Effect of Ti as co-sputtering target on microstructure and mechanical properties of FeCoNi(CuAl)0.2 high-entropy alloy thin films

Three different FeCoNi(CuAl)0.2 alloy films sputtered with Ti were prepared using magnetron sputtering: single sputtering films of FeCoNi(CuAl)0.2 target, co-sputtering films of FeCoNi(CuAl)0.2/Ti targets, and alternating sputtering composite films of FeCoNi(CuAl)0.2/Ti targets. SEM, XRD, AFM and nano indentation analysis showed that with the increase in Ti content and change in sputtering mode, the main phase structure of the film changed from FCC to BCC. The hardness and elastic modulus of FeCoNi(CuAl)0.2/Ti target co-sputtered films reached 7.33 GPa and 145 GPa, respectively. This can be attributed to the large atomic radius of Ti dissolved in the FeCoNi(CuAl)0.2 system that caused phase transformation and significant lattice distortion.