Deformation mechanisms in crystalline-amorphous high-entropy composite multilayers
Deformation mechanisms in crystalline-amorphous high-entropy composite multilayers
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晶体-非晶高熵复合多层膜的变形机制
DOI：
10.1016/j.msea.2022.143144
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Misra, Amit
中科院分区：
文献类型：
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作者：
Jiang, Li;Bai, Zhitong;Powers, Max;Fan, Yue;Zhang, Wei;George, Easo P.;Misra, Amit
室温下磁控溅射用于合成具有标称成分 CrMnFeCoNi 和 TiZrNbHfTa 交替层的高熵复合多层 (HECM)。单层厚度为 50 nm 的 HECM 在 TiZrNbHfTa 层中呈现出非晶结构，在 CrMnFeCoNi 层中呈现出具有堆垛层错和纳米孪晶的面心立方 (FCC) 纳米晶结构。然而，单层厚度为 5 nm 的 HECM 在两层中都表现出完全非晶结构。纳米压痕，然后是压痕塑性区域的电子显微镜成像，用于通过实验表征硬度和变形能力。分子动力学模拟用于阐明变形机制。 5 nm 层厚的 HECM 具有 7.8 GPa 的高硬度，这归因于两层中的非晶结构以及凹痕周围的多个剪切带。 50 nm 层厚的 HECM 还表现出 5.6 GPa 的高硬度，但塑性分布更均匀，导致压痕周围的剪切带密度降低。 50 nm HECM 中的强化是 CoCrFeMnNi 中高密度堆垛层错和纳米孪晶以及 TiZrNbHfTa 层非晶结构的综合效应的结果。非晶态 50 nm TiZrNbHfTa 纳米层呈现出异质纳米玻璃型结构，其中非晶区的重新取向和团聚似乎为塑性流动提供了通道，从而增强了可变形性。高熵合金复合薄膜表现出各种精细结构，CrMnFeCoNi 中的纳米孪晶或均质非晶态，以及 TiZrNbHfTa 层中的异质非晶态，使得调整强度和变形能力的新方法成为可能。
Magnetron sputtering at room temperature was used to synthesize high-entropy composite multilayers (HECMs) with alternating layers of nominal composition CrMnFeCoNi and TiZrNbHfTa. HECMs with individual layer thickness of 50 nm exhibited an amorphous structure in the TiZrNbHfTa layers, and face-centered cubic (FCC) nanocrystalline structure with stacking faults and nanotwins in the CrMnFeCoNi layers. However, the HECMs with 5 nm individual layer thickness exhibited completely amorphous structures in both layers. Nanoindentation, followed by electron microscopy imaging of the indent plastic zone, was used to experimentally characterize the hardness and deformability. Molecular dynamics simulations were used to elucidate the deformation mechanisms. The high hardness of 7.8 GPa in the 5 nm layer thickness HECM is attributed to the amorphous structures in both layers with multiple shear bands around the indents. The 50 nm layer thickness HECM also exhibits high hardness of 5.6 GPa but with a more homogeneous spread of plasticity resulting in a reduced density of shear bands around indents. Strengthening in the 50 nm HECM results from a combined effect from the high density of stacking faults and nanotwins in CoCrFeMnNi, and the amorphous structure of the TiZrNbHfTa layers. The amorphous 50 nm TiZrNbHfTa nanolayers exhibit a heterogeneous nano-glass-type structure where the reorientation and agglomeration of amorphous zones seem to provide channels for plastic flow enabling enhanced deformability. Composite thin films of high entropy alloys exhibit a variety of fine structures, nanotwinned or homogeneous amorphous in CrMnFeCoNi, and heterogeneous amorphous in TiZrNbHfTa layers that enable new approaches to tune the strength and deformability.