Anisotropy study of the microstructure and properties of AlCoCrFeNi2.1 eutectic high entropy alloy additively manufactured by selective laser melting

Abstract

• The maximum density of SLM-printed AlCoCrFeNi2.1 EHEAS is 99.1%. • Differential texture anisotropy of the specimen perpendicular and parallel to the building direction. • The grain size of the X – Y plane was larger than that of the X – Z plane. • The hardness of the X – Y surface was higher than that of the X – Z surface. • SLM EHEAs have better performance compared with those of traditionally manufactured counterparts. The AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) was prepared by selective laser melting (SLM), focusing on the anisotropy of microstructure and mechanical performance. The AlCoCrFeNi2.1 EHEA printed by SLM has face-centered cubic (FCC) and body-centered cubic (BCC)/B2 phases, and the FCC phase accumulates at the boundary of the molten pool. With the increase in volumetric energy density (VED), the content of the FCC phase parallel to the surface in the direction of the building increases from 30.9% to 41%. The X–Z plane mainly produces columnar crystals along the temperature gradient, while a large number of equiaxed crystals are produced in the X–Y direction. When the volume energy density is 157 kJ/mol (VED 157), the average grain size is 1.33 µm for BCC and 1.14 µm for FCC, which is significantly smaller than other preparation methods. Due to defect distribution and size, the microhardness of the X–Y plane is generally higher than that of the X–Z plane, with maximum hardnesses of 660 HV and 655 HV, respectively, which is much higher than those of traditionally manufactured counterparts. The compression performance of SLM process AlCoCrFeNi2.1 EHEAs shows maximum yield strength of 1567 MPa, and the ultimate compressive strength can reach 3276 MPa.