Effect of Ni on Cu precipitation kinetics in \alpha-Fe by AKMC study

TL;DR

This study uses AKMC simulations to analyze how Ni affects Cu precipitation in Fe alloys, revealing Ni delays Cu clustering by reducing diffusion, with results aligning well with experimental data.

Contribution

It introduces a combined AKMC and time adjustment method to accurately model Cu precipitation kinetics and the influence of Ni in Fe-Cu-Ni alloys.

Findings

Ni causes a delay in Cu precipitation due to decreased diffusion coefficients.

Larger Cu clusters experience less diffusion reduction from Ni.

Ternary alloys show higher cluster density during coarsening, explained by reduced cluster mobility.

Abstract

The kinetics of coherent Cu rich precipitation in Fe-Cu and Fe-Cu-Ni alloys during thermal ageing have been modeled by Atomic Kinetic Monte Carlo method (AKMC). The AKMC is parameterized by existing ab-inito data to treat vacancy mediated diffusion which is depend on local atomic environment. A nonlinear semi-empirical time adjusting method is proposed to rescaled the MC time. The combining AKMC and time adjusting method give a good agreement with experiments and other simulations, including advancement factor and the Cu cluster mobility. Simulations of ternary alloys reveal Ni has a temporal delay effect on Cu precipitation. This effect is caused by the decreasing of diffusion coefficient of Cu clusters. And the reduction effect of diffusion coefficient weakens with larger Cu cluster size. The simulation results can be used to explain the experimental phenomenon that ternary Fe-Cu-Ni alloys have higher cluster number density than corresponding binary during coarsening stage, which is related to cluster mobility.