Condition-driven mechanism transitions: Superplastic deformation and microstructural response of Inconel 718
Year: 2026
Type: article
Abstract: This study aims to elucidate the fundamental superplastic deformation mechanisms and microstructural evolution of a fine-grained Inconel 718 sheet, which is crucial for optimizing its superplastic forming process window. Within the range of 910-970 °C and strain rates of 6×10⁻⁴ to 4×10⁻³ s⁻¹, the alloy exhibits excellent superplasticity, with a maximum strain of 750%, strain rate sensitivity (m) values of 0.33-0.44, and a true activation energy close to that of lattice self-diffusion. The flow stress is governed by the dynamic competition between work hardening (from dislocation multiplication) and flow softening (primarily from dynamic recrystallization and cavity nucleation). The δ phase (Ni₃Nb) evolution exerts a dual influence on flow stress, acting as a strengthener via pinning effects initially, but inducing a softening effect later as its dissolution reduces pinning and enhances boundary mobility. Moreover, grain boundary sliding (GBS) serves as the dominant strain-producing mechanism, which is accommodated by intragranular dislocation activity, with the specific mode being determined by the obstacle grain size. Dislocation glide predominates when accommodating GBS for small obstacle grains, while sub-grain boundary formation becomes the prevailing mode around large obstacle grains. A decrease in temperature or an increase in strain rate promotes a transition in the accommodation mechanism from dislocation glide to sub-grain boundary formation. This work provides a profound understanding of the relationship between deformation conditions and microstructural evolution, ultimately revealing the condition-dependent transitions in deformation mechanisms governing superplasticity of Inconel 718.
Institutions: Shenyang University of Technology, Northeastern University
Language: English
Subfield: Mechanics of Materials
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,640
Award: G8804301875
OpenAlex ID: W7140826507