Metal alloys are being designed to resist extreme environments such as high temperatures for applications in nuclear fusion reactors, hypersonic flights, and jet engines. These alloys, known as multi-principal element or medium- to high-entropy alloys, aim to achieve properties like strength, toughness, and corrosion resistance. One challenge faced by researchers is predicting how these alloys will behave under high-temperature oxidative environments. A multidisciplinary research team from the Pacific Northwest National Laboratory and North Carolina State University has combined atomic-scale experiments with theory to create a tool for predicting the behavior of these high-entropy alloys under extreme conditions, allowing for the rapid design and testing of oxidation-resistant metal alloys in industries such as aerospace and nuclear power.
In a recent study, the research team focused on the degradation of a high-entropy alloy known as the Cantor alloy, which consists of equal amounts of cobalt, chromium, iron, nickel, and manganese. By studying the oxide formation on the Cantor alloy, the researchers discovered that chromium and manganese quickly migrate towards the surface to form stable oxides, while iron and cobalt diffuse through these oxides to create additional layers. Adding a small amount of aluminum to the alloy led to the formation of aluminum oxide, which acted as a barrier for other elements migrating to form the oxide, thereby increasing the alloy’s resistance to degradation at high temperatures.
The research sheds light on the mechanisms of oxidation in complex alloys at the atomic scale, providing a deeper understanding of oxidation behavior across all complex alloys. By understanding the fundamental mechanisms involved, the research team has identified universal rules that can predict the oxidation process in complex alloys. Computational models developed by the team allow for the early prediction of oxidation behavior in these alloys, paving the way for the development of complex alloys with exceptional high-temperature properties.
The ultimate goal of the research is to rapidly develop complex alloys with superior high-temperature properties by choosing elements that favor the formation of a protective, stable oxide. The research team plans to introduce automated experimentation and integrate additive manufacturing methods and advanced artificial intelligence to evaluate promising new alloys. This research is part of the Adaptive Tunability for Synthesis and Control via the Autonomous Learning on Edge (AT SCALE) Initiative at the Pacific Northwest National Laboratory, with the goal of expanding knowledge of innovative alloys for various applications.
The research team includes scientists from multiple institutions who used advanced techniques such as in situ atom probe tomography, electron microscopy, synchrotron-based X-ray scattering, and X-ray absorption methods to investigate the atomic structure of the alloys. Results were correlated to understand how elements arrange themselves in the alloy and oxide, contributing to a better understanding of oxidation mechanisms at the atomic level. The study was supported in part by the DOE Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division through the Early Career Research Program, highlighting the importance of this research in advancing materials science and engineering for high-temperature applications.