Heat treatment and processing route consequences on the microstructure and hardness behavior of tungsten-containing high-entropy alloys

Abstract

In this work, the effect of metallurgical changes due to heat treatment on the properties of high entropy alloys has been explored. Moreover, the effect of annealing temperature and time on the final microstructure has to be investigated thoroughly. Thus, AlCrFeMnNiWx (X = 0, 0.05, 0.1, 0.5 mol) HEAs have been examined at 800 °C, 1000 °C, and 1200 °C to understand the effect of heat treatment. The HEAs were prepared by vacuum arc melting (VAC) and powder metallurgy route. After that, X-ray diffraction and scanning electron microscopy were utilized to comprehend the microstructure transformation. Furthermore, The HEAs' mechanical characteristics and microstructural evolution were studied after annealing at various temperatures.Interestingly, a dramatic change has been observed in the microstructure in the case of arc melted HEAs. The columnar and equiaxed dendrite was observed after solidification dissolved entirely after the heat treatment at 1200 °C and left dendritic behavior. However, HEA with maximum tungsten content formed some lamellar structure additionally. On the other hand, SPSed HEAs have shown significant phase coarsening and appeared with augmented grain size. In contrast, the evidence of the temperature range of existing of the sigma phase has been verified. Furthermore, energy dispersive spectroscopy has also been employed to confirm the chemical composition and distribution of phases present in the HEAs and presented schematically. Eventually, the composition-microstructure- properties correlation has been established mean by CALPHAD results and comparing the predicted and existing phases for further understanding of phase formation.