Effect of 900–1150 °C aging on the microstructure and mechanical properties of a DS casting Ni3Al-base alloy IC6

The effect of high-temperature aging at 900–1150 °C on microstructure and mechanical properties of a recently developed directional-solidification (DS) casting Ni3Al-base alloy has been studied in the present investigation. The microstructure change during aging in the temperature range 900–1150 °C for periods of 25 to 4400 h has been examined by optical microscope, SEM and TEM. The tensile and stress rupture properties of the specimens after aging at 900, 1000 and 1100 °C for periods of 25 to 1000 h have been determined. The experimental results showed that the mechanical properties slowly deteriorated with aging time. The deterioration of properties was attributed to the microstructure changes during aging, which include a volume fraction decrement of the main strengthening phase γ-Ni (Mo) solid solution due to the formation of γ-Ni Mo phase by the reaction of γ → Y-NiMo + γ′, the coalescence and growth of both γ and γ′ phase and a solution-hardening decrease due to the homogenization of Mo distribution in the γ and γ′ phases.