Abstract:In order to ameliorate microstructure and optimize properties of Inconel 718 alloy, a novel heat treatment method combining high-temperature ultra-short annealing at 980 °C for 1 min with subsequent double aging was proposed. The results showed that ultra-short annealing generated partially recrystallized microstructure and recrystallized nuclei were formed even in deformed grains, which was confirmed by KAM maps. Therefore, high-temperature ultra-short annealing overcame recrystallization barrier, and the subsequent recrystallization process could be completed during aging treatment with relatively low temperature, resulting in the uniformly refined microstructure (~3.59 μm). The 980-1min-aged sample exhibited outstanding tensile properties. The room temperature ultimate strength and total elongation were 1600 MPa and 19%, respectively. The corresponding values of high- temperature (650 °C) tensile tests were ~1350 MPa and ~26%. Consequently, ultra-short annealing can be a promising route to enhance the properties of Inconel 718 alloy.

Key words: Inconel 718 alloy; ultra-high strength; δ precipitates; recrystallization behavior; aging treatment