Microstructure and Properties of AlCoCrFeNi2.1Nbx High-Entropy Alloys Prepared by Selective Laser Melting

Herein, Nb element is introduced into the AlCoCrFeNi2.1 eutectic high-entropy alloy to create a heterogeneous structure. AlCoCrFeNi2.1Nbx (x = 0, 0.25, 0.5) eutectic high-entropy alloys (HEAs) are fabricated using selective laser melting technology. The forming characteristics, microstructure, and mechanical properties of the AlCoCrFeNi2.1Nbx eutectic HEAs are investigated. The results show that the relative density of the samples increase and then decrease. The optimal process parameters are determined as laser power of 50 W, scanning speed of 400 mm s(-1), scanning spacing of 70 mu m, and layer thickness of 30 mu m. The primary microstructure of AlCoCrFeNi2.1Nbx alloys (x > 0) consists of a hypoeutectic structure comprising body-centered cubic, face-centered cubic, and Fe2Nb-type Laves phases. With the addition of Nb element, the hardness of the high-entropy alloy increases from 600.6 to 774 HV, the yield strength increases from 664.1 to 1091.9 MPa, while the ductility slightly decreases. Furthermore, the strengthening mechanisms of the alloy are attributed to the precipitation strengthening and solid solution strengthening of the Laves phase, as well as the grain refinement effect. The wear resistance of the alloy improves gradually with the increasing Nb content, and AlCoCrFeNi2.1Nb0.5 exhibits the best wear resistance, primarily through adhesive wear.