Abstract
In this study, we investigated the precipitation with characteristic shape in the microstructure during post-implantation annealing via a theoretical modeling approach. The processes of precipitates formation and evolution during phase separation were based on a nucleation and growth mechanism of atomic diffusion. Different stages of the precipitation, including the nucleation, growth and coalescence, were distinctly revealed in the numerical simulations. In addition, the influences of ion dose, temperature and crystallographic symmetry on the processes of faceted precipitation were also demonstrated. To comprehend the kinetic mechanism, the simulation results were further analyzed quantitatively by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. The Avrami exponents obtained from the regression curves varied from 1.47 to 0.52 for different conditions. With the increase of ion dose and temperature, the nucleation and growth of precipitations were expedited in accordance with the shortened incubation time and the raised coefficient of growth rate. A miscellaneous shape of precipitates in various crystallographic symmetry systems could be simulated through this anisotropic model. From the analyses of the kinetics, more fundamental information about the nucleation and growth mechanism of faceted precipitation during post-implantation annealing was acquired for future application.
Highlights
In the field of materials science and engineering, the knowledge of phase transformation always attracts great attention, especially for phase separation or precipitation
Regarding to the fundamental principle, the phenomenon of phase separation is involved with the atomic diffusion and the kinetics mechanism of nucleation and growth during processing, which dictates the properties of materials, e.g. the mechanical strength and electric conductivity
According to the theory of phase transformation,[23] the incubation time during nucleation is principally controlled by the level of supersaturation and the interfacial energy between the matrix and precipitates, which are newly created in this period
Summary
In the field of materials science and engineering, the knowledge of phase transformation always attracts great attention, especially for phase separation or precipitation. The quantitative analyses with KolmogorovJohnson-Mehl-Avrami (KJMA) equation for different conditions were applied to demonstrate the influences of the implantation parameters, such as the ion dose, temperature, and crystallographic symmetry, on the formation and evolution of precipitates. This theoretical model for structural evolution of phase separation reveals the underlying physical mechanism of nucleation and growth of faceted precipitation, which provides a helpful guidance for the fabrication design and procedure control in the techniques of ion implantation with subsequent thermal-annealing
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