Effects of yttrium addition on microstructure and mechanical properties of Inconel 718 alloy produced by sub-rapid solidification

Abstract

Abstract In order to improve the mechanical properties of Inconel 718 alloy produced by sub-rapid solidification, the yttrium (Y) element was added during casting. One alloy with 0.1% weight Y content (0.1Y) and a reference alloy without Y addition (0Y) were produced, which involved homogenization, cold rolling, intermediate annealing, and aging treatment. The influences of Y addition on the microstructure and mechanical properties of Inconel 718 alloy were examined. Due to the precipitation of Ni3Y and Ni17Y2 particles, 0.1Y alloy exhibited a refined grain size and a lower recrystallization fraction. The average grain size of 0Y homogenized sample and 0.1Y homogenized sample were about 50.8\xa0μm and 29.5\xa0μm, respectively. Besides, a higher fraction of δ phase precipitated in the 0.1Y annealed sample, including a large amount of granular or short-rod shape δ phases and a small amount of needle-like δ phases. The area fraction of δ phase in the 0.1Y annealed sample was ~10.45%. However, the area fraction of δ phase in the 0Y annealed sample was lower (~7.93%), and needle-like δ phase was hardly observed under this condition. Compared with 0Y alloy, 0.1Y alloy showed better tensile properties. The 0.1Y alloy after aging treatment exhibited an excellent combination of ultimate tensile strength (~1400\xa0MPa), and total elongation (~20%) when deformed at room temperature.