Synergistic enhancement of high-temperature oxidation resistance in lightweight AlFeCrMnTi high-entropy alloy via BCC phase and L21 nano-coherent precipitates

Abstract

This study investigates the high-temperature oxidation behavior of a lightweight, non-equiatomic AlFeCrMnTi high-entropy alloy (LWHEA) with a density of 6.29 g/cm 3 . The alloy exhibits a dual-phase microstructure consisting of a Cr- and Mn-rich BCC matrix and L2₁(Fe 2 AlTi) nano-precipitates. High-temperature cyclic oxidation tests at 700 °C, 800 °C, and 900 °C reveal superior oxidation resistance , with parabolic rate constants of 2.10 × 10 −8 mg 2 ·cm −4 ·s −1 and 1.02 × 10 −7 cm −4 ·cm cm −4 ·s −1 at 700 °C and 800 °C, respectively. At 900 °C, the oxidation rate increases due to the formation of MnO 2 impurities, which compromise the protective Al 2 O 3 oxide layer. The exceptional oxidation resistance at lower temperatures is attributed to the synergistic interaction between the BCC phase and L2₁ precipitates, which promote the formation of a dense and continuous Al 2 O 3 film. This work provides a comprehensive model for enhancing oxidation resistance in lightweight high-entropy alloys through microstructure optimization, offering significant economic and performance benefits for high-temperature applications.