Balanced mechanical properties of Al0.5CoCrFeNiTi0.1 high entropy alloy under extreme environments from cryogenic temperature to 800 °C

The advancement of modern industry requires the development of high-performance materials capable of operating in extreme environments, such as at cryogenic and high temperatures. Face-centered cubic (FCC) high entropy alloys (HEAs) show remarkable mechanical properties at low temperatures caused by nano-twinning. However, their strength is insufficient at both room and elevated temperatures. To address this issue, we attempted to develop Al 0.5 CoCrFeNiTi 0.1 HEA, which consists of FCC matrix and L2 1 precipitates, with excellent mechanical properties at various temperatures. The evolutions of microstructures and mechanical properties were examined by experimental efforts coupled with theoretical approaches, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), tensile tests at room temperature and theoretical strengthening calculations. Additional tensile tests were conducted at cryogenic (-160 °C) and high temperatures (600–800 °C). The ultimate tensile strength (UTS) at room temperature was measured as 1097.5 MPa, while values at −160, 600, 700 and 800 °C were identified to be 1398.0, 707.2, 548.2 and 332.7 MPa, respectively. These results revealed outstanding mechanical properties compared to other FCC-based alloys. • The addition of Ti in Al 0.5 CoCrFeNi HEA leads to the formation of L2 1 precipitates. • The size and volume fraction of precipitates depends on the aging conditions, causing variation in mechanical properties. • The primary strengthening mechanism is precipitation-hardening via Orowan strengthening. • The Al 0.5 CoCrFeNiTi 0.1 HEA shows balanced mechanical performance at a wide temperature range (−160 to 800 °C).