High entropy alloys (HEAs) are multicomponent alloys having constituent elements in equiatomic or near-equiatomic ratios. HEAs with FCC structure have been explored for high temperature applications, for which creep behavior and in turn the diffusion kinetics of these alloys must be understood. In the present work, diffusion kinetics in CoCrFeNi and CoCrFeMnNi is investigated. Radioactive isotopes of Co, Cr, Fe, Mn and Ni are used to determine the tracer diffusion coefficients of all constituents in these HEAs. Applying a quasi-binary approach, the interdiffusion coefficients in CoCrFeMnNi are measured, too, to compare diffusion behaviors in presence of purely entropic and chemical driving forces.
The alloys are prepared by arc melting the constituent elements in equiatomic proportion, followed by homogenization at 1200°C for 50 h. X-ray diffraction and Electron Back-Scatter Diffraction (EBSD) study of these alloys reveal a single phase FCC structure, uniform composition, and grain size in excess of 250 microns.