Chen Yuan, Ren Siwei, Liu Xiubo, Peng Jing, Liaw Peter K
Hunan Province Key Laboratory of Materials Surface/Interface Science Technology, Central South University of Forestry Technology, Changsha 410004, China.
College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, China.
Materials (Basel). 2024 Jul 25;17(15):3689. doi: 10.3390/ma17153689.
Amorphous/crystalline high-entropy-alloy (HEA) composites show great promise as structural materials due to their exceptional mechanical properties. However, there is still a lack of understanding of the dynamic nanoindentation response of HEA composites at the atomic scale. Here, the mechanical behavior of amorphous/crystalline HEA composites under nanoindentation is investigated through a large-scale molecular dynamics simulation and a dislocation-based strength model, in terms of the indentation force, microstructural evolution, stress distribution, shear strain distribution, and surface topography. The results show that the uneven distribution of elements within the crystal leads to a strong heterogeneity of the surface tension during elastic deformation. The severe mismatch of the amorphous/crystalline interface combined with the rapid accumulation of elastic deformation energy causes a significant number of dislocation-based plastic deformation behaviors. The presence of surrounding dislocations inhibits the free slip of dislocations below the indenter, while the amorphous layer prevents the movement or disappearance of dislocations towards the substrate. A thin amorphous layer leads to great indentation force, and causes inconsistent stacking and movement patterns of surface atoms, resulting in local bulges and depressions at the macroscopic level. The increasing thickness of the amorphous layer hinders the extension of shear bands towards the lower part of the substrate. These findings shed light on the mechanical properties of amorphous/crystalline HEA composites and offer insights for the design of high-performance materials.
非晶态/晶态高熵合金（HEA）复合材料因其优异的力学性能而作为结构材料展现出巨大潜力。然而，目前仍缺乏对HEA复合材料在原子尺度下动态纳米压痕响应的理解。在此，通过大规模分子动力学模拟和基于位错的强度模型，从压痕力、微观结构演变、应力分布、剪切应变分布和表面形貌等方面研究了非晶态/晶态HEA复合材料在纳米压痕下的力学行为。结果表明，晶体内元素的不均匀分布导致弹性变形过程中表面张力的强烈不均匀性。非晶态/晶态界面的严重失配与弹性变形能量的快速积累导致大量基于位错的塑性变形行为。周围位错的存在抑制了压头下方位错的自由滑移，而非晶层则阻止了位错向基体的移动或消失。薄的非晶层导致较大的压痕力，并导致表面原子的堆积和运动模式不一致，从而在宏观层面上产生局部凸起和凹陷。非晶层厚度的增加阻碍了剪切带向下延伸至基体下部。这些发现揭示了非晶态/晶态HEA复合材料的力学性能，并为高性能材料的设计提供了见解。
