High-entropy CoCrFeMnNi/B2 structure aluminide-laminated composites with enhanced mechanical properties

Abstract

CoCrFeMnNi-based high-entropy/B2 structure aluminide-laminated composites were produced via the hot pressing diffusion sintering method at 1000 ℃. The results revealed that the aluminide structure layer based on the Al13(Cr, Mn, Fe, Co, Ni)4 phase first transforms into Al8(Cr, Mn, Fe, Co, Ni)5 phases with a trigonal crystal structure and then gradually transitions into Al(Cr, Mn, Fe, Co, Ni) phases with a B2 cubic crystal structure under high-temperature annealing. During high-temperature annealing, the elements Ni, Co, and Fe exhibit higher diffusion rates and diffusion amounts in the aluminide layer. The transformation of the aluminide layer is mainly influenced by the diffusion behavior of these elements. The absence of an oxidation interface barrier during high-temperature annealing results in multiple diffusion mechanisms, leading to the predominance of lattice diffusion and interface diffusion, which control the growth kinetic of the Al(Cr, Mn, Fe, Co, Ni) phase layer. The hardness indentation of the B2-Al(Cr, Mn, Fe, Co, Ni) phases, obtained by high-temperature annealing, shows no cracks and exhibits a multi-slip system characteristic of ductile aluminum compounds. This ductile behavior helps to reduce the deformation resistance in the hard and brittle layer and decreases the likelihood of delamination failure during plastic deformation. The bending strength of high-entropy/aluminide-layered (HAL) composite materials after high-temperature annealing reaches 1000 MPa, with the main energy dissipation modes being the plastic deformation of ductile layer and fracture of the hard and brittle layer. Dynamic impact failure forms mainly include plastic deformation and delamination, with impact strength and energy consumption reaching 2317 MPa and 4750 J/mm3, respectively. This study provides phase formation sequence and dynamic mechanical properties of High-entropy CoCrFeMnNi/B2 structure aluminide-laminated composites which proved to be a new type of composites with good impact resistance.