Effect of high temperature heat treatment on microstructure and properties of FeCoCrNiAl high-entropy alloy laser cladding layer

Abstract

Here, the heat treatment for FeCoCrNiAl high-entropy alloy (HEA) laser cladding (LC) layer was given at a temperature which is higher than that of the first phase transition. The effects of heat treatment on the phase transition, microstructure and mechanical properties of the LC-ed FeCoCrNiAl were studied. Meanwhile, the LC-ed sample was compared with the casting specimen. The results showed that the cladding layer had lower activation energy of phase transformation, and it had higher proportion of Fe element because of the dilution of the matrix metal, which promoted the formation of face-centered cubic (FCC) phase. Then more FCC phase structures precipitated in the cladding layer after heat treatment. However, the formation of FCC phase did not change the texture characteristics of the cladding layer. The differences in physical properties, slip system, Burgers vector and dislocation types between the two phases, as well as the serious atomic disarrangement at the two-phase interface, caused a significant increase of dislocation density. The mechanical properties of the FeCoCrNiAl-HEA were improved by the the presence of proper amount of FCC phase combined with fine grains strengthening and dislocation strengthening. Nevertheless, the excess amount of FCC phase promoted plastic deformation and weakened the strengthening effects of dislocation and fine grain strengthening. • Alloying elements and activation energies promoted phase transformations under thermal action. • Solid phase transition under heat treatment did not change the grain growth orientation in coating. • Variations in physical properties between two phases promoted the existance of dislocations. • Dislocations, fine grains and phase proportions influenced mechanical properties of FeCoCrNiAl.