Microstructural simulation of nickel base alloy Incone* 718 in production of turbine discs

Brand, A.J.; Karhausen, Kai F.; Kopp, Reiner

doi:10.1179/mst.1996.12.11.963

Cited by 76 publications

(30 citation statements)

References 7 publications

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“…The volume fraction dynamically recrystallised curves have been shifted along the time axis such that the volume fraction recrystallised just before the critical strain is reached are aligned. These graphs prove that strain rate affects recrystallisation kinetics in a way more complicated than by just altering the time over which dynamic recrystallisation can Figure 3, agree with Brand and coworkers [3] and Camus et al [4] who have explained the increased rate in meta-dynamic recrystallisation after deformation at high strain rates as a result of adiabatic heating. The observation that a shorter time before the onset of meta-dynamic recrystallisation resulted from an increase in strain rate and an increase in strain made by Sun and Hawbolt [2] has not been validated in this work as post deformation hold periods were not subjected to samples deformed to strains other than 0·82, however, this observation would fit in both with the experimental results shown here, and the theory already discussed as an increase in strain rate or strain would increase the dislocation density within the material, increasing the probability of nucleation events occurring.…”

Section: Influence Of Strain Ratesupporting

confidence: 77%

The Dynamic and Metadynamic Recrystallisation of IN 718

Guest¹,

Tin²

2005

Superalloys 718, 625, 706 and Various Derivatives (2005)

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The recrystallisation behaviour of IN 718 has been analysed using a Gleeble 1500 thermomechanical simulator. The use of a rapid water quenching system immediately after the compression test has resulted in the ability to separate dynamic behaviour from meta-dynamic. The rate of dynamic recrystallisation has been found to be proportional to temperature and strain, but inversely proportional to strain rate. The nucleation rate of recrystallised grains during deformation has been found to be directly linked to strain rate and temperature. The rate of meta-dynamic recrystallisation appears to be directly proportional to temperature and strain rate, but no new nucleation events were observed after the end of deformation MethodsMaterial was supplied for the experiments by Firth Rixson Forgings Ltd in the form of a forged and rolled billet of IN 718. Cylindrical samples of height 12 mm and diameter 8 mm were spark eroded from the billet and deformed using a Gleeble 1500 thermomechanical simulator.Initially, the effects of temperature and strain rate on dynamic recrystallisation were investigated. Samples were deformed at a temperature of either 980 • C or 1040 • C to predefined strains of 0·09, 0·18, 0·29, 0·41, 0·53, 0·67, and 0·82 at a set die velocity resulting in average strain rates of 0·01, 0·1, 0·45, and 1·1 s −1 followed by an immediate water quench. To investigate meta-dynamic recrystallisation, samples deformed to a strain of 0·82 were also held at the test temperature for times ranging from 1 second to 10 minutes before undergoing a water quench. Each experiment begins with a linear heat-up to test temperature over 2 minutes and then a hold for 1 minute. The tests were followed by a water quench designed to reduce the temperature of the sample as quickly as possible. Figure 1 shows the temperature profile of a typical test, showing the heat-up, hold, and quench. Thermal data is plotted for both the centre of the sample, and either end, measured using thermocouples welded to the sample. It can be seen that, although a large thermal gradient exists during the heating stage, after a 1 minute hold period, the sample is at a uniform temperature. Referring to Figure 1 (b), it can be seen that the water quench stage lowers the temperature of the specimen extremely rapidly. It takes only 1·1 seconds for the sample to reach 200 • C, and less than 0·2 seconds for the centre of the sample to fall below 800 • C (a temperature below which the rate of recrystallisation is almost zero).

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Section: Influence Of Strain Ratesupporting

confidence: 77%

The Dynamic and Metadynamic Recrystallisation of IN 718

Guest¹,

Tin²

2005

Superalloys 718, 625, 706 and Various Derivatives (2005)

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“…1 using both peak and steady-state stresses, are presented in Table 3. An activation energy of 430 kJ mol -1 for hot-working of solutiontreated IN718 (Type I microstructure) is in good agreement with values derived for the same material in the literature, 390-440 kJ mol -1 [8][9][10][11]. Higher values of Q for the Type II and Type III materials, as listed in Table 2, can be attributed to the presence of d precipitates; second-phase particles are known to affect the measured hot-working activation energy in steels [22] and two-phase titanium alloys [23].…”

Section: Deformation Behaviorsupporting

confidence: 75%

“…2a, b. The overall behavior is in broad agreement with that usually observed for IN718: A distinct peak stress, tending to be more pronounced at higher strain rates, is followed by significant post-peak flow softening that is generally attributed to recrystallization and/or adiabatic heating [6][7][8][9][10]. Since all the flow curves presented here have been corrected for the effect of deformation heating, the observed flow softening must, in this case, be due to the evolving microstructural state of the material.…”

Section: Deformation Behaviorsupporting

confidence: 71%

“…Significant research has been directed toward characterizing the precipitation and dissolution kinetics of the d phase in IN718 during heat treatment and aging, e.g., [1][2][3][4][5], and several experimental investigations have explored recrystallization associated with high-temperature compressive flow in solution-treated material, e.g., [6][7][8][9][10], but there has been rather less focus on the specific role of d precipitates during hot deformation. However, it is known that prior aging in the d stability field can have a significant effect on stress-strain response [11,12] and recent studies have highlighted the complexity of the mechanisms involved, including dynamic dissolution and reprecipitation [13], sub-grain formation [14], and platelet spheroidization [15].…”

Section: Introductionmentioning

confidence: 99%

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Hot Forging of IN718 with Solution-Treated and Delta-Containing Initial Microstructures

Lalvani

Brooks

2016

Metallogr. Microstruct. Anal.

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A systematic study of the effect of d phase precipitate morphology on the hot deformation behavior and microstructural evolution in nickel superalloy Inconel 718 is presented. Isothermal compression tests at fixed nominal strain rates and temperatures relevant to industrial forging (0.001-0.3 s -1 and 990-1040°C) were used. Three distinct initial microstructures have been examined: (I) solution treated, (II) a microstructure with finely dispersed particulate d precipitates, and (III) a microstructure containing dense network of intragranular and grain boundary d platelets. The peak flow stress associated with these various microstructures has been rationalized using a single, temperature-compensated power law. This clearly demonstrates opposition of the external applied stress by an internal back stress related to the initial d phase morphology and apparent delta solvus temperature. Post-peak flow softening is attributed to dynamic recrystallization, aided by the dissolution of finer precipitates in material containing particulate d phase, and to a certain degree of mechanical grain refinement caused by distortion and offsetting of grain segments where a dense d-platelet structure exists.

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“…[1][2][3][4][5][6][7][8][9][10][11][12]), they either fall into the category of being too simplistic and producing only an average grain size and approximate volume fraction recrystallised, or are far too complicated and too computationaly intensive to be used on a daily basis by process engineers. A model is required, therefore, that can be run within a commercially available finite element package, or in tandem with one, that will deliver detailed results, run in a reasonable time, and be simple to use.…”

Section: Introductionmentioning

confidence: 99%

Modelling Microstructural Transformations of Nickel Base Superalloy in 718 During Hot Deformation

Guest¹,

Tin

2005

Superalloys 718, 625, 706 and Various Derivatives (2005)

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A new Inconel 718 microstructural evolution model that works in tandem with finite element software is described, and is then used to predict the microstructure during the production of a typical two-stage forging route. The model works by grouping similar grains into grainsets and predicting the dislocation density within these grainsets during thermomechanical processing. The model is shown to accurately predict both the grain size and presence of δ precipitates during the processing route, and displays results both numerically and graphically.

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Microstructural simulation of nickel base alloy Incone* 718 in production of turbine discs

Cited by 76 publications

References 7 publications

The Dynamic and Metadynamic Recrystallisation of IN 718

The Dynamic and Metadynamic Recrystallisation of IN 718

Hot Forging of IN718 with Solution-Treated and Delta-Containing Initial Microstructures

Modelling Microstructural Transformations of Nickel Base Superalloy in 718 During Hot Deformation

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