Mechanical properties and wear behaviors of FeCoNiCrMnTix high-entropy alloys manufactured by vacuum arc melting

FeCoNiCrMnTix (x = 0, 2, 4, 6 wt%) high-entropy alloys (HEAs) were prepared using vacuum arc melting. The microstructure, mechanical and wear properties of the HEAs were investigated using XRD, OM, SEM, Vickers hardness, tensile tests and friction tests. The crystal structure of the FeCoNiCrMnTix HEAs consists of FCC and BCC, and the precipitation of the strengthening phase Ni3Ti inhibits the FCC to promote the formation of BCC. The dendrites (DR) of the FCC phase enriched with Fe, Co, and Cr. Ni, Mn, and Ti aggregated between the inter-dendrites (IR) of BCC phase. The addition of Ti to FeCoNiCrMn HEA decreased the grain size. FeCoNiCrMnTi6 reaches a maximum microhardness of approximately 293 HV higher than the equiatomic FeCoNiCrMn HEA (∼151 HV). The significant increase in hardness and wear resistance is attributed to solid solution strengthening, grain refinement, and precipitation hardening. With increasing Ti content, the yield strength of FeCoNiCrMnTix HEAs increased from 296 to 601 MPa and the average coefficient of friction (COF) gradually decreased. Tensile fracture is characterized by ductile and brittle fracture. The generated oxide layer protects the alloy matrix during friction, and the wear mechanism gradually transforms from adhesive wear to abrasive wear.