目的 为在纳米尺度揭示纳米孪晶结构Alx(CoCrFeNi)1-x高熵合金的变形机理,探究铝含量、孪晶界间距及温度对其在纳米压痕过程中力学行为与微观结构演变的影响规律。方法 采用分子动力学模拟方法,构建具有不同孪晶界间距（0.61、1.84、3.08、4.31 nm）的纳米孪晶多晶Alx(CoCrFeNi)1-x模型（x=0.1、0.3、0.5）。在300~1 100 K的温度下进行纳米压痕模拟,并运用共同邻域分析、位错分析等方法,实时追踪位错形核、运动及其与晶界的交互作用。结果 晶体结构、孪晶界间距与铝含量均显著影响力学性能。在Al0.1成分下,单晶、普通多晶和纳米孪晶多晶的最大压痕力分别为489.21、340.60、375.41 nN,表明普通晶界引起软化,而纳米孪晶界能有效提升承载能力。当孪晶界间距为1.84 nm时,性能最优,最大加载力达411.04 nN,硬度为16.44 GPa,证实此为Hall-Petch强化与反Hall-Petch软化的临界间距。提高铝含量可进一步提升强度。结论 最优性能源于孪晶界对位错的有效阻碍与重排;高铝含量则加剧了晶格畸变,有效减小了层错能,促进层错形成与相变。温度升高通过热激活效应促进位错形核与运动,导致材料软化。铝含量、孪晶界间距与温度三者协同作用,共同调控着材料的强度与塑性。
Abstract
To reveal the deformation mechanisms of nanotwinned Alx(CoCrFeNi)1-x high-entropy alloys at the nanoscale, the work aims to investigate the effects of aluminum content, twin boundary spacing, and temperature on their mechanical behavior and microstructural evolution during nanoindentation. Molecular dynamics simulations were employed to construct nanotwinned polycrystalline Alx(CoCrFeNi)1-x models (x=0.1, 0.3, 0.5) with different twin boundary spacings (0.61, 1.84, 3.08, 4.31 nm). Nanoindentation simulations were conducted at temperatures ranging from 300 K to 1 100 K, and methods such as common neighbor analysis and dislocation analysis were used to track dislocation nucleation, motion, and their interactions with grain boundaries in real time. Crystal structure, twin boundary spacing, and aluminum content significantly affected the mechanical properties. For the Al0.1 composition, the maximum indentation forces for single crystal, conventional polycrystal, and nanotwinned polycrystal were 489.21, 340.60, and 375.41 nN, respectively, indicating that conventional grain boundaries caused softening, while nanotwin boundaries effectively enhanced load-bearing capacity. The optimal performance was achieved at a twin boundary spacing of 1.84 nm, with a maximum loading force of 411.04 nN and a hardness of 16.44 GPa, confirming this as the critical spacing for Hall-Petch strengthening and reverse Hall-Petch softening. Increasing aluminum content further improved strength. Optimal performance stems from the effective hindrance and rearrangement of dislocations by twin boundaries, while high aluminum content exacerbates lattice distortion, promoting stacking fault formation and phase transformation. Increasing aluminum content intensifies lattice distortion, promotes phase transformation, and enhances dislocation activity. Elevated temperatures facilitate dislocation nucleation and motion through thermal activation effects, leading to material softening. The synergistic effects of aluminum content, twin boundary spacing, and temperature collectively regulate the material's strength and plasticity.
关键词
高熵合金 /
纳米压印 /
分子动力学模拟 /
铝复合材料 /
纳米孪晶多晶
Key words
high-entropy alloys /
nanoindentation /
molecular dynamics /
composite aluminum /
nanotwined polycrystal
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基金
国家自然科学基金（52075342）; 深圳市自然科学基础研究（JCYJ20230808105224048）; 深圳市工业母机中小试基地（[2025]-59）
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