Effects of Annealing Temperature on the Microstructure and Mechanical Properties of the As-Cast Dual-Phased CoCuFeMnNi High Entropy Alloys Fabricated by Vacuum Induction Melting Method

This research aims to investigate the impact of heat treatment temperatures on the microstructure, hardness, and tensile properties of a CoCuFeMnNi double-phase high entropy alloy (HEA) produced using the vacuum induction melting (VIM) method. The heat treatment temperatures selected (566, 891, and 1064 degrees C) were determined through differential scanning calorimetry (DSC) analysis. The microstructure, structural, and mechanical properties of the heat-treated samples were analyzed using in situ x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), hardness, microhardness, and tensile tests. Evaluation of the microstructure revealed the presence of a-Cu-rich and Cu-lean phases in the as-cast sample. Heat treatment resulted in a change in phase content, with the Cu-rich content decreasing with increasing heat treatment temperature. DSC and in situ XRD analyses confirmed recovery and recrystallization phenomena occurring at temperatures exceeding 891 degrees C. Mechanical tests showed that higher heat treatment temperatures led to a slight decrease in tensile strength but significantly improved failure strain in the as-cast HEA. For instance, the failure strain of as-cast samples after heat treatment at 891 degrees C showed an 84.2% improvement, while the tensile strength only decreased by approximately 5.28%. Additionally, an increase in heat treatment temperature changed the fracture behavior of the as-cast HEA from brittle to ductile.