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.

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。