Effect of multiscale heterogeneous microstructural evolution on mechanical and corrosion properties of (CrCoNi)94Al3Ti3 medium-entropy alloy manufactured by laser powder-bed fusion

This study comprehensively investigates the microstructure, mechanical properties, and corrosion behavior of a laser powder-bed fusion (CrCoNi) 94 Al 3 Ti 3 medium-entropy alloy in the printed state (without heat treatment) and two different heat-treatment processes (direct aging and solution aging). Following direct aging, the as-printed sample displayed numerous fine annealing twins along the grain boundaries, with minimal alteration in the segregation of Ti at the substructure boundaries. Conversely, the solution-aged sample showed multiscale annealing twins, a high density of L1 2 precipitates, and the elimination of Ti elemental segregation. Mechanical-property evaluations indicated that the strength of the sample significantly increased, but the ductility decreased after direct aging for 2 h, whereas the sample solution aged for 2 h achieved a good balance between strength and ductility (yield strength: 1053.3 MPa, ultimate tensile strength: 1396.7 MPa, total strain: 24.2%). The deformation mechanisms of the direct-aged samples were cross-slip bands, stacking faults, and deformation twinning, whereas the main features of the solution-aged sample were the formation of Lomer–Cottrell locks and extensive stacking faults and deformation twins. Compared with both the as-printed and direct-aged samples, the solution-aged sample exhibited superior general corrosion resistance. This research offers significant insights into heat-treatment strategies aimed at improving the additive-manufacturing performance of medium-entropy alloy components.