Preparation of ultrahigh-strength and ductile nano-lamellar eutectic high-entropy alloy via laser powder bed fusion

Abstract

The AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) has become one of the hottest research topics owing to its comprehensive mechanical properties. In this study, the AlCoCrFeNi2.1 EHEA was fabricated via the laser powder bed fusion (L-PBF) technique, and the grain morphology, eutectic structure, mechanical properties, and deformation mechanism were investigated. The results indicate that the samples have superfine grains and nano-lamellar eutectic structures, attributable to the high cooling rate of the L-PBF process. Furthermore, the phenomenon of solute trapping was observed in the boundary of the FCC and B2 semi-cohesive phase in the nano-lamellar eutectic structure. Based on the special eutectic structure of the AlCoCrFeNi2.1 EHEA prepared using the L-PBF technique, the samples exhibited an exceptional tensile strength of up to 1.6 GPa, accompanied by tensile ductility of over 9.5 %. The improvement of mechanical properties may be attributable to the Hall–Petch strengthening and back stress effect caused by refining the eutectic structure, whereas the growth of the nano-lamellar structure may be closely related to the solute-trapping effect.