Strengthening in multi-principal element alloys with local-chemical-order roughened dislocation pathways
Strengthening in multi-principal element alloys with local-chemical-order roughened dislocation pathways
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DOI：
10.1038/s41467-019-11464-7
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发表时间：
2019-08-08
影响因子：
16.6
通讯作者：
Ma, Evan
中科院分区：
文献类型：
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作者：
Li, Qing-Jie;Sheng, Howard;Ma, Evan
高熵合金和中熵合金被假定具有与多种元素近乎等比例的理想混合固溶体（SS）一样高的构象熵。然而，除了在非常高的温度下，焓相互作用不可避免地使得这种化学无序的固溶体罕见且亚稳。在此，我们强调各种各样的局域化学有序（LCO），它使这些浓缩固溶体有别于传统的溶剂 - 溶质固溶体。通过原子模拟，我们揭示了多主元NiCoCr固溶体的局域化学有序随合金加工条件而变化，产生了广泛的广义层错能。我们表明局域化学有序增加了能量景观的崎岖度，并提高了控制位错活动的激活能垒。这影响了滑移、层错和孪晶中位错路径的选择，并通过纳米尺度的位错段脱钉机制增加了位错运动的晶格摩擦力。相反，剧烈塑性变形使局域化学有序朝着随机固溶体的方向降低。
High-entropy and medium-entropy alloys are presumed to have a configurational entropy as high as that of an ideally mixed solid solution (SS) of multiple elements in near-equal proportions. However, enthalpic interactions inevitably render such chemically disordered SSs rare and metastable, except at very high temperatures. Here we highlight the wide variety of local chemical ordering (LCO) that sets these concentrated SSs apart from traditional solvent-solute ones. Using atomistic simulations, we reveal that the LCO of the multiprincipal-element NiCoCr SS changes with alloy processing conditions, producing a wide range of generalized planar fault energies. We show that the LCO heightens the ruggedness of the energy landscape and raises activation barriers governing dislocation activities. This influences the selection of dislocation pathways in slip, faulting, and twinning, and increases the lattice friction to dislocation motion via a nanoscale segment detrapping mechanism. In contrast, severe plastic deformation reduces the LCO towards random SS.