High-throughput additive manufacturing and characterization of CoCrFeNi–AlTi high-entropy alloys

Co-precipitation strengthening of the L1₂ nano-particles along with hard intermetallic phases, including L2₁, B2, σ and η, demonstrates significant potential for the development of advanced CoCrFeNi high-entropy alloys (HEAs) with favorable strength-ductility balances. Understanding the alloying effect of Al and Ti on the formation and stability of these intermetallic phases in the CoCrFeNi HEAs is crucial for efficiently exploring the multi-component space for future alloy designs. In the present work, stepwise compositionally graded CoCrFeNi–AlTi HEAs comprising 35 different compositions were fabricated using high-throughput additive manufacturing (AM) and analyzed through a suite of localized characterization techniques. Our analysis confirmed the existence of two primary solid solution phases, face-centered cubic (FCC) and body-centered cubic (BCC), as well as four distinct intermetallic phases, which include L1₂, L2₁, σ and η. By overlapping the zero phase fraction (ZPF) lines of these phases, the pseudo-ternary phase diagram of the multi-component CoCrFeNi–AlTi system at 800 °C was determined, demonstrating good agreement with the literature results. Furthermore, the composition-dependent microstructural evolution and Vickers hardness (HV) were also established, providing numerous opportunities to design CoCrFeNi–AlTi HEAs with superior microstructure stability and balanced strength-ductility properties for structural applications at elevated temperatures.

Graphical abstract