Analyzing the ‘non-equilibrium state’ of grain boundaries in additively manufactured high-entropy CoCrFeMnNi alloy using tracer diffusion measurements

Additively manufactured (AM) metallic materials contain typically numerous grown-in defects which limit durability and mechanical properties of workpieces. However, the existence and impact of non-equilibrium vacancies and dislocations and especially the state of grain boundaries in AM materials remained completely unexplored. Here we are presenting an ultimate proof of a ‘non-equilibrium state’ of general high-angle grain boundaries in an as-produced AM high-entropy CoCrFeMnNi alloy. A low-temperature annealing treatment relaxes the ‘non-equilibrium’ grain boundary state without invoking grain growth. The ‘non-equilibrium’ state of grain boundaries in AM materials resembles that in severely plastically deformed ones and needs to be taken into account for technological applications. We further report a strong microstructure-induced anisotropy of grain boundary kinetic properties in the AM high-entropy alloy. [Display omitted] •Non-equilibrium GB state is discovered in as-printed additively manufactured (AM) HEA.•AM alloys possess heterogeneous strain distribution with a hierarchical structure.•AM-processed state revealed ultrafast GB diffusivities comparing to those in annealed state.•The non-equilibrium state of GBs relax after low-temperature annealing.•A microstructure-induced anisotropy of GB diffusion in the AM alloy is found.