New Advances in High-Entropy Alloys

In recent years people have tended to adjust the degree of order/disorder to explore new materials. The degree of order/disorder can be measured by entropy and it can be divided into two parts: topological disordering and chemical disordering. The former mainly refers to order in the spatial configuration e.g. amorphous alloys which show short-range ordering but without long-range ordering while the latter mainly refers to the order in the chemical occupancy that is to say the components can replace each other and typical representatives are high-entropy alloy (HEAs). HEAs in sharp contrast to traditional alloys based on one or two principal elements have one striking characteristic: their unusually high entropy of mixing. They have not received much noticed until the review paper entitled Microstructure and Properties of High-Entropy Alloys was published in 2014 in the journal of Progress in Materials Science. Numerous reports have shown they exhibit five recognized performance characteristics namely strength-plasticity trade-off breaking irradiation tolerance corrosion resistance high-impact toughness within a wider temperature range and high thermal stability. So far the development of HEAs has gone through three main stages: 1. Quinary equal-atomic single-phase solid solution alloys; 2. Quaternary or quinary non-equal-atomic multiphase alloys; 3. Medium-entropy alloys high-entropy fibers high-entropy films lightweight HEAs etc. Nowadays more in-depth research on high-entropy alloys is urgently needed.