Microstructure and Mechanical Properties of Precipitate Strengthened High Entropy Alloy Al(10)Co(25)Cr(8)Fe(15)Ni(36)Ti(6) with Additions of Hafnium and Molybdenum

High entropy or compositionally complex alloys provide opportunities for optimization towards new high-temperature materials. Improvements in the equiatomic alloy Al(17)Co(17)Cr(17)Cu(17)Fe(17)Ni(17) (at.%) led to the base alloy for this work with the chemical composition Al(10)Co(25)Cr(8)Fe(15)Ni(36)Ti(6) (at.%). Characterization of the beneficial particle-strengthened microstructure by scanning electron microscopy (SEM) and observation of good mechanical properties at elevated temperatures arose the need of accomplishing further optimization steps. For this purpose, the refractory metals hafnium and molybdenum were added in small amounts (0.5 and 1.0 at.% respectively) because of their well-known positive effects on mechanical properties of Ni-based superalloys. By correlation of microstructural examinations using SEM with tensile tests in the temperature range of room temperature up to 900 °C, conclusions could be drawn for further optimization steps.