Optimizing Mechanical Properties of AlCoCrFeNiTix High-Entropy Alloys by Tailoring Microstructures

The effects of Ti addtions and the heat treatment on the mechanical properties of AlCoCrFeNiTix (x = 0, 0.2, 0.3, 0.4 and 0.5) high-entropy alloys (HEAs) were studied. The results show that the dendrite phase with a body-centered-cubic (bcc) structure transforms into the interdendrite phase with a new bcc structure. With the increase of the Ti contents and heat-treatment temperature, the average hardness and yield strengths are greatly improved, and the highest hardness and yielding strength are 583 HV and 2.07 GPa, respectively in the investigated HEA system. The as-cast and annealed HEAs exhibit excellent mechanical properties, combining with high yielding strength and plasticity. The solid solution strengthening mechanism of Ti additions is responsible for the strengthening effect of AlCoCrFeNiTix HEAs.