Comparison of Different Characterization Strategies for the Parametrization of Post-dynamic Recrystallization of Inconel 718 in a Full-Field Model

Microstructural modelling offers the possibility of reducing the experimental effort and accelerating development processes. Here, full-field models are of increasing interest as they give an improved physical representation of the metallurgical mechanisms as well as a wider range of validity compared to simpler models. However, to be able to model microstructural evolution properly using a full-field model, the basic mechanisms of grain growth and recrystallization (RX) need to be characterized experimentally before identifying the model parameters. An important mechanism here is the post-dynamic recrystallization (PDRX), i.e., the evolution of microstructure after deformation at upheld elevated temperatures. Different characterization approaches like the stress relaxation method, interrupted compression or torsion tests have been used for PDRX investigations. However, no investigation on the influence of the different characterization methods on the final material parameters have been conducted. In this study, two characterization methods are used to investigate the PDRX of Inconel 718 in the commercial software DIGIMU®. Firstly, stress relaxation tests are conducted in the super-solvus area. Here a strain is applied before the onset of dynamic recrystallization (DRX) and kept constant during the test. The RX-kinetic is derived from interrupted samples during the holding time. Based on the RX-kinetics, a first set of model parameters is identified. Secondly, compression tests are interrupted at different DRX-fractions and subsequently held at the test temperatures to analyze further development in the post-dynamic regime. The previously identified parameters are used to simulate the microstructural evolution for the second set of experiments. Results show good agreement of the RX-kinetics in both cases. Deviations in the average grain size are identified for the interrupted compression test at 1120 ℃ while a very good agreement is reached for 1020 ℃ and 1070 ℃. The results suggest that it is possible to identify the PDRX parameters based on a testing method consisting of SRX and use them for MDRX simulations.