Investigation on hot workability characteristics of Inconel 625 superalloy using processing maps

Guo, Shengli; Li, Defu; Guo, Qigao; Wu, Zhigang; Haijian, Peng; Hu, Jie

doi:10.1007/s10853-012-6488-x

Cited by 38 publications

(16 citation statements)

References 26 publications

(30 reference statements)

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“…That it to say, numerous researchers have identified the deformation temperature to have a critical influence on the recrystallization behaviour of Alloy 625 [29,30,31,32], leading to potential significant disparities in the recrystallisation fraction throughout the thickness of products due to thermal gradients [33]. It is, therefore, likely that the lower temperature experienced by the surface adjacent region of the Alloy 625 forging ultimately 70 analysed in this work fell below (owing to both convective/radiative cooling and conduction with the forging press) that which would have been sufficient (depending on the strain rate)…”

Section: Grain Structurementioning

confidence: 99%

Grain coarsening behaviour of solution annealed Alloy 625 between 600–800 °C

Moore

Taylor

Tracy

et al. 2017

Materials Science and Engineering: A

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As with all alloys, the grain structure of the nickel-base superalloy 625 has a significant impact on its mechanical properties. Predictability of the grain structure evolution in this material is particularly pertinent because it is prone to inter-metallic precipitate formation both during manufacture and long term or high temperature service. To this end, analysis has been performed on the grain structure of Alloy 625 aged isothermally at temperatures between 600-800 • C for times up to 3000 hours. Fits made according to the classical Arrhenius equation describing normal grain growth yield an average value for the activation energy of a somewhat inhomogeneous grain structure above 700 • C of 108.3±6.6 kJ mol −1 and 46.6±12.2 kJ mol −1 below 650 • C. Linear extrapolation between 650-700 • C produces a significantly higher value of 527.7 ± 23.1 kJ mol −1 . This result is ultimately a consequence of a high driving force, solute-impeded grain boundary migration process operating within the alloy.Comparison of the high and low temperature values with the activation energy for volume self-diffusion and grain boundary diffusion identifies the latter as the principle governing mechanism for grain growth in both instances. A decrease in the value of the time exponent (n) at higher temperatures despite a reduction in solute drag is attributable to the Zener pinning imposed by grain boundary M 6 C and M 23 C 6 particles identified from Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDXS) analysis.Vickers hardness results show the dominance of intermetallic intragranular precipitates in 1 the governance of the mechanical properties of the material with grain coarsening being accompanied by a significant increase in hardness. Furthermore, the lack of any correlation with grain growth behaviour indicates these phases have no significant effect on the grain evolution of the material.

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Section: Grain Structurementioning

confidence: 99%

Grain coarsening behaviour of solution annealed Alloy 625 between 600–800 °C

Moore

Taylor

Tracy

et al. 2017

Materials Science and Engineering: A

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“…Hot flow behavior exhibits hardening and softening characteristics accompanied by various metallurgical mechanisms like work hardening (WH), dynamic recovery (DRV), dynamic recrystallization (DRX), static recrystallization (SRX), static recovery (SRV), metadynamic recrystallization (MDRX), and superplastic grain growth resulting in complex microstructural evolution [1][2][3][4][5][6][7]. In view of this, optimizing hot working process is of prime importance for metal working industries.…”

Section: Introductionmentioning

confidence: 99%

Constitutive modeling for predicting peak stress characteristics during hot deformation of hot isostatically processed nickel-base superalloy

et al. 2015

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Hot flow behavior of hot isostatically processed experimental nickel-based superalloy is investigated over temperature and strain rate ranging from 1000-1200°C and 0.001-1 s -1 , respectively by carrying out constant true strain rate isothermal compression tests up to true strain of 0.69. True stress-true strain curves corrected for adiabatic temperature rise exhibited rapid strain hardening followed by flow softening behavior irrespective of temperature and strain rate regimes investigated, although anomalous flow behavior is observed at 1200°C. Variation of peak flow stress with temperature is corroborated to the microstructural changes pertaining to the morphology and relative volume fraction of the phases present. From the experimental results, constitutive model incorporating the effects of strain rate, strain, and temperature is established to describe the hot flow behavior of investigated alloy. Dependence of peak flow stress on strain rate and temperature described by Zener-Hollomon (Z) parameter indicated increase in peak flow stress with Z. Additionally Cingara-Queen equation is employed to predict flow curve up to peak stress. The reliability of developed constitutive models is validated statistically and the results indicate reasonable agreement with experimental findings.

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“…The solidus temperature was calculated as 1137 • C according to the Scheil module in Thermo-Calc [32]. The flow stress for the annealed state of the material was compiled from stress-strain curves from various sources [33][34][35], as indicated in Table 2. The flow stress was tabulated versus plastic strain and temperature, which was used to interpolate flow stress and hardening of the material.…”

Section: Materials Modelsmentioning

confidence: 99%

History Reduction by Lumping for Time-Efficient Simulation of Additive Manufacturing

Malmelöv

Lundbäck

Lindgren

2019

Metals

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Additive manufacturing is the process by which material is added layer by layer. In most cases, many layers are added, and the passes are lengthy relative to their thicknesses and widths. This makes finite element simulations of the process computationally demanding owing to the short time steps and large number of elements. The classical lumping approach in computational welding mechanics, popular in the 80s, is therefore, of renewed interest and is evaluated in this work. The method of lumping means that welds are merged. This allows fewer time steps and a coarser mesh. It was found that the computation time can be reduced considerably, with retained accuracy for the resulting temperatures and deformations. The residual stresses become, to a certain degree, smaller. The simulations were validated against a directed energy deposition (DED) experiment with alloy 625.a thermo-mechanical model where whole layers were added simultaneously when a part with 50 layers was built. This model was validated against an experiment. Keller et al. [17,18] described a model where several layers were added simultaneously. With their model they were able to predict deformation and residual stresses at the macroscopic level. In the current work the temperature and deformation evolution is studied when the passes are added transiently, and only lumped in the build direction. To the authors' knowledge there is no publication where the approach has been used in this way. The inherent strain method is another approach for fast prediction of the resulting deformation and residual stress in AM processes [19,20]. The method was first proposed for welding by Ueda and coworkers [21][22][23]. Li et al. [24,25] used the inherent strain approach, but instead of using strain, a residual stress tensor is added to each layer in the mechanical macro-scale model. The simulation was performed with a multi-scale model in three different scales. A micro-scale model was used to predict an equivalent heat source, which was the input to the meso-scale model. Because the AM process is very fast, it was assumed that the heat could be added to the whole layer simultaneously. In the thermo-mechanical meso-scale model, a residual stress tensor from one added layer was calculated.Finally, the mechanical model on the macro-scale was computed, wherein the material was added layer by layer and the pre-determined residual stress tensor was applied on each added layer. The drawback with the inherent strain method is that it often requires calibration. The inherent strains are in general sensitive to changes in the boundary conditions.The main aim of this work was to study the method lumping of welds, described above, and evaluate the error introduced in the modeling and the achieved reduction in computation time for the simulations. A detailed thermo-mechanical FE model was validated with in situ temperature and displacement measurements for directed energy deposition (DED) with alloy 625. All experimental data and results that are used for comparison with the sim...

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Investigation on hot workability characteristics of Inconel 625 superalloy using processing maps

Cited by 38 publications

References 26 publications

Grain coarsening behaviour of solution annealed Alloy 625 between 600–800 °C

Grain coarsening behaviour of solution annealed Alloy 625 between 600–800 °C

Constitutive modeling for predicting peak stress characteristics during hot deformation of hot isostatically processed nickel-base superalloy

History Reduction by Lumping for Time-Efficient Simulation of Additive Manufacturing

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