Achieving a High-Strength CoCrFeNiCu High-Entropy Alloy with an Ultrafine-Grained Structure via Friction Stir Processing
Achieving a High-Strength CoCrFeNiCu High-Entropy Alloy with an Ultrafine-Grained Structure via Friction Stir Processing
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DOI：
10.1007/s40195-020-01037-9
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发表时间：
2020-04
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影响因子：
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通讯作者：
Ning Li;C. Jia;Zhiwen Wang;Lihui Wu;D. Ni;Zheng-Kun Li;H. Fu;P. Xue;B. Xiao;Zongqing Ma;Y. Shao;Yunpeng Chang
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文献类型：
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作者：
Ning Li;C. Jia;Zhiwen Wang;Lihui Wu;D. Ni;Zheng-Kun Li;H. Fu;P. Xue;B. Xiao;Zongqing Ma;Y. Shao;Yunpeng Chang
摘要高熵合金是一类具有潜在工程应用价值的新型材料，但如何获得超细或纳米晶结构的高熵合金一直是一个挑战。在这里，我们首先提出了一个等原子的CoCrFeNiCu HEA具有优异的机械性能，通过摩擦搅拌处理（FSP）。铸造CoCrFeNiCu HEA中Cu元素的偏析几乎被消除，铸造CoCrFeNiCu HEA中粗大的两相组织（几个微米）转变为超细晶单相组织（150 nm），其中含有大量的大角度晶界和纳米级形变孪晶。这种独特的微观结构主要归因于FSP过程中剧烈的塑性变形，以及动力学上的迟滞扩散效应和晶体学上的晶格畸变效应。FSP显著提高了CoCrFeNiCu HEA的硬度和屈服强度，硬度和屈服强度分别达到380 HV和1150 MPa以上，是基体材料的1.5倍以上。FSP强化的主要原因是晶粒明显细化，并伴随着较大的晶格畸变和纳米孪晶。本研究为大幅度细化铸造CoCrFeNiCu热电致变色材料的组织和提高其强度提供了一种新的方法。
AbstractHigh-entropy alloys (HEAs) are a new class of materials with a potential engineering application, but how to obtain ultrafine or nano-sized crystal structures of HEAs has been a challenge. Here, we first presented an equiatomic CoCrFeNiCu HEA with excellent mechanical properties obtained via friction stir processing (FSP). After FSP, the Cu element segregation in the cast CoCrFeNiCu HEA was almost eliminated, and the cast coarse two-phase structure (several micrometers) was changed into an ultrafine-grained single-phase structure (150 nm) with a large fraction of high-angle grain boundaries and nanoscale deformation twins. This unique microstructure was mainly attributed to the severe plastic deformation during FSP, and the sluggish diffusion effect in dynamics and the lattice distortion effect in crystallography for HEAs. Furthermore, FSP largely improved the hardness and yield strength of the CoCrFeNiCu HEA with a value of 380 HV and more than 1150 MPa, respectively, which were > 1.5 times higher than those of the base material. The great strengthening after FSP was mainly attributed to the significant grain refinement with large lattice distortion and nano-twins. This study provides a new method to largely refine the microstructure and improve the strength of cast CoCrFeNiCu HEAs.Graphic Abstract