Superior oxidation behavior, good electrical conductivity, and thermophysical properties of FeCr_1.2Ni_1.5Al multi-principal element alloys

Despite the FeCr_1.2Ni_xAl multi-principal element alloys (MPEAs) have been demonstrated to possess superior mechanical properties, a fundamental understanding of their thermophysical properties and high-temperature oxidation mechanisms is deficient. Hence, the objective of this study was to determine the electrical conductivity, thermophysical properties and oxidation behavior of FeCr_1.2Ni_1.5Al MPEAs. The initial eutectic microstructure consisted of a disordered BCC (A2) phases and a ordered BCC (B2) phases. The average grain size was ∼ 225μm. The electrical conductivity of FeCr_1.2Ni_1.5Al MPEAs was 1.62 × 10⁶S∕m. The DSC results showed that the FeCr_1.2Ni_1.5Al MPEAs began to melt at 1348^∘C and the liquidus temperature was 1382^∘C. The thermal conductivity increased with the rising temperature, the phonon as well as the electron contributions were assessed. The coefficients of thermal expansion increased with rising temperature, except a slight decrease at around Curie temperature. The kinetic curves of high temperature oxidation were measured at 800^∘C and 1000^∘C, respectively, and obeyed a typical parabolic form. The microstructure and chemical element distribution in different regions of the oxidized sample were analyzed. The Cr₂O₃, Al₂O₃ and FeCr₂O₄ were the majority oxide phases at oxidation temperature of 800 ∼ 1000^∘C. The presence of Al₂O₃ and Cr₂O₃ have detrimental effects on the oxidation resistance at 800^∘C, the Cr₂O₃ and FeCr₂O₄ play a major role at 1000^∘C. CALPHAD calculations helped to explain the oxidation mechanisms. This study confirms the superior oxidation resistance of FeCr_1.2Ni_1.5Al MPEA and suggested it as a perspective candidate in high temperature applications.