Study On Microstructure And Properties Of CoCrFeNi High Entropy Alloy Films Prepared By Magnetron Sputtering

CoCrFeNi,(CoCrFeNi)N_x and CoCrFeNiSi_x films were prepared by direct-current magnetron sputtering.X-ray diffractometer(XRD),scanning electron microscopy(SEM)and atomic force microscopy(AFM)were used to analyze the microstructures of the films.The hardness,resistivity and magnetic properties of the films were tested.The effects of preparation process on the structures and morphologies of the films were investigated.The interaction between composition,structure and properties of these films were proposed.The effects of sputtering power and substrate bias on the structure and properties of the films were investigated.The results show that the CoCrFeNi film is amorphous under lower power,the resistivity is 335???cm,and the saturation magnetization is 361.93 emu/cm~3.At higher power,the films transform to a single face-centered cubic(FCC)structure;The films exhibit<111>preferred orientation with substrate bias.The hardness of the film is as high as11.6 GPa,which was prepared at sputtering power of 80 W and substrate bias of-200 V.(CoCrFeNi)N_x films were prepared at argon plus nitrogen atmosphere by sputtering.The effects of nitrogen flow ratio and substrate bias on the films were proposed.The results show that the(CoCrFeNi)N_x films consist of single face-centered cubic structure with<200>preferred orientation.The nitrogen atom leads a strong solid solution strengthening,which improves the hardness.The grain sizes were decreased and the structures were densified by substrate bias.The hardness could be further enhanced as high as 17.4 GPa under the conditions of R_N=30%and substrate bias of-200 V.Based on the CoCrFeNi films,CoCrFeNiSi_x films were deposited by direct-current magnetron sputtering.At lower Si content(Si 30?),the films exhibit single face-centered cubic structure,while the films with higher Si content(Si 60?~120?)transform to amorphous structure.The substrate bias obviously affects the structure of the films.By high bias,the film exhibits a dual phase structure(face-centered cubic plus body-centered cubic).The hardness is as high as 17.8 GPa under the conditions of Si 90?,80 W and-50 V.CoCrFeNiSi_x films could exhibit paramagnetic properties,the highest resistivity is 6454???cm.