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.
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. Continue reading