Influence of Lamella Structure on Mechanical Properties and Corrosion Resistance of AlCoCrFeNi2.1 Eutectic High-Entropy Alloy Fabricated by Laser-Based Directed Energy Deposition

Laser-based directed energy deposition (DED-LB) was employed to fabricate AlCoCrFeNi2.1 eutectic high-entropy alloy at laser powers of 1400 W, 1600 W, and 1800 W. All fabricated specimens exhibited a homogeneous alternating FCC and BCC dual-phase microstructure. The FCC lamellae thickness increased from 240.6 to 566.4 nm with increasing laser power from 1400 W to 1800 W, while the BCC increased from 158.6 to 285.0 nm. The hardness, strength, and ductility decreased with increasing laser power. The 1400 W specimen exhibited the optimal combination of mechanical properties, with a hardness of 337 HV, a yield strength of 737 MPa, an ultimate tensile strength of 1185 MPa, and an elongation of 15.0%. Electrochemical measurements in 3.5 wt.% NaCl solution further demonstrated that the 1400 W specimen possessed the best corrosion resistance, exhibiting the lowest corrosion current density of 3.60 × 10−8 A cm−2 and the most positive corrosion potential of −244.51 mV. Indeed, the strength mechanisms and corrosion resistance are extensively discussed in terms of the lamellar structure during the deposition processes.