Tuning composition and microstructure by doping Ti and C for enhancing mechanical property and wear resistance of Al0.2Co1.5CrFeNi1.5Ti0.5 high entropy alloy matrix composites

Spark plasma sintering was used to prepare in-situ synthesized TiC reinforced Al0.2Co1.5CrFeNi1.5Ti0.5 high entropy alloy matrix composites with adding Ti and C elements by the molar ratio of 1:1. Face-centered cubic (FCC) solid solution and in-situ synthesized TiC were the main components of the composite. The content of nanocrystals which induced by grain boundary pinning effect of TiC increased with increasing of Ti and C content. The micro Vickers hardness increased from 410 HV0.3 to 850 HV0.3 and the yield strength increased from 1080 MPa to 2164 MPa when the C content increase to the molar ratio of 2.0. Interstitial solution strengthening, dispersion strengthening, grain-boundary strengthening and fine grain strengthening were the main strengthening mechanisms for the in-situ TiC enhanced Al0.2Co1.5CrFeNi1.5Ti0.5 high entropy alloy matrix composites. The wear resistance of Al0.2Co1.5CrFeNi1.5Ti2.5C2.0 composite was about 40 times higher than that of Al0.2Ca1.5CrFeNi1.5Ti0.5 high entropy alloy. The reinforcing effect of TiC and the protective effect of TiO2 oxide glaze layer which formed by the in-situ tribo-chemical reaction during the friction process were the main reasons for the improvement of wear resistance. (C) 2020 Elsevier B.V. All rights reserved.