Nanoindentation mechanical properties of CoCrFeNi high entropy alloy films

CoCrFeNi high-entropy alloy films were deposited under different substrate bias by magnetron sputtering using a simple splicing target. The hardness, elastic modulus and creep properties of the films were measured by nanoindentation. The results showed that with the increase in substrate bias, CoCrFeNi films were always mainly composed of FCC phase and demonstrated smooth and dense surface with uniform distribution of elements, but the preferred orientation of the films changed from FCC (200) to no preferred and then to FCC (111). The hardness and elastic modulus of CoCrFeNi films were not sensitive to the strain rate of nanoindentation (0.05-0.15 s(-1)). The maximum hardness of the film was about 10.4 GPa under the substrate bias of -50 V, while the maximum elastic modulus of 249.8 GPa appeared under the substrate bias of -200 V. The applied negative substrate bias (-50 V similar to -200 V) could improve the elastic modulus and creep properties of the films.