Kinetics of heterogeneous grain boundary precipitation of Ni3Al in nickel alloy

Abstract

We study heterogeneous precipitation of Ni3Al in nickel alloy using Monte Carlo simulations based on a simple atomic description of the main mechanisms, which control the kinetic pathway at the grain boundary and in the bulk. A complete model of the grain boundary takes into account both the Σ5 [0 0 1](2 1 0) tilt grain boundary structure and the misorientation between the two grains. The simulation involves realistic vacancy diffusion mechanisms, with a faster diffusion of substitutional atoms at the grain boundary and slower diffusion in the bulk. The grain boundary interacts with solute atoms through local segregation energies. The system was parametrized from experimental data such as cohesive energy, solubility limit and diffusion coefficients. The segregation energies have been computed using a relaxed equilibrium Monte Carlo method based on the Metropolis et al algorithm in conjunction with the embedded atom method potentials. Owing to the complexity of this problem, we first present the Ni3Al homogeneous and heterogeneous precipitation kinetics and then we explore the impact of pair interaction energies at grain boundaries on the morphology of precipitates, as well as the impact of segregation energies on the nucleation behaviour.