EFFECT OF CRYOTREATMENT ON THE MICROSTRUCTURAL EVOLUTION OF Ti-Al-Ni-Cr-Co-Fe BASED HIGH ENTROPY ALLOY

Abstract

High Entropy Alloys (HEAs) are new class of materials. Recent Studies on HEAs have attracted much attention in the field of scientific research and industry. There has been a lot of interest in HEA compositions having a BCC structure. However, analysis of deep cryotreated Ti-Al-Ni-Cr-Co-Fe-based alloys on the structure and mechanical behavior of these BCC HEAs has not been performed so far. This project aims to determine the impact of deep cryogenic treatment on those factors by investigating the phase composition, microstructure, and characteristics of the TiAlNiCrFe and TiAlNiCrCo high-entropy alloys. Through the ball milling of elemental powders and Spark Plasma Sintering, multicomponent alloys of TiAlNiCrFe and TiAlNiCrCo were effectively created. XRD patterns showed that both materials had substantial two-BCC phases after Spark plasma sintering. In the TiAlNiCrFe and TiAlNiCrCo samples, SEM BSE images of the microstructure samples showed a fine dispersion of the two BCC phases coupled with a fine dispersion of TiC nanoparticles. The impact of deep cryogenic treatment on the phase composition, crystallite sizes, microstructure, and mechanical characteristics of TiAlNiCrFe and TiAlNiCrCo high-entropy alloys were successfully investigated. The XRD patterns say that the 4 and 8-hour treated TiAlNiCrFe and TiAlNiCrCo samples show major BCC peaks similar to as-sintered alloys, and small TiNI3 peaks are also present in both 4,8-hour treated alloys. Hardness seemed to rise initially before decreasing as the duration of the cryogenic treatment increased. At 4-hourly treated samples have finer crystallite sizes and maximum hardness was attained. The hardness value of TiAlNiCrFe alloy after 4-hour treatment rises from 755 HV to 840 HV by 11.25%.