February 2026 Volume 8

FORGING RESEARCH

Figure 5: (a) Representation of a grain with local curvatures and an explicit neighborhood in a DIGIMU® simulation, compared with (b) the averaging of curvatures and the statistical neighborhood in NHM. Model Validation Metrics Quantitative comparison between NHM and DIGIMU® yielded: grain size prediction accuracy of ±10% for majority of conditions, recrystallization fraction correlation with R² > 0.85, kinetics timing within 15% for transformation completion times, and SPP pinning effectiveness qualitatively consistent and quantitatively within 20%.

Figure 4: Microstructural results (left: recrystallized fraction, right: average grain diameter) interpolated from the sensors on the cutting plane using DynamiX (top) and the JMAK model integrated in FORGE® (bottom). Dynamic Recrystallization Predictions Comprehensive simulations were conducted across three temperature levels (980°C, 1050°C, 1120°C) and multiple strain rates. Key findings include: High Zener-Hollomon parameter conditions (high strain rates/ low temperatures): NHM predictions showed excellent agreement with DIGIMU® results, with average grain size predictions within 5% deviation and recrystallization kinetics accurately captured. Low Zener-Hollomon parameter conditions (low strain rates/ high temperatures): Increased divergence between mean-field and full-field predictions, with NHM showing tendency toward narrower grain size distributions. This limitation was attributed to insufficient microstructural classes under these conditions. Recrystallization Kinetics Evolution At 1050°C with 0.1 s -1 strain rate: • 5 seconds (0.5 strain): DIGIMU® predicted 12% recrystallization vs. 25% for NHM • 10 seconds (1.0 strain): Recrystallized fractions converged between models • 20 seconds (2.0 strain): Final grain size distributions broadly similar, with NHM showing slight over-concentration around mean values Second-Phase Particle Effects Investigation of partial DRX with PDRX at 980°C revealed: • Initial stages (0-12 seconds): No significant SPP influence observed during active DRX • PDRX phase: Clear grain growth retardation upon reaching 100% recrystallization • Final microstructure: Mean equivalent diameter limited to below 20 μ m with 0.5% SPP fraction • Parametric sensitivity: Consistent pinning effects observed across varying SPP fractions The Smith-Zener pinning mechanism was successfully captured by both NHM and DIGIMU®, with qualitative agreement in growth kinetics reduction.

Figure 6: Comparison of grain size results during grain growth, obtained with NHM (red curves) and DIGIMU® (green curves) at different temperatures.

Applications Industrial Process Optimization The validated modeling framework enables multiple industrial applications: Forging Process Design: The rapid computation times of NHM coupled with DynamiX allow engineers to optimize multi-pass forging sequences for Inconel 718 components. The tool can predict final grain size distributions across complex geometries, enabling design of thermomechanical processing routes that achieve target microstructures. Quality Control and Certification: The ability to predict microstructural evolution provides a virtual certification capability, reducing the need for destructive testing while ensuring compliance with aerospace specifications for grain size and uniformity. Alloy Development: The framework accelerates development of new nickel-based superalloys by enabling rapid screening of composition-processing-microstructure relationships without extensive experimental trials.

FIA MAGAZINE | FEBRUARY 2026 68