A novel antioxidant strategy for refractory high-entropy alloys utilizing element diffusion along an ultrafine lamellar microstructure

Abstract

High-temperature oxidation poses a significant challenge in applications such as aviation and turbines. While refractory high-entropy alloys maintain good strength at elevated temperatures, their resistance to high-temperature oxidation remains problematic. To explore an antioxidant strategy for refractory high-entropy alloys, the oxidation behaviour of Ti2ZrNbNi3 with an ultrafine body-centered cubic disordered and ordered solution (BCC + B2) lamellar microstructure was studied at different temperatures. When the oxidation temperature is greater than 800 °C, O atoms diffuse inwards along the boundaries of the ultrafine lamella and combine with Zr and Ti to generate low-valent oxides. With increasing time, high-valent oxides of Zr and Ti are generated, and Ni atoms originally belonging to the B2 phase can diffuse outwards and then form a dense NiO antioxidation layer. As the oxide rate of Ti2ZrNbNi3 is as low as that of pure Ni, the effectiveness of an antioxidation strategy utilizing elemental diffusion along an ultrafine lamellar microstructure has been demonstrated.