High-temperature oxidation behaviors of Co-free Cr30Fe30Ni30Al5Ti5 dual-phase multi-component alloys with multi-scale nanoprecipitates

In the context of the growing research interest in multi-component alloys (MAs) and their exceptional performance under extreme environments, the high-temperature oxidation resistance and applications of MAs have attracted significant attention in the field of metallic materials. While the cost-effective and mechanical properties of Co-free MAs are of great importance, their oxidation resistance remains insufficiently understood. In this work, we designed multiple heterogeneous structures within a cast dual-phase CrFeNiAlTi MA by tailoring the Al and Ti ratio, which consists of body-centered-cubic (BCC) grains reinforced by multi-scale nanoprecipitates (i.e., L2, B2, and phase) and an L1-strengthened face-centered cubic (FCC) skeleton. Isothermal oxidation experiments at 800 °C, 1000 °C, and 1200 °C with varying exposure durations were conducted. The oxidation kinetics at 800 °C and 1000 °C followed a parabolic law, while both low weight increment and oxidation rate confirm remarkable oxidation resistance. At 800 °C, the oxides mainly consist of CrO and AlO, while are dominated by (TiO + CrO) and the mixed oxides of AlO, TiO and TiO above 1000 °C. Importantly, the inability to form a continuous AlO oxide scale at higher temperatures led to a deterioration in oxidation resistance. These findings offer valuable insights into underlying mechanisms contributing to oxidation resistance for Co-free MAs.