Experimental investigation of the local environment and lattice distortion in refractory medium entropy alloys

EXAFS analysis of pure elements, binary and ternary equiatomic refractory alloys within the Nb-Zr-Ti-Hf-Ta system is performed at the Nb and Zr K-edges to analyze the evolution of the chemical local environment and the lattice distortion. A good mixing of the elements is found at the atomic scale and similar distances are obtained between the central atom and its neighbors, except for NbHf and NbTiZr that have a wider distribution of the nearest neighbors' distances, suggesting a distortion of the structure. The Debye-Waller parameters show some correlation with the lattice distortion parameter, and allows to quantify experimentally the static disorder in medium entropy alloys.