Tuning element distribution, structure and properties by composition in high-entropy alloys
Tuning element distribution, structure and properties by composition in high-entropy alloys
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通过高熵合金成分调整元素分布、结构和性能
DOI：
10.1038/s41586-019-1617-1
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发表时间：
2019-10-10
期刊：
影响因子：
64.8
通讯作者：
Yu, Qian
中科院分区：
文献类型：
--
作者：
Ding, Qingqing;Zhang, Yin;Yu, Qian
高熵合金是一类含有五种或五种以上接近等原子比例的元素的材料（1，2）。它们的非常规成分和化学结构有望实现前所未有的机械性能组合（3-8）。这种合金的合理设计取决于对近乎无限组成空间中的组成-结构-性质关系的理解（9，10）。在这里，我们使用原子分辨率的化学映射来揭示广泛研究的面心立方CrMnFeCoNi Cantor合金（2）和一种新的面心立方合金CrFeCoNiPd的元素分布。在Cantor合金中，五种组成元素的分布相对随机和均匀。相比之下，在CrFeCoNiPd合金中，钯原子的原子大小和电负性与其他元素明显不同，均匀性大大降低;所有五种元素都倾向于显示出更大的聚集，初始浓度波的波长（11，12）小至1至3纳米。由此产生的纳米级交替拉伸和压缩应变场导致相当大的阻力位错滑移。在应变实验过程中的原位透射电子显微镜揭示了大量的位错交滑移从塑性变形的早期阶段，导致多个滑移系统之间的强烈的位错相互作用。这些变形机制中的CrFeCoNiPd合金，这显着不同于那些在康托合金和其他面心立方高熵合金，促进了显着的波动成分和堆垛层错能的增加，导致更高的屈服强度，而不损害应变硬化和拉伸韧性。绘制原子尺度的元素分布为理解化学结构提供了机会，从而为调整成分和原子构型以获得出色的机械性能提供了基础。
High-entropy alloys are a class of materials that contain five or more elements in near-equiatomic proportions(1,2). Their unconventional compositions and chemical structures hold promise for achieving unprecedented combinations of mechanical properties(3-8). Rational design of such alloys hinges on an understanding of the composition-structure-property relationships in a near-infinite compositional space(9,10). Here we use atomic-resolution chemical mapping to reveal the element distribution of the widely studied face-centred cubic CrMnFeCoNi Cantor alloy(2) and of a new face-centred cubic alloy, CrFeCoNiPd. In the Cantor alloy, the distribution of the five constituent elements is relatively random and uniform. By contrast, in the CrFeCoNiPd alloy, in which the palladium atoms have a markedly different atomic size and electronegativity from the other elements, the homogeneity decreases considerably; all five elements tend to show greater aggregation, with a wavelength of incipient concentration waves(11,12) as small as 1 to 3 nanometres. The resulting nanoscale alternating tensile and compressive strain fields lead to considerable resistance to dislocation glide. In situ transmission electron microscopy during straining experiments reveals massive dislocation cross-slip from the early stage of plastic deformation, resulting in strong dislocation interactions between multiple slip systems. These deformation mechanisms in the CrFeCoNiPd alloy, which differ markedly from those in the Cantor alloy and other face-centred cubic high-entropy alloys, are promoted by pronounced fluctuations in composition and an increase in stacking-fault energy, leading to higher yield strength without compromising strain hardening and tensile ductility. Mapping atomic-scale element distributions opens opportunities for understanding chemical structures and thus providing a basis for tuning composition and atomic configurations to obtain outstanding mechanical properties.