| Abstract Scope |
In this work, we investigated the deformation behavior of heat-treated Inconel 718 using two different heat-treatment cycles i.e., solution treated, double-aged with delta precipitation. Uniaxial tensile tests at three different temperatures i.e., RT, 650◦C, and 750◦C and short term creep rupture tests at two different temperatures i.e., 650◦C, and 750◦C with different constant stress-levels (70 to 90% of yield strength) were performed to comprehend structure-property correlation for Inconel 718. Compared to solution treated sample, double-aged sample promoting the formation of γ′′, γ′ imparted significant boost to yield strength and hardening behavior with substantial reduction in ductility. Temperature dependence of these aged conditions were also observed to be normal where yield strength and ductility reduced with increasing temperature. Temperature dependent deformation behavior of solution treated Inconel 718 is found to be very interesting where we observed increased yield strength with increasing temperature (also known as Yield Stress Anomaly i.e., YSA) and significant reduction in ductility.
Extensive microstructural characterization demonstrate that stress assisted accelerated aging of γ′′ at lower than usual aging temperature and time and extensive γ′′→δ transformations might be the primary driver for the observed behavior of solution treated Inconel 718. However, these transformations does not improve creep rupture life at high temperature and high stress condition. Understanding tensile and creep mechanisms at elevated temperatures and precise control over stress assisted aging and γ′′→δ transformations could be a potential pathway for designing temperature resistant Inconel 718. |