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

Abstract

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.