Thermal stability and high-temperature oxidation behavior of coherent precipitation-strengthened Cu-based multi-component alloys

Abstract

To address the current gap in systematic understanding of microstructural stability and high-temperature oxidation resistance in the novel L1₂ phase precipitation-strengthened Cu-based multi-principal-element alloy, in this study, the evolution of precipitated phases, coarsening kinetics during long-term thermal exposure, and high-temperature oxidation mechanisms were investigated by using multi-scale characterization techniques in combination with first-principles calculations and thermodynamic calculations. The results demonstrate that the multi-component L1₂ phase in the alloy exhibits excellent thermal stability between 650 °C and 750 °C, with a slow coarsening process. In contrast, grain boundary precipitates still experience discontinuous coarsening during prolonged thermal exposure, which may have an adverse effect on the stability of microstructure and properties. Thus, further optimization and precise regulation of the alloy system remain imperative for future research. During oxidation at 850 ~ 990 °C, the oxidation kinetics of the alloy generally conform to a parabolic law, indicating robust and sustained oxidation resistance. A multi-layered oxide film structure forms on the alloy surface, consisting of Al₂O₃, a spinel phase, and outer complex oxides. Notably, the continuous Al-rich oxide layer and multi-component spinel layer synergistically inhibit the diffusion of oxygen and metal ions, thereby significantly enhancing oxidation resistance. Thus, the improved high-temperature performance results from precipitation of stable multi-component L1₂ phase and protective multi-component oxide formation through selective oxidation of Al and Cr.