An innovative approach for grain refinement in Ni-based superalloys: Modification in the classical delta process through γ pre-aging treatment

In this correspondence, we present an innovative approach to refine the grain size of Inconel 718 superalloy. By adopting this novel strategy, precipitation of a homogeneously distributed delta phase is achieved through a gamma '' -> delta phase transformation. The grain size of the alloy was remarkably reduced from 200 mu m to 5 mu m through isothermal heat treatment and subsequent plastic deformation. As opposed to the preferred nucleation sites in the classical delta process (DP), the delta phase is homogeneously precipitated in the grain interior. At the isothermal deformation stage, the delta phase served as a precursor to instigate complete dynamic recrystallization (grain refinement) of the parent grains. (C) 2019 Elsevier B.V. All rights reserved.