High-entropy transition metal nitride thin films alloyed with Al: Microstructure, phase composition and mechanical properties

•(TiHfNbVZr)1-xAlxN and (TiHfNbVZrTa)1-xAlxN high-entropy nitride thin films are synthesised utilizing a hybrid PVD method.•The hexanary and heptanary thin films are based on single-phase fcc-NaCl structured solid solution.•Al concentration in high-entropy nitride thin films determines hardness, yield strength, toughness, and plastisity.•The solid solution is stable up to x~0.51-0.61 and up to x ~0.45-0.64 for the hexanary and heptanary films, respectively.•Mechanical properties are determined by deformation mechanisms arising from the electronic structure and phase composition.