Insight into the oxidation behavior and excellent internal oxidation and nitridation resistance of Fe_71.5-x(Ni, Cr, Ti)_28.5Al_x complex concentrated alloys by advanced characterization

For precipitate-strengthened alloys, the decomposition of the precipitates at the subsurface during high-temperature oxidation is detrimental to mechanical properties. In this study, we adjusted Al concentrations in Fe_71.5-x(Ni, Cr, Ti)_28.5Al_x (x = 8, 12, and 16 at%) complex concentrated alloys (CCAs) to precipitate elongated cuboidal L2₁ with higher density and Al concentration, as well as reduced inter-precipitate spacing. This is more conducive to the rapid diffusion of Al to the matrix and grain boundaries, promoting the formation of a continuous and compact Al₂O₃ layer with random crystallographic orientation at 800 °C in air. This not only inhibits the further decomposition of the L2₁ phase but also avoids internal oxidation and nitridation.