Phase transformation and diffusion in high-temperature oxidation of FeCrNi medium entropy alloy

The oxidation of the FeCrNi medium entropy alloy is investigated from 700 to 1000 degrees C by combining experimental observations with density functional theory (DFT) calculations. The sole oxidation product formed is Cr2O3. At 900 degrees C, the layer exhibits desirable density and continuity, attributed to the rapid diffusion of Cr facilitated by the body-centered cubic phase transformation. There is a significant increase in mass gain rates at 1000 degrees C, accompanied by the formation of a discontinuous Cr2O3 layer and penetration of oxide. These observations emphasize the significant roles of phase structure in promoting the formation of protective oxide scales and influencing oxidation resistance.