Effect of high-temperature exposure on the microstructure and mechanical properties of the Al5Ti5Co35Ni35Fe20 high-entropy alloy

Effect of high-temperature exposure on the microstructure and mechanical properties of the Al5Ti5Co35Ni35Fe20 High-Entropy Alloy was studied. High-entropy alloys belong to the group of multi-principal element alloys composed of at least five elements with a concentration between 5 and 35 atomic pct. Despite the multicomponent composition, the goal is to achieve a simple solid solution. The alloy was exposed to a temperature range of 650–900°C for 168h (7 days), after hot rolling and air-quenching. After hot rolling the investigated alloy was not fully supersaturated. The application of air cooling caused γ′ precipitation, which was uniformly distributed within the microstructure. High-temperature exposure caused the growth of γ′ particles. At 700°C and higher, additional continuous and discontinuous precipitation of γ′ was observed. Finally, the microstructure of the investigated alloy consisted of γ matrix and three types of γ’ precipitates, i.e. spherical γ′ phases with bimodal distribution within the grains and elongated DP γ′ phases present at the grain boundaries. The highest mechanical properties were obtained after exposure to 650°C, which was caused by γ′ precipitation. Further increase in temperature decreased the mechanical properties.