We propose Monte Carlo simulations of the NbC grain boundary (GB) precipitation kinetics in a-iron, based on an atomic description of the main mechanisms that control the kinetic pathway. The simulation involves realistic diffusion mechanisms, with a rapid diffusion of C atoms by interstitial jumps and a slower diffusion of Fe and Nb atoms by vacancy jumps; a simple model of the GB which reproduces the equilibrium segregation properties of Nb and C; and a point defect source which drives the vacancy concentration towards its equilibrium value. Depending on the precipitation conditions, Monte Carlo simulations predict different kinetic behaviours, including early segregation of C atoms at the grain boundaries, transient precipitation of metastable carbides, and homogeneous and heterogeneous NbC precipitation.
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机译:基于对控制动力学途径的主要机制的原子描述,我们提出了对a-iron中NbC晶界(GB)析出动力学的蒙特卡罗模拟。模拟涉及真实的扩散机制,C原子通过间隙跳跃快速扩散,Fe和Nb原子通过空位跳跃扩散较慢;GB的简单模型,再现了Nb和C的平衡偏析性质;以及驱动空位浓度趋近其平衡值的点缺陷源。根据析出条件,蒙特卡罗模拟预测了不同的动力学行为,包括晶界处 C 原子的早期偏析、亚稳态碳化物的瞬时析出以及均匀和非均相 NbC 沉淀。
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