Laser Beam Welding of CoCuFeMnNi High Entropy Alloy: Processing, Microstructure, and Mechanical Properties

The present work explores the feasibility of joining the CoCuFeMnNi high entropy alloy by laser beam welding. An appropriate feasibility window is identified, and the optimal process parameters (300 W power, scanning speed 20 mm s(-1), spot size 0.45 mm) are related to the properties of the studied material. Cu's tendency to segregate from other alloying elements is found to dominate the microstructural evolution: the welding process induced the formation of Cu-rich second phases within the melted zone (MZ), as interdendritic phase, as well as in the heat-affected zone (HAZ) as grain boundary phase. Mechanical resistance of the welded beads and the HAZs was improved (187 HV on average) over one of the base materials (BMs) (160 HV on average) owing to the formation of Cu-rich phases and solidification stresses. Consequently, tensile strength (576.4 MPa) and elongation to failure (28.3%) are almost the same as in the BM. Indeed, failure during tensile tests always took place outside the welded bead, therefore confirming the extreme soundness of the performed laser beam welding. Such results confirm that laser welding may be safely applied to relatively complex high entropy alloys (HEA), thus easing their practical application.