Synergistic effect of rhenium and ruthenium in nickel-based single-crystal superalloys

The microstructures of ternary Ni-Al-Re and quaternary Ni-Al-Re-Ru single-crystal alloys were investigated at atomic and electronic levels to clarify the synergistic effect of Re and Ru in nickel-based singlecrystal superalloys. In the Ni-Al-Re alloy, it was directly observed that Re atom occupied the Al site of gamma' phase. In the Ni-Al-Re-Ru alloy, the mechanisms of Re repartition between gamma and gamma' phases were proposed. In the dendritic cores, high concentrations of Re exceeded the solubility limit of gamma' phase and partitioned to gamma phase, which led to the homogenization. In the interdendritic regions, Ru resulted in the repartitioning of Re to gamma phase which was proved by transmission electron microscopy and first-principles calculations. (C) 2013 Elsevier Ltd. All rights reserved.