Abstract Inconel 718 is widely used in high-temperature applications and is commonly processed by hot forming, during which its mechanical performance is governed by the evolving microstructure. While microstructure models are typically calibrated under constant strain rate conditions, industrial hot-forming processes often involve transient strain rate histories. This study examines the microstructural response of Inconel 718 to instantaneous strain rate changes at 1120 °C using compression tests and full-field simulations performed with DIGIMU® 5.1. A representative volume element is initialized from experimental grain size distributions. Strain rate increases from 0.1 to 1 s −1 are applied in the hardening ( ε = 0.1, 0.2) and softening regimes ( ε = 0.5), while decreases from 1 to 0.1 s −1 occur at ε = 0.15, 0.3, and 0.6. Strain rate increases cause a temporary suppression of recrystallization. At ε = 0.1, this results in a delay of Δ ε ≈ 0.07 before nucleation resumes. In the softening regime, recrystallization is already underway, the strain rate increase does not fully interrupt the ongoing process but slows its progression and reduces recrystallization. In contrast, early strain rate decreases immediately lower the critical dislocation density, triggering nucleation bursts at ε = 0.15 or promoting growth of recrystallized grains at ε = 0.6. The results highlight that the microstructure does not adapt instantaneously to strain rate changes but requires a strain interval, underlining the need to consider transient effects in process modeling.
Elekyabi et al. (2026) studied this question.