Weak enthalpy-interaction-element-modulated NbMoTaW high-entropy alloy thin films

Highlights: • The thermal stability of (NbMoTaW)_100-xV_x films are evaluated. • Surface current distribution are performed to character the compositional status. • Relationship between local structure and the properties of the films was studied. • The local structure is interpreted according to the cluster plus glue atom model. • The effect of V on the microstructure and properties of the films are discussed. A local structure determines the properties in disordered solid solutions with simple crystal structure. Introducing a weak enthalpy-interaction-element will change the local structure evolution of refractory high-entropy alloy films, thereby bringing effects for the properties. Herein series of (NbMoTaW)_100-xV_x (x = 0 ~ 30.5, at%) thin films were prepared by radio frequency magnetron sputtering, and systematic investigations of the films are carried out through combining the underlying microstructure, mechanical properties, and resistivity-temperature behavior. Furtherly, in accordance with the cluster-plus-glue-atom model, the present paper interpreted the local structure evolution with the film components changing. The results reveal that the excellent thermal stability of the films is originate from the enthalpy interaction, and the high stability of the refractory element itself. The V addition is free of crystal structure variation in the films, but bringing two-fold effects. The main one is the enhancement of the microstructural homogeneity by increasing the disorder degree. The other is weakening interatomic interactions as well as enabling the films more unstable due to the increasing system energy. The refractory high-entropy films can be promising candidates for high temperature, high hardness, and wear-resistance applications, e.g., high-temperature-bearing structures, heat-protection systems, diffusion barriers, and film resistors.