An innovative constitutive material model for predicting high temperature flow behaviour of inconel 625 alloy

Abstract

Inconel 625 nickel alloy with its attractive high-temperature strength, excellent corrosion and oxidation resistance is mainly used for critical applications in demanding environments, in both as-cast and wrought conditions. Hot processing of this alloy is crucial for achieving its tailored mechanical properties due to the significant variation in microstructural changes with varying process parameters like temperature, strain, and strain rate. In this study, isothermal hot compression tests were carried out at temperatures ranging from 900 to 1100 °C, and under strain rates ranging from 0.01 to 1 s−1. The flow curves revealed three stages of deformation, including a substantial work-hardening stage followed by dynamic recovery and flow softening. Microstructural observations showed the occurrence of discontinuous dynamic recrystallisation (DDRX) as the dominant recrystallisation mechanism during the flow softening. Microstructural analysis suggested that the DRX was more sensitive to the test temperature as compared to the strain rate. An innovative material's constitutive model was developed, by combining Johnson–Cook (JC) and Avrami approaches, to predict work-hardening, dynamic recovery, and flow softening stages of deformation. The predicted flow behavior was in a good agreement with the experimentally measured data. The developed material model was integrated into DEFORM® 3D finite element (FE) simulation software as a user subroutine for the prediction of deformation behaviour in a double truncated cone (DTC) sample. Comparison between the experimentally measured data and the results of FE simulation on the DTC sample showed a very good convergence, indicating the suitability of the proposed material’s constitutive model for large scale simulations. Graphical Abstract

Analysis of Hot Tensile Fracture and Flow Behaviors of Inconel 625 Superalloy

“…This is because DRX and DRV are still not enough to compete with WH. Upon surpassing the threshold for DRX, the dislocations annihilate (without recombining) toward the newly formed DRX grain boundaries [ 32 ]. Consequently, the rate of tensile stress diminishes, resulting in peak stress.…”

INCONEL® Alloy Machining and Tool Wear Finite Element Analysis Assessment: An Extended Review

“…The value of C is derived through a linear regression model using different . ε values obtained from the SHPB test [33].…”

“…The JC model can be reorganised to determine the m parameter, overlooking . ε strengthening effects, as demonstrated in Equation (4) [33]. Estimating m involves performing the push-rod dilatometer test under ASTM E 228-17 [34], analysing the linear thermal expansion, and evaluating m in Equation (4) using the linear regression model graph [35].…”

“…Murugesan and Jung [15] formulated surrogate models based on constitutive relations, and the model constants were estimated using experimental data. Souza, et al [33] successfully predicted the behaviour of INCONEL ® 625 by integrating the JC and Avrami models [40], as demonstrated in Equation ( 5), for the resulting stress (s JC + A ):…”

Optimisation of sample geometry for thermo‐mechanical testing of precipitation hardenable nickel‐based superalloys with an ETMT machine

“…Therefore, it can be seen that the correction applied is predominantly to address the strain outside the 2 mm gauge length in the centre of the sample. Constitutive models have been used to predict the flow stress at elevated temperatures [27][28][29][30][31] ; however, it is well known that a constitutive model is heavily dependent on the material characteristics (i.e., microstructure), the strain rate and the temperature at which the tests were carried out. Therefore, it is assumed that further work would need to be carried out to determine the robustness of Equation ( 3), to see if it is representative of all precipitation hardened materials, and for what temperature and strain rate regimes.…”