High-strength AlCoCrFeNi2.1 eutectic high entropy alloy with ultrafine lamella structure via additive manufacturing

Abstract

AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA), with its unique in-situ composite structure, not only overcomes the shortcoming of insufficient strength for face-centered-cubic (FCC) single-phase high entropy alloy (HEA), but also overcomes the shortcoming of insufficient ductility for body-centered-cubic (BCC) single-phase HEA, thus attracting widespread attention from the academic community. In this study, AlCoCrFeNi2.1 EHEA with a fully nano-lamella structure was prepared by selective laser melting (SLM). Furthermore, massive L12 and BCC nano-precipitates were precipitated out from the FCC and B2 phases, respectively. Compared to AlCoCrFeNi2.1 EHEA prepared by traditional methods, the SLM-ed EHEA sample shows excellent strength and ductility synergy, with the yield strength, ultimate tensile strength and uniform elongation determined as 1329 ± 12 MPa, 1621 ± 16 MPa and 11.7 ± 0.5%, respectively. The strengthening contributions to the high yield strength of the sample come from nano-lamella structure, grain boundaries, dislocations and nano-precipitates. In addition, wear behavior at room temperature and elevated temperatures of the SLM-ed EHEA sample have also been studied. The tribological property is substantially enhanced with increasing temperature from room temperature to 700 °C due to the transformation in wear mechanism from adhesive wear to oxidative wear.