Explore the scholarly record.

Abstract

The mechanism by which Cr content variation regulates the microstructure and wear performance of CoCrFeNiTi-series high-entropy alloys (HEAs), in which Cr serves as a principal matrix element, remains unclear, and the relationship between hard-phase precipitation and wear-mechanism transitions also lacks systematic understanding. To clarify these issues, Co1.5CrxFeNi1.5Ti0.3 (x = 0.5, 1.0, 1.5) HEAs were prepared by mechanical alloying (MA) combined with spark plasma sintering (SPS), and the effects of Cr content on microstructural evolution, mechanical properties and dry sliding wear behavior were systematically investigated. The results show that all three alloys consist of an FCC solid-solution matrix together with BCC, Ni3Ti (η), Ni2Ti (R), and (Fe,Cr) (σ) phases. As the Cr content increases from 0.5 to 1.5, the FCC matrix volume fraction decreases from 92.96% to 88.36%, while the η phase increases from 2.65% to 6.76% and evolves from dispersed particles into a continuous network. Cr preferentially dissolves into the FCC matrix, reducing lattice distortion and raising the chemical activity of Ti in the residual matrix, thereby driving continuous η phase precipitation. The influence of Cr content on yield strength is limited (1160.3 - 1197.8 MPa), whereas the compressive strength and hardness increase more markedly (1540.6 - 1874.2 MPa and 410.5 - 469.2 HV0.5), with the x=1.0 alloy exhibiting the best strength–ductility matching. Wear resistance, however, deteriorates monotonically: the coefficient of friction increases from 0.47–0.50 to 0.60–0.64, and the wear rate increases from 1.31×10-4 to 4.22×10-4 mm3 N-1 m-1, with x=1.5 deteriorating by about 222% relative to x=0.5.