Effect of manufacturing route on microstructure and micromechanical properties of AlCoCrFeNi high entropy alloy

The manufacturing route of a particular metallic alloy profoundly affects its microstructure, as well as mechanical properties. In that respect, the present research investigates the microstructure and microstructuredependent mechanical properties of the AlCoCrFeNi high entropy alloy (HEA), that was manufactured via two different routes: (i) Atmospheric plasma spraying (APS) in the form of coating on a stainless steel subtract and (ii) vacuum arc melting (VAM) in the form of bulk material. AlCoCrFeNi HEA coating microstructure is composed of a solid solution (Ni) as a matrix, which contains different phases, as well as intermetallics and defects, such as splat boundaries. On the contrary, the microstructure of bulk AlCoCrFeNi HEA alloy is free from any secondary phases, and is homogeneous in nature, which consists of only the solid solution of Ni. The experimental results show that the strength of the bulk HEA (963.14 f 28.58 MPa of yield strength and 1005.58 f 22.08 MPa of compressive strength) is better than that of HEA coating (yield strength of 802.33 f 43.76 MPa and compressive strength of 817.73 f 43.84 MPa). The phase, as well as splat boundaries in the microstructure, are the 'weakest link' in the HEA coating, that serves as defect initiation site. As the bulk HEA alloy is free from these 'weakest link', thus, deformation of the material is guided through plastic flow of materials, in the terms of the barrelling effect.