High-Temperature Oxidation Behaviors of AlCoCrFeNi2.1 and CoCrFeNiNb0.5 Eutectic High-Entropy Alloys: A Machine Learning-Assisted Design and Mechanism Study
摘要
Eutectic high-entropy alloys (EHEAs) show great potential as high-temperature structural materials; however, their oxidation resistance has not been sufficiently investigated. Conventional trial-and-error methods pose significant challenges for designing oxidation-resistant EHEAs. Notably, B2 and Laves phases are recognized for their excellent high-temperature oxidation resistance and readily form eutectic structures with the FCC phase. In this work, a machine learning (ML) framework was employed to screen for EHEAs with target FCC + B2 and FCC + Laves eutectic structures. Consequently, two representative EHEAs, AlCoCrFeNi2.1 (EH-Ni2.1) and CoCrFeNiNb0.5 (EH-Nb0.5), were designed and fabricated. Their isothermal oxidation behaviors at 1000 °C for up to 105 hours were systematically examined. Both alloys exhibited oxidation kinetics that followed a parabolic rate law. EH-Ni2.1 demonstrated superior oxidation resistance, with a specific mass gain of 1.82 mg/cm2 and a parabolic rate constant (Kp) of 0.03 mg2·cm−4·h−1. These values were significantly lower than those of EH-Nb0.5 (3.23 mg/cm2 and 0.1 mg2·cm−4·h−1, respectively). The oxide layer on EH-Nb0.5 consisted of an outer Cr2O3 layer and an inner layer containing CrNbO4, whereas EH-Ni2.1 formed a more protective oxide scale primarily composed of Al2O3 and Cr2O3. This study demonstrates the effectiveness of an ML-guided approach in developing oxidation-resistant EHEAs.