Microstructure, mechanical and tribological properties of thermomechanical processed (CoNiCr0.5)95AlxTiy high-entropy alloys

Abstract

The microstructure, mechanical and tribological properties of thermomechanical processed (CoNiCr0.5)95AlxTiy (x = 1, 3, 4 and y = 4, 2, 1 (at.%)) high-entropy alloys (HEAs) were systematically investigated. The low Al and Ti addition is designed to inhibit the formation of precipitation, which is aimed to reach solution strengthening, so as to realize its engineering processing better. The results show that the HEAs mainly contain face-centered cubic (FCC) structure without precipitation. As the Ti/Al ratio increases from 1/4 to 4/1, the average geometrically necessary dislocations (GNDs) density of the HEAs increases from 1.04 × 1014 m−2 to 1.11 × 1014 m−2, and the average Schmid factor decreases from 0.442 to 0.288. Moreover, the ductility, strength, and microhardness of the HEAs change from 13.87%, 910.31 MPa, and 306.12 HV to 10.62%, 1221.09 MPa, and 382.97 HV, respectively. The sliding wear mechanism of HEAs against SiC is mainly composed of abrasive wear and adhesive wear. The increment of Ti/Al ratio improves the tribology performance of HEAs, e.g. the wear rate decreases from 3.95 × 106 mm3/(N·m) to 2.58 × 106 mm3/(N·m) with the increased Ti/Al ratio at a normal load of 7 N.