Effect of solution temperature on static recrystallization and ductility of Inconel 625 superalloy fabricated by directed energy deposition

Solution treatment is a very important method to modify the microstructure and mechanical properties of additive-manufactured nickel-based superalloy. This study mainly investigated the effect of solution temperature on static recrystallization and ductility of Inconel 625 superalloy fabricated by directed energy deposition (DED). The microstructural results showed that static recrystallization occurred after solution treatment, and as the solution temperature increased, the recrystallization volume fraction in the alloy gradually increased. When the solution temperature reached 1200 °C, static recrystallization occurred more completely. The tensile results indicated that the elongation and strain hardening exponent of Inconel 625 improved with the solution temperature increased, while the yield strength decreased. The deformation behaviors during the tensile process of different samples were obtained by digital image correlation (DIC), and the results showed that the uniform plastic deformation ability was strengthened with the solution temperature increased. In addition, due to the decrease of dislocation density, the yield strength decreased, too. Besides, the increase of strain hardening exponent delayed the appearance of the necking and the dissolution of the Laves phase caused the ductility increasing.