Thermal Stability of Medium- and High-Entropy Alloys of 3d-Transition Metals

A family of high-entropy alloys (HEA) composed of 3d-transitional metals is attracting great interest due to the mechanical, magnetic, and electrical properties that are valuable in the development of advanced structural and functional materials. In this work, we studied X-CoCrFeNi HEAs, where X = Al, Ti, or Cu, produced by mechanical alloying by means of high-energy ball milling. Powder mixture composed of elemental metal powders transforms in a homogeneous alloy (super-saturated solid solution) due to the intense diffusion which takes place during friction and shear deformation of the metal particles during the mechanical alloying. The thermal stability of the HEA phases was experimentally studied in the range 873-1273 K using high-temperature X-ray diffraction and compared with the results of thermodynamic calculations (Calphad).