Abstract
The performance of modern Ni-based superalloys depends critically on the kinetic transport of point defects around solutes such as rhenium. Here, we use atomistic calculations to study the diffusion of vacancy in the low-concentration limit, using the crystalline fcc-framework nickel as a model. On-the-fly kinetic Monte Carlo is combined with an efficient energy-valley search to find energies of saddle points, based on energetics from the embedded atom method. With this technique, we compute the local energy barriers to vacancy hopping, tracer diffusivities, and migration energies of the low-concentration limit of Ni-Re alloys. It was estimated that the computed diffusion rates are comparable to the reported rates. The presence of Re atoms affects the difference between the energy of the saddle point and the initial energy of point defect hopping. In pure Ni, this difference is about 1 eV, while at 9.66 mol% Re, the value is raised to about 1.5 eV. The vacancy migration energy of vacancy in the 9.66 mol % Re sample is raised above that of pure Ni. Our findings demonstrate that even in the low-concentration limit, Re solute atoms continue to play a crucial role in the mobility of the vacancies.
Highlights
Ni-based superalloys are known to exhibit remarkable mechanical properties influenced by the interplay between dislocations and alloying elements [1, 2]
Such studies require inputs of atomistic details on the defect interaction mechanism [20], which in turn limits their predictive capability and prevents a faithful understanding of the microstructural evolution and microchemistry, including those of the Re effects. To overcome this timescale issue, many modern dynamic calculations rely on the concepts of all-atom activation/relaxation techniques based on the concepts of escaping from free-energy minima or metadynamics introduced by Laio and Parrinello [21]. is calculation approach assumes no particular atomistic trajectory in the system evolution, but a few activation parameters
Atomistic calculations based on an activated saddle point search method, namely, the autonomous basin climbing (ABC) method, was utilized to study the diffusion of vacancy in the low-concentration limit. e energetic terms are obtained through an embedded atom potential, while the material kinetic was represented by the kinetic Monte Carlo process
Summary
Nuttapong La-ongtup ,1 Suttipong Wannapaiboon ,2 Piyanut Pinyou ,3 Worawat Wattanathana ,1 and Yuranan Hanlumyuang 1. On-the-fly kinetic Monte Carlo is combined with an efficient energy-valley search to find energies of saddle points, based on energetics from the embedded atom method. With this technique, we compute the local energy barriers to vacancy hopping, tracer diffusivities, and migration energies of the low-concentration limit of Ni-Re alloys. In pure Ni, this difference is about 1 eV, while at 9.66 mol% Re, the value is raised to about 1.5 eV. E vacancy migration energy of vacancy in the 9.66 mol % Re sample is raised above that of pure Ni. Our findings demonstrate that even in the low-concentration limit, Re solute atoms continue to play a crucial role in the mobility of the vacancies
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