Microstructures and properties of AlCoCrFeNi2.5 eutectic high entropy alloy fabricated by selective laser melting

Eutectic high entropy alloy has attracted much attention due to its excellent properties, such as outstanding ductility, strength, and wear resistance. In this study, AlCoCrFeNi2.5 eutectic high entropy alloys with nearly full relative density and no cracks were successfully fabricated by selective laser melting and annealed at 700 °C and 900 °C, respectively, and then the microstructures and properties were studied in detail. The fabricated AlCoCrFeNi2.5 had a high relative density with a maximum of 99.723% when the VED was 107.13 J/mm3. The SLM-as built showed two different morphological characteristics: cellular structure and columnar crystal. And the SLM-HT (700 °C) and SLM-HT (900 °C) showed lamellar structure and irregular dendrite and eutectic structure, respectively. The SLM as-built and SLM-HT specimens both consisted of face-center cubic (FCC) and body-center cubic (BCC) phase. The FCC phase of the SLM-as built and SLM-HT specimens both performed a Cube {100} <001> texture, and with the increase of annealing temperature, the texture density decreased. And the BCC phase of the SLM-HT (700 °C) specimen showed the strongest texture density due to the low annealing temperature and the formation of BCC phases. Compared with SLM as-built, the ultimate tensile strength of SLM-HT (700 °C) had increased from 1088 MPa to 1278 MPa, and the elongation had decreased from 18.3% to 15.6%; the ultimate tensile strength and elongation of SLM-HT (900 °C) were 1228 MPa and 19.5%, respectively. The current results provide a new manufacturing processing and heat treatment way to overcome the trade-off between the strength and ductility of eutectic high entropy alloy.