梯度Al0.1CoCrFeNi多主元合金最佳强-塑协同的晶粒尺寸分布分子动力学模拟

Molecular Dynamics Simulation of Grain-Size Range for Optimal Strength-Ductility Synergy in Gradient Nano-Grained Al0.1CoCrFeNi High-Entropy Alloy

摘要:

在金属材料中引入梯度纳米（gradient nano-grained，GNG）结构，可以弱化或消除强度和塑性的倒置关系，而梯度晶粒尺寸的分布对调控强度和塑性的协同优化具有重要作用。本工作采用分子动力学模拟方法，系统研究了梯度晶粒尺寸分布对GNG Al_0.1CoCrFeNi多主元合金力学特性、应变和应变分布、位错分布以及晶界运动等影响。结果表明，当梯度晶粒尺寸区间位于反霍尔-佩奇关系（inverse Hall-Petch，IHP）→霍尔-佩奇关系（Hall-Petch，HP）过渡区（9.6~19.2 nm）时，体系呈现最佳的强度与塑性协同提高。进一步分析表明，当梯度晶粒尺寸区间处于IHP→HP过渡区（9.6~19.2 nm）时，体系内局域应变和应力的梯度最为显著，而且此时位错密度最大，从而引起了强度与塑性的最佳匹配。当梯度晶粒尺寸区间处于IHP软化区时，晶界活动对塑性变形起主导地位；处于HP强化区时，位错滑移成为塑性变形的主要形式。

Abstract:

The introduction of gradient nano-grained (GNG) structure into metallic materials is recognized as an effective strategy to mitigate or eliminate the strength-ductility trade-off. The distribution of grain sizes within the gradient structure plays a critical role in modulating the strength-ductility synergy. In this study, the influences of the gradient grain-size distribution on the mechanical characteristics, strain and strain distributions, dislocation distribution, and grain boundary migration were investigated using molecular dynamics simulations. The results demonstrate that an optimal strength-ductility synergy is achieved when the gradient grain-size range lies within the transition region between the inverse Hall-Petch (IHP) and Hall-Petch (HP) regimes (9.6?19.2 nm). Further analysis indicates that within the IHP-HP transition zone (9.6?19.2 nm), the gradients of local strain and stress are the most pronounced, and the dislocation density reaches a maximum, leading to an optimal balance between strength and ductility. When the gradient grain-size range falls within the IHP softening regime, the plastic deformation is predominantly governed by grain boundary-mediated mechanisms. In contrast, when the gradient grain-size range is located in the HP strengthening regime, dislocation slip becomes the primary mode of plastic deformation.