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Phase Stability and Precipitation in L12-Strengthened CoCrNi Medium-Entropy Alloys at Intermediate Temperatures
Journal of Phase Equilibria and Diffusion ( IF 1.5 ) Pub Date : 2021-08-20 , DOI: 10.1007/s11669-021-00919-4
J. Y. C. Fang 1 , Z. B. Jiao 1 , W. H. Liu 2 , J. H. Luan 3
Affiliation  

Understanding phase stability and precipitation at intermediate temperatures is crucial for tailoring microstructures and mechanical properties of L12-strengthened multicomponent alloys. In this study, the precipitate type, morphology, and distribution of (CoCrNi)100−2x(AlTi)x (x = 3, 5, and 7 at.%) medium-entropy alloys (MEAs) at 600-900 °C were systematically investigated through a combination of scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, electron backscatter diffraction, and thermodynamic calculations. Our results reveal that the Al and Ti additions promote the destabilization of supersaturated fcc into L12 and σ phases, and the dominating phases of the MEAs change from fcc + L12 to fcc + L12 + σ and to L12 + σ + L21 phases as the Al and Ti concentrations increase. In addition, increasing the temperature leads to a change of precipitate morphology from lamellar to granular microstructures. The effects of alloying additions and aging temperature on the phase stability, precipitation behavior, and mechanical properties of the MEAs were discussed from the thermodynamic and kinetic points of view.



中文翻译:

L12 强化 CoCrNi 中熵合金在中温下的相稳定性和析出

了解中间温度下的相稳定性和析出对于调整 L1 2强化多组分合金的微观结构和机械性能至关重要。在本研究中,(CoCrNi) 100−2 x (AlTi) x (x = 3、5 和 7 at.%) 中熵合金 (MEA) 在 600-900 °C 下的沉淀类型、形态和分布通过扫描电子显微镜、能量色散 x 射线光谱、x 射线衍射、电子背散射衍射和热力学计算的组合进行系统研究。我们的结果表明,Al 和 Ti 的添加促进了过饱和 fcc 不稳定到 L1 2和 σ 相,并且随着 Al 和 Ti 浓度的增加,MEA 的主要相从 fcc + L1 2变为 fcc + L1 2  + σ 和 L1 2  + σ + L2 1相。此外,升高温度导致沉淀物形态从层状到粒状微观结构的变化。从热力学和动力学的角度讨论了合金添加和时效温度对 MEA 的相稳定性、析出行为和机械性能的影响。

更新日期:2021-08-20
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