High-strength AlCoCrFeNi2.1 eutectic high entropy alloy skeleton with hollow brick wall structures by selective laser melting

Abstract

In this work, a hollow brick wall structure was introduced into the preparation of AlCoCrFeNi2.1 EHEA to realize a skeleton structure by taking advantage of the good castability of eutectic high entropy alloys (EHEAs) and high cooling rate of selective laser melting (SLM). The effects of processing parameters on eutectic microstructure and mechanical properties of SLM-ed AlCoCrFeNi2.1 EHEA skeletons were investigated. With increasing volume energy density (VED), the microstructure along the building direction evolved from cellular structure to the coexistence of cellular and lamellar structures. The phases in the SLM-ed AlCoCrFeNi2.1 EHEA skeletons contained BCC/B2 and FCC phases. Under the VED of 137.25 J/mm3, SLM-ed skeletons with hollow brick wall structures had a compressive strength of 241.2 ± 4.2 MPa. The mechanical properties from tensile tests exhibited a yield strength of 1349.4 ± 12.4 MPa and an ultimate tensile strength of 1529.5 ± 12.8 MPa. The superior performance of the selective laser melting method was attributed to fine grain strengthening, dislocations strengthening, and heterogeneous structure of FCC and BCC/B2. This work provides possibilities for microstructure design and performance improvement of EHEAs and expands the avenue for developing advanced high-strength lightweight structural and energy-absorbing alloys.