AlCoCuFeNi high-entropy alloy with tailored microstructure and outstanding compressive properties fabricated via selective laser melting with heat treatment

The present study focused on changes in the microstructures and mechanical properties of AlCoCuFeNi high-entropy alloy (HEA) fabricated via selective laser melting (SLM) and subsequent heat treatment at temperatures of 900 °C and 1000 °C. The as-fabricated sample exhibits a single ordered body-centred-cubic (BCC)(B2) solid solution phase and fine columnar substructure with a strong texture along the layer build-up direction. The heat treatment caused precipitation of the Cu-rich face-centred cubic (FCC) phase from the metastable BCC(B2) matrix, thus forming a dual phase structure in the heat-treated alloys. Heat treatment decreased the microhardness and compressive yield strength, but increased the ductility significantly as compared to the as-fabricated sample. This strength-ductility trade-off is related to the precipitation of the FCC phase, which can toughen the brittle HEA and result in apparent strain hardening. In particular, the sample heat-treated at 1000 °C exhibited a better compressive fracture strength of 1600 MPa, a yield strength of 744 MPa, and a strain of 13.1%. The improvement in mechanical properties is mainly attributed to the effective combination of the BCC(B2) and FCC phases. This study provides novel insights into the fabrication of AlCoCuFeNi HEAs with tailorable microstructures and superior mechanical performance via a combined process of SLM and subsequent heat treatment.