Laser powder bed fusion of an Al-Cr-Fe-Ni high-entropy alloy produced by blending of prealloyed and elemental powder: Process parameters, microstructures and mechanical properties

Abstract

High-entropy alloys in the Al-(Co)-Cr-Fe-Ni system have been designed along several pathways to obtain tailored microstructures with remarkable mechanical properties, such as high strength and ductility. Additive manufacturing techniques, such as laser powder bed fusion, have been utilized and aim towards further optimization of their mechanical properties. However, processing challenges exist for these promising alloys, mainly due to their crack susceptibility as recently shown in the Co-free Al-Cr-Fe-Ni alloy. In this study, gas atomized prealloyed powder of a baseline Al-Cr-Fe-Ni high-entropy alloy was mixed with Fe and Ni elemental fine powder particles, to produce a powder blend with a modified composition. It was aimed to improve the alloy processability via designing the solidification path by reducing the Al content. The synthesized novel alloy composition was processed by laser powder bed fusion and crack-free material with a metastable, near single-phase face-centered cubic microstructure was obtained. Process parameters for minimum porosity were identified and net-shape tensile specimens were produced. Heat treatment led to a refined dual-phase microstructure consisting of face-centered cubic and body-centered cubic phases with promising mechanical properties, such as high tensile strength, reasonable elongation and notable strain hardening.