Silicon-content-dependent microstructures and mechanical behavior of (AlCrTiZrMo)-Six-N high-entropy alloy nitride films

The multi-component (AlCrTiZrMo)-Six-N high-entropy films with different silicon contents were deposited on the silicon substrate by magnetron sputtering. The influence of silicon contents on the structures and properties of the films was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), electron probe microanalyzer (EPMA) and nanoindentation. The results show that the (AlCrTiZrMo)N film without silicon has columnar crystals and the (200)-preferred direction. With the increase of the silicon content, the films gradually change from columnar grains with a (200) preferential orientation to structures with amorphous phases (amorphous phases are the state of near order and long disorder in the arrangement of atoms in a solid state) containing nanocrystals (nanocrystallites are single-phase (AlCrTiZrMo)N of grains with a size of 5–10 nm) with finer grains. As the silicon content increases, the mechanical properties of the films first increase then decrease. Thus, when the silicon content is 4.5 atomic percent (at.%), the film obtained possessed comprehensive mechanical properties with the maximum hardness and modulus values of 28.5 GPa and 325.4 GPa, respectively. The results show that the improvement of hardness and modulus is mainly attributed to the microstructures of the films.