Macrostructure, Microstructure, and Mechanical Properties of Al_0.2CoCrFeNi High-Entropy Alloy Produced by Vacuum Induction Melting

Understanding the as-cast structure acts as a precursor, providing insights for alloy processing into a candidate structural material. The recent developments in high-entropy alloys (HEAs) draw attention to explore such domains for their suitability for commercial structural applications. The present work investigates the correlation between the macro-, microstructure, and mechanical properties of a cast single-phase Al_0.2CoCrFeNi HEA. The alloy was produced using a vacuum induction melting route and subsequently characterized using X-ray diffraction (XRD), optical microscopy, and field-emission scanning electron microscopy (FESEM). Mechanical properties were evaluated through uniaxial tensile tests and nanoindentation. The macrostructure of the ingot displayed classical solidification features in both the top and bottom portions. Notably, no macrosegregation was observed in the ingot. However, microsegregation of Al and Ni was detected between the dendritic and interdendritic regions in the top part. Despite the absence of significant variation in macrohardness, the tensile tests revealed noteworthy differences in tensile strength between the top center (330 MPa) and bottom center (464 MPa) of the ingot. This variation in strength was attributed to differences in dendrite arm spacing. Further nanoindentation studies supported the observed tensile behavior, with the top center showing relatively high hardness. This high hardness was found to be correlated with the composition of the dendritic and interdendritic regions.