Hot Deformation Behavior and Microstructural Evolution of Wire-Arc Additively Fabricated Inconel 718 Superalloy

The hybridization of additive manufacturing techniques with conventional forming processes offers significant reduction in production cost, time, and material wastage to produce near-net shaped components with refined microstructure and desired properties comparable to its wrought counterparts. In this work, the thermomechanical behavior and microstructural evolution of heat-treated wire-arc additively manufactured Inconel 718 parts were investigated using a Gleeble® 3500 physical simulator at different strain rates and temperatures. The results showed that the serrated yielding and flow stress behavior were independent on the sample orientation under the same deformation conditions. The serration behavior was observed to be more sensitive to the applied deformation temperatures than that of strain rates, whereas the opposite was found to be true in case of flow stress (mechanical properties) behavior. The uniformity of dynamically recrystallized (DRX) microstructure was intricately related to the orientation of columnar grains and processing parameters. The evolution of a near-complete DRX structure was more favorable under low flow stress conditions if the deformation direction was aligned perpendicular to the long axis of columnar grains. The nucleation and growth of weakly textured DRX microstructure were characteristic of strain-induced grain boundary migration as a result of the bulging of migrating grain boundaries.