High entropy alloys (HEAs), along with Multi-principal element alloys (MPEs) and Complexly concentrated alloys (CCAs), offer an exciting, emerging branch of materials research. Unlike conventional alloys, which are usually based on one principal element that, to a large extent, determines the properties of the alloy, these types of alloys consider a wide variety of elements, opening a new field for vast compositions and microstructures, making research into HEAs, MPEs and CCAs tremendously compelling.
About High Entropy Alloys
Considered to be only 12 years old, these complex alloys were introduced in 2004 in two papers that were published a mere two months apart. The definition of HEAs, MPEs and CCAs varies, but in the broadest sense, HEAs are considered to be alloys consisting of five or more principal elements with 5 to 35 atomic percentage for each and based on a simple solid solution, while MPEs and CCAs are considered to be alloys with two or more principle elements.
About the Presentation
In late 2015, Thermo-Calc Software released our first database designed specifically for these complex alloys, the TCHEA database. Dr. Hai-Lin Chen of Thermo-Calc Software recently gave a presentation on its development and its place in this emerging field. The presentation, Calphad Database development for HEMs: Challenges, progresses and prospects, was presented at the International Conference on High-Entropy Materials this November in Hsinchu, Taiwan.
In the presentation, Dr. Chen discussed the challenges faced by developers of HEAs databases, the TCHEA database in particular, and how to tackle those challenges. He then demonstrated that CALPHAD calculations can help to predict/interpret the phase formation and microstructure formation in MPEs by offering several examples and discussing how to properly perform the calculations and interpret the results. The presentation is helpful to understand where we are with HEA database development and where this exciting field is heading.