The reliable phase formation rule is demanded for high entropy alloys’ (HEAs) design and property regulation. Previous studies reveal the significant roles of thermodynamic and geometrical parameters in predicting phase structures of HEAs, whereas an accurate criterion is still not available. Herein, taking the most extensively studied Al‐containing HEAs as research object, two alloying parameters, i.e., d‐orbital energy level (Md) and bond order (Bo), combining with valence electron concentration (VEC) and atomic size difference (δ), are introduced to explore the phase stability of Al‐containing HEAs. The results indicate that single FCC solid solution tends to form in the range of δ below 4.5%, ordered phases (such as B2 and intermetallics) are more likely to be produced when the Md value of the alloy is beyond 1.06, and the FCC + BCC dual‐phase structures are mainly concentrated in the region of δ > 4.5% and Md < 1.06. The Md–δ criterion provides a reliable criterion of phase stability and a good guidance in alloy design for Al‐containing HEAs.

中文翻译：

---

含铝高熵合金相稳定性预测的新判据

高熵合金（HEA）的设计和性能调节需要可靠的相形成规则。先前的研究揭示了热力学参数和几何参数在预测HEA的相结构中的重要作用，但仍然没有准确的标准。在此，以研究最广泛的含Al HEA为研究对象，结合d价轨道电子能级（Md）和键序（Bo）两个化合参数，结合价电子浓度（VEC）和原子尺寸差（δ）引入）探索含铝HEA的相稳定性。结果表明，单一的FCC固溶体倾向于在δ范围内形成低于4.5％，当合金的Md值超过1.06时，更有可能产生有序相（例如B2和金属间化合物），并且FCC + BCC双相结构主要集中在δ  > 4.5％的区域并且Md <1.06。Md– δ准则提供了可靠的相稳定性准则，并为含铝HEA的合金设计提供了良好的指导。