Delineating Oxidation Aspects of an Additively Manufactured Nanoprecipitation-Strengthened Al _0.2 Co _1.5 CrFeNi _1.5 Ti _0.3 High-Entropy Alloy

The recent perspective of multiprincipal element alloys (MPEAs), also known as high-entropy alloys (HEAs), has emerged as a very promising area for material design. Additive manufacturing (AM) strategies have also been noted to provide additional strength to HEA systems. In the selected dual-nanoprecipitation Al 0.2 Co 1.5 CrFeNi 1.5 Ti 0.3 HEA system, an additional strength of approximately 300–400 MPa was achieved by adopting an additive manufacturing route as compared to its cast and wrought counterparts. However, the challenge of oxidation degradation always imposes a severe limitation for high-temperature applications in gas turbines, power plants, and aerospace components. Hence, ensuring material sustainability, longevity, and integrity for high-temperature applications inevitably requires the exploration of the oxidation behavior of alloys. In the current study, the oxidation performance of Al 0.2 Co 1.5 CrFeNi 1.5 Ti 0.3 HEA, in as-printed as well as nanoprecipitation-strengthened aged states, was evaluated from 600°C to 1200°C. A comparative framework elucidating the mechanistic aspects and elemental redistribution of nanoprecipitates on oxidation behavior has been highlighted. In both the as-printed and aged states, the alloys followed subparabolic oxidation weight gain kinetics below 900°C. However, the thickness growth kinetics exhibited parabolic behavior above 900°C. The oxide layer exploration manifested the formation of a homogeneous Cr-oxide layer, which acts as a protective barrier against oxidation activity. The impact of atomic size on mobility also played a significant role in suppressing the formation of outer Al and Ti oxide layers, instead of having a lower reduction potential compared to Cr.