Microstructure and magnetic properties evolution of Al/CoCrFeNi nanocrystalline high-entropy alloy composite

A systematic microstructure-oriented magnetic property investigation for Al/CoCrFeNi nanocrystalline high-entropy alloys composite (nc-HEAC) is presented. In the initial state, the Al/CoCrFeNi nc-HEAC is composed of face-centered cubic (FCC)-Al, FCC-CoCrFeNi and hexagonal close-packed (HCP)-CoNi phases. High energy synchrotron radiation X-ray diffraction and high-resolution transmission electron microscopy were used to reveal the relationship between microstructure evolution and magnetic mechanism of Al/CoCrFeNi nc-HEAC during heat treatment. At low-temperature annealing stage, the magnetic properties are mainly contributed by the HCP-CoNi phase. With the increase of temperature, the diffusion-induced phase transition process including the transformation of AlCoCrFeNi HEA from FCC to BCC structure and the growth of B2 phase plays a dominant role in the magnetic properties. It was found that the magnetic properties can be effectively regulated through the control of the thermal diffusion process. The nano dual-phase thermal diffusion-induced phase transition behavior of nanocomposites prepared based on laser-IGC technology provides guidance for the diffusion process and microstructure evolution of two phases in composites. Graphical abstract