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中文核心期刊

面心立方夹层结构纳米多层金属的强化机制

ON THE STRENGTHENING MECHANISM OF NANOLAYERED METALS WITH FCC INTERLAYERS

  • 摘要: 纳米多层金属具备耐磨损、抗辐照损伤和超高强度等优异性能, 有望应用于航空、航天和核工业等领域的高端装备, 但受限于其强度与韧性的倒置关系, 无法满足极端服役环境对材料性能的需求. 近年来, 已有实验证实纳米多层金属的夹层结构设计是一种有效的强韧化策略, 但其强韧化机制因夹层结构的复杂性与多样性尚不清晰. 本研究采用分子动力学方法, 探究6种面心立方晶体夹层结构Cu/Ni纳米多层金属的压缩变形行为, 通过应力应变响应, 揭示不同夹层结构的强化效果差异, 基于位错形核过程, 阐明夹层特征参数对强度的影响机制, 最终提出强化设计方向. 结果表明, 在Cu/Ni纳米多层金属中引入Pd, Ag, Pt, Au, Pb与Al夹层均有强化作用, 且强化效果依次减弱. 夹层弹性模量对强度起主导作用, 降低夹层弹性模量会导致整体弹性模量与弹性应变减少, 降低材料强度. 低弹性模量夹层会承担额外弹性变形, 导致界面原子能量快速增长至位错形核阈值, 位错形核难度下降, 弹性应变减少. 界面原子势能分布表明, 位错线附近原子势能低于共格部分与层错部分. 增加晶格常数差异会提高界面位错密度, 界面能量因低能原子增加而降低, 位错形核所需能量增加, 弹性极限增加, 材料获得强化.

     

    Abstract: Nanolayered metals exhibit excellent properties such as wear resistance, radiation damage resistance, and ultra-high strength, which are highly anticipated for applications in high-end equipment in aerospace, aviation, and nuclear industries. However, they suffer from the trade-off between strength and toughness, failing to meet the requirements of the high-end equipment exposed to harsh environment. Existing experiments have confirmed that constructing nanolayered metals with interlayers is an effective strategy for strengthening and toughening nanolayered metals, but the complexity and diversity of interlayer structures have kept their strengthening and toughening mechanisms unclear. In this paper, molecular dynamics simulations are employed to investigate the compressive deformations of six Cu/Ni nanolayered metals with different face-centered cubic (FCC) crystal interlayers. The stress-strain responses show the differences in strengthening effects among these metals. Based on the dislocation nucleation process, the correlation between interlayer characteristic parameters and strength is established. A suggestion for strengthening nanolayered metals with interlayers is proposed. Simulation results show that introducing Pd, Ag, Pt, Au, Pb, and Al interlayers into Cu/Ni nanolayered metals enhances their strength, with the strengthening effect decreasing in the above order. The interlayer elastic modulus plays a dominant role in governing the strength of nanolayered metals. Interlayers with low elastic modulus tend to bear additional elastic deformation, which induces a rapidly increase in atomic energy at the interface. Dislocation nucleation is facilitated by the rapid energy accumulation, which reduces the elastic strain and consequently results in reduced strength. The energy distribution of interfaces reveals that the atomic potential energy of dislocation lines is lower than that of both the coherent region and the stacking fault region of the interface. An increase in the lattice constant difference enhances the interfacial dislocation density, reduces the initial interfacial energy due to more atoms with low energy at dislocation lines. The energy required for dislocation nucleation is enhanced, resulting in a larger elastic modulus, and strengthens the models.

     

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