Eutectoid lamellar structure strengthened ultra-strong Al₁₃Fe₂₉Co₂₉Ni₂₉ high-entropy alloy

Alloys with a lamellar structure exhibit excellent mechanical properties as a large number of interfaces hinder dislocation motion. Here, an ultra-strong Al₁₃Fe₂₉Co₂₉Ni₂₉ high-entropy alloy (HEA) reinforced by a pearlite-like lamellar structure is studied. The results show that the Al₁₃Fe₂₉Co₂₉Ni₂₉ alloy decomposes into submicron lamellar (face-centered cubic (FCC) + L1₂) and (body-centered cubic (BCC) + B2) phases during heat treatment between 560 °C and 600 °C. The layer thickness is determined to decrease with decreasing transformation temperature in the Al₁₃Fe₂₉Co₂₉Ni₂₉ alloy, and it is proportional to the reciprocal of the undercooling of the phase transition. Strengthened by the submicron lamellar structure, the yield strength of the alloy after annealing at 600 °C reaches 1301 MPa with a ductility of 6.1%. In addition, the yield strength increases with the refinement of the lamellar structure, and it follows the classical Hall–Petch relationship. Furthermore, the lamellar FCC and lamellar BCC phases are strengthened by the nanosized L1₂ and B2 phases, respectively. This lamellar-structure-strengthened alloy possesses a higher strength than other metallic nanolaminates with the same layer thickness, such as Cu–Ni, Ti–Al, and Cu–Ag alloys. Thus, it is envisaged that the proposed alloy will be useful for technological applications.