Delineating Oxidation Aspects of an Additively Manufactured Nanoprecipitation-Strengthened Al_0.2Co_1.5CrFeNi_1.5Ti_0.3...

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_0.2Co_1.5CrFeNi_1.5Ti_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_0.2Co_1.5CrFeNi_1.5Ti_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.