This is a scanning electron microscope backscattering image of an alloy comprising molybdenum (Mo), tungsten (W), tantalum (Ta), titanium (Ti) and zirconium (Zr). The brighter contrast shows the (Mo, W, Ta)-based solid solution, while the darker phase is the (Ti, Zr)-rich phase. Image: Ames Laboratory.The US Department of Energy's Ames Laboratory has developed a method of computational analysis that can help predict the composition and properties of as-yet-unmade high-performance alloys. They report this new method in a paper in npj Computational Materials.
Made up of four or more metallic elements, so-called high-entropy alloys are highly sought after for their simple structures, excellent mechanical properties over a wide range of temperatures, and improved oxidation or corrosion resistance. Advances in these materials could lead to enhanced jet engine performance and fuel efficiency, as well as other applications in industries where mechanical parts must operate in harsh environments.
"What's traditionally been done in materials design is tweaking what we know about materials that have already been discovered, and we know that even small changes in the composition of alloys can result in big changes to their properties," said Duane Johnson, Ames Laboratory scientist and computational theorist. "But that means there's a ton of undiscovered territory out there, especially in alloys made of four or more elements."
Given the sheer number of possible ways four or more elements can be combined, it would be difficult for experimentalists to know where to look for the next new high-entropy alloy. What is more, high-entropy alloys are notoriously difficult to make, requiring expensive materials and specialty processing techniques. Even then, attempts in a laboratory don't guarantee that a theoretically possible compound is physically possible, let alone potentially useful.
"A good place to start then," said Johnson, "is being able to tell experimentalists where NOT to look." Using a high-throughput computational approach, the researchers used a unique electronic-structure method to predict properties of any arbitrary high-entropy-alloy composition. This involved simultaneously assessing their ability to form a solid solution in simple structures, their atomic ordering, their chemical stability, and their mechanical properties at changing temperatures.
"Our calculations answer a number of questions, the most important being 'is it even worth looking here?'" said Johnson. "We can narrow down the design space for multi-component systems, and circle the area(s) on which to focus for the most promising materials for investigation or development."
This story is adapted from material from Ames Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.