In this study, nanostructured CoCrFeMoTi high-entropy alloy was synthesized using mechanical alloying . The microstructural features and mechanical properties of this alloy were compared with those of CoCrFeNi high-entropy alloy in order to investigate the influence of the substitution of Ni with Mo and Ti. Internal structure and powder particles morphology changes were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy resolution X-ray analysis (EDS) and transmission electron microscopy (TEM). After 40h of ball milling, two supersaturated BCC solid solution phases were obtained. For the selected alloy system, some physical properties and thermodynamic variables were calculated, including melting point, dissolution enthalpy changes, dissolution entropy changes, atomic size difference, electronegativity difference and valence electron concentration. The calculation results were in full agreement with the criteria for high entropy alloy formation, predicting the formation of high entropy alloy with a BCC solid solution structure. Thermal analysis was carried out with differential scanning calorimeter (DSC) and thermal gravimeter analysis (TGA) at heating rate of 5 for alloyed powders. Results showed that the high-entropy alloys have good thermal stability up to 670 . Consolidation of the alloyed powder was performed by spark plasma sintering under different conditions (temperature, pressure and electrical pulses) and optimized sample selected. Mechanical properties of bulk samples were studied by micro and macro hardness and shear punch tests. Hardness values obtained from macro and micro hardness were 778 and 1031HV, respectively. The values of the ultimate shear stress and yield shear stress were 106 and 81MPa, respectively. Finally, tribological behavior experiment of the optimized sample were carried out by ball on disk for 1000m distances. Results show that the dominant wear mechanisms of CoCrFeMoTi alloy were adhesive and delamination wear at ambient temperature and adhesive wear at elavated temperature. The higher wear resistance of the alloy at higher temperature than the ambient temperature was concluded.
