Effect of heat treatment on microstructure and mechanical properties of spark plasma sintered AlCoCrFeNiTi0.5 high entropy alloy

The present work is focused on synthesis and heat treatment on non-equiatomic AlCoCrFeNiTi0.5 high entropy alloy (HEA) with a composite structure reinforced by TiC nanoparticles. The initial alloy was prepared by mechanical alloying (MA) in a planetary ball mill, compacted by spark plasma sintering (SPS) and heat treated at different temperatures. Mechano-chemical reactions during the MA process as well as the microstructure and hardness of the SPS-ed compacts prior to and after the heat treatment were investigated. During MA, Cr-based supersaturated solid solution with the BCC structure was formed. After SPS at 1100 \ub0C, the BCC solid solution decomposed into nano-grained microstructure consisting of FCC and ordered BCC solid solutions, σ phase, and in-situ formed TiC nanoparticles. The high hardness of the alloy (762 HV) was retained after the subsequent heat treatment at 1100 \ub0C (603 HV). It was shown that the fabrication of TiC reinforced nanocomposites from elemental powders without the use of expensive nanograined powders can be achieved