Influence of ?-Phase on the Grain Shape and Mechanical Properties of Inconel 718

Abstract

The present work comparatively studies the thermomechanical processing of mill-annealed, aged, and solution-treated IN718 strips to study the influence of ?-phase precipitates on the grain aspect ratio and the mechanical properties. Prior-treated strips were subjected to thermomechanical processing by cold rolling followed by recrystallization annealing. The processed strips were then mechanically tested and characterized by: hardness measurement, tensile testing, microstructural analysis, electron backscatter diffraction (EBSD) analysis, and x-ray diffraction (XRD) analysis. The results suggest that the recrystallized strips do not show any crystallographic texture, yet possess orthotropic properties along the rolling and transverse directions. The microstructural features correlate well with the mechanical properties, suggesting that the precipitates of ?-phase positively influence the recrystallization kinetics and grain refinement. However, the presence of large fraction of coarse ?-phase precipitates adversely influence the grain aspect ratio and the tensile properties. The study reveals that solution-treated IN718, when subjected to suitable thermomechanical processing, yields a highly refined microstructure with high aspect ratio and superior mechanical properties, especially in the rolling direction. © ASM International 2025.