Tribological and mechanical properties of surface nanocomposite AlCoCrFeNi2.1 high-entropy alloy produced by FSP

Abstract

In the present work, the nanocomposite AlCoCrFeNi2.1 high-entropy alloy was produced using friction stir processing (FSP) with the addition of TiO2 nanoparticles. The size and weight percent of added nanoparticles were 30 ± 5 nm and 3 wt%, respectively. The applied rotating and transvers speeds were 800 rpm and 50 mm/min, respectively. The microstructural evolutions, the hardness changes, the shear properties and the tribological behavior were evaluated after applying FSP. These studies were carried out using X-ray fluorescence (XRF), optical microscopy, scanning electron microscopy (SEM), energy dispersive X-Ray analysis (EDX), X-Ray diffraction (XRD), Rockwell C and Vickers hardness testing, shear punch testing (SPT) and pin-on-disk wear test. After the FSP, the hard B2 phases, which were formed during casting, were broken and along with the TiO2 nanoparticles distributed uniformly in the matrix. These changes resulted in increase in hardness and shear strength from 301 HV to 485 HV and 332–411 MPa amounts, respectively for initial and FSPed cases; however, the wear resistance of the FSPed specimen decreased by approximately 60% compared to the initial condition.