NiCoCr高熵合金中Cr含量对其变形行为影响的原位透射电镜研究

NiCoCr高熵合金中Cr含量对其变形行为影响的原位透射电镜研究

陈思静，余  倩

（浙江大学材料科学与工程学院，硅材料国家重点实验室，电子显微镜中心，浙江 杭州310027）

摘  要 本文采用透射电镜中的原位拉伸实验和X射线衍射，研究对比了高熵合金NiCoCr增加了1.1%Cr含量前后的微观结构与变形机理的不同，以探究元素含量对于高熵合金力学性能的影响。分析得出1.1%Cr含量的增加不会引起第二相的出现，但是会增大晶面间距。与NiCoCr类似，Ni_32.8Co_32.8Cr_34.4中观察到大量的不全位错运动以及孪晶，它们的协同作用为材料提供了良好的强塑性。不同的是，在Ni_32.8Co_32.8Cr_34.4中，波纹状位错形貌更为显著，且分段式分解成不全位错，滑移相对困难。在变形后期，Ni_32.8Co_32.8Cr_34.4中出现了大量位错的交滑移。除此之外还观察到，Ni_32.8Co_32.8Cr_34.4中的全位错更易分解，扩展位错的扩展宽度更宽，增大了层错相交的机会，可能对材料强塑性提高有重要贡献。这些现象都说明，仅仅少量元素含量的变化即会在高熵合金中产生位错滑移阻力以及局部层错能的影响。

关键词：高熵合金；Cr含量；原位拉伸；位错行为； 层错能

中图分类号：TG115.21⁺5.3 

文献标识码：Adoi:10.3969/j.issn.1000-6281.2020.06.002

In situ TEM investigation on the influence of Cr content in NiCoCr high-entropy alloy on the deformation mechanism

CHEN Si-jing，YU Qian *

( Center of Electron Microscopy，State Key Laboratory of Silicon Materials，School of Material Science and Engineering，Zhejiang University, Hangzhou Zhejiang 310027，China)

Abstract  In this paper, the in-situ tensile experiments in transmission electron microscope and X-ray diffraction analysis were performed to study and compare the microstructure and deformation mechanism of high-entropy alloy NiCoCr before and after increment of 1.1% Cr content.For the purpose of examing the influence of Cr content on the microstructure and mechanical properties of NiCoCr. The analysis shows that the 1.1% increase of  Cr content will not result in the formation of the second phase, but will increase the interplanar spacing. Similar to NiCoCr, a large number of partial dislocations and twins were observed in Ni_32.8Co_32.8Cr_34.4. Their synergistic effect provides the material with decent strength and plasticity. The difference is that in Ni_32.8Co_32.8Cr_34.4, the dislocation morphology is more tortuous, and the dislocation is unevenly dissociated. Therefore, it is relatively difficult for the dislocation to move. Besides, the occurrence of cross-slip was also found at the later stage of deformation. In addition, it was observed that the full dislocations in Ni_32.8Co_32.8Cr_34.4 are easier to dissociate, and the expansion width of extended dislocation is also wider, which increases the chances of stacking faults intersection and may contribute to the strength and ductility. These phenomena suggest that even small adjustment of element content may significantly influence the obstacle effect of the matrix on dislocation motion and local stacking fault energy state.

Keywords   high-entropy alloy；Cr content；in-situ tensile test；dislocation behavior；stacking-fault energy

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