ◽  
Author(s):  
J. Mei ◽  
B.R. Cooper ◽  
Y.G. Hao ◽  
S.P. Lim ◽  
F.L. VanScoy
Keyword(s):  
Thermal Expansion ◽  
Ab Initio ◽  
Density Functional ◽  
Interatomic Potential ◽  
Coefficient Of Thermal Expansion ◽  
Many Body ◽  
Functional Theory ◽  
Transition Metal Alloys ◽  
Wide Range ◽  
Dynamics Simulations

ABSTRACTA scheme of developing ab initio many body potentials based on total energy calculations within density functional theory (DFT) is presented and demonstrated for transition metal alloys. An ab initio interatomic potential for Ni/Cr alloys is constructed with no input from experimental data. Molecular dynamics simulations have been performed to study thermal expansions. The coefficient of thermal expansion (CTE) has been calculated over a wide range of temperature, and good agreement is obtained between theory and experiment.

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