A novel approach to investigate delta phase precipitation in cold-rolled 718 alloys

Low, Zi Kang; Chaise, Thibaut; Bardel, Didier; Cazottes, Sophie; Chaudet, Philippe; Perez, Michel; Nélias, Daniel

doi:10.1016/j.actamat.2018.06.005

Cited by 23 publications

(6 citation statements)

References 38 publications

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“…Alternatively, several attempts have been made to develop modeling-and-simulation techniques which treat the detailed mechanisms of nucleation, growth, and coarsening of the precipitate phases in 718 (as well as related alloys such as 625 and 718Plus). [24][25][26][27][28] These approaches require large amounts of thermodynamic and kinetic input data and often include simplifying assumptions or calibration/tuning methods whose bases need to be justified. Despite such shortcomings, the tools provide great promise for investigating the effect of changes in processing parameters on heat-treatment response, microstructure variability in large forgings, etc.…”

Section: Introductionmentioning

confidence: 99%

In-Situ Determination of Precipitation Kinetics During Heat Treatment of Superalloy 718

Cormier

Gadaud

Czaplicki

et al. 2020

Metall Mater Trans A

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Two in-situ test techniques were used to obtain insight into the isothermal precipitation kinetics of c¢¢ and c¢ in superalloy 718. The first method consisted of measurements of Young's modulus using a dynamic-resonance method (DRM), and the other comprised determination of the evolution of the lattice parameter of the c-matrix phase via neutron diffraction. For both techniques, solution-treated-and-water-quenched samples were heated to a nominal test temperature of 923 K, 953 K, 1013 K, or 1053 K and held for a time of~5 to 50 hours, at the end of which a near-steady condition in terms of an apparently-constant modulus/lattice parameter had been achieved. The observations from each test technique suggested sequential periods of rapid initial increase in volume fraction followed by a gradually-decreasing rate of change. The data were converted to transformed fraction as a function of time and interpreted in terms of phenomenological (JMAK) and mechanistic (nucleation-and-growth) models. From the former approach, Avrami exponents which decreased from approximately unity at the lower two temperatures to~0.5 at the highest temperature, were deduced. The transformed fraction-versus-time behaviors were well replicated using fast-acting numerical simulations based on the mechanistic model. These simulations highlighted the competition between nucleation and growth in determining overall transformation kinetics.

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Section: Introductionmentioning

confidence: 99%

In-Situ Determination of Precipitation Kinetics During Heat Treatment of Superalloy 718

Cormier

Gadaud

Czaplicki

et al. 2020

Metall Mater Trans A

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“…Compared to the numerous modeling efforts devoted to PM strengthened superalloys and selected other superalloys (e.g., 625 [27] and ATI 718Plus [28] ), the simulation of aging heat treatments for cast-and-wrought 718 has received relatively-little attention [29][30][31][32] . Such limited work may be ascribed to challenges associated with the complex nature of the phase equilibria between the  matrix,  and  precipitates, and  phase (at high temperatures) and the scarcity of kinetic data (i.e., diffusivities/mobilities) and other important input material properties (e.g., interface energies, bulk free energies of formation) required for such simulations.…”

mentioning

confidence: 99%

A Fast-Acting Method for Simulating Precipitation During Heat Treatment of Superalloy 718

Semiatin

Tiley

Zhang

et al. 2021

Metall Mater Trans A

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A fast-acting, mean-field method for simulating precipitation of the  and  phases during aging of superalloy 718 following super--solvus solution treatment was formulated and validated using observations in the literature. The approach assumed classical (homogeneous) nucleation and diffusion-controlled growth (N&G) of disk/ellipsoidal-shaped- and spherical- particles. For the  precipitates in particular, the evolution equations for both nucleation and growth incorporated corrections for the non-spherical shape, assuming a fixed aspect ratio. In addition, special attention was paid to the choice of input material properties for simulations. These parameters included the bulk free energies of transformation, particle-matrix (misfit) elastic strain energy (for ), effective diffusivities, and the - and - interface energies. The applicability of the diffusivities and interface energies chosen for the N&G simulations was established by their consistency in replicating previously-measured rate constants for the diffusion-controlled coarsening of both  and . The N&G formulation was discretized to obtain numerical (spreadsheet) solutions via the 2 Kampmann-Wagner approach. Simulation results for the temporal evolution of volume fraction and average size of the precipitates showed good agreement with experimental measurements. The sensitivity of model predictions to various input parameters was also quantified.

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“…Lin’s study concluded that with larger grain size, the possibility of weld intersection with the grain is reduced and, therefore, the possibility of microcracking is reduced [ 16 ]. Low [ 17 ] concluded that heat treatments that dissolve intermetallic components and eutectic phases would eliminate the possibility of liquefaction at lower temperatures and improve crack resistance. Han [ 18 ] concluded that thermal cracking occurs during the solidification of molten metal under laser heating and that the crack length can be reduced by decreasing the heat input.…”

Section: Introductionmentioning

confidence: 99%

Pulsed Laser Spot Welding Thermal-Shock-Induced Microcracking of Inconel 718 Thin Sheet Alloy

Shi

Wang

et al. 2023

Materials

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This paper investigates the change in solidification microcrack susceptibility under the influence of thermal-shock-induced effects for pulsed laser spot welding molten pools with different waveforms, powers, frequencies, and pulse widths. During the welding process, the temperature of the molten pool under the effect of thermal shock changes sharply, triggering pressure waves, creating cavities in the molten pool paste area, and forming crack sources during solidification. The microstructure near the cracks was analyzed using a SEM (scanning electron microscope) and EDS (electronic differential system), and it was found that bias precipitation occurred during the rapid solidification of the melt pool, and a large amount of Nb elements were enriched in the interdendritic and grain boundaries, which eventually formed a liquid film with a low melting point, known as a Laves phase. When cavities appear in the liquid film, the chance of crack source formation is further increased. Using a slow rise and slow fall waveform is good for reducing cracks; reducing the peak laser power to 1000 w is good for reducing cracks in the solder joint; increasing the pulse width to 20 ms reduces the degree of crack damage; reducing the pulse frequency to 10 hz reduces the degree of crack damage.

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A novel approach to investigate delta phase precipitation in cold-rolled 718 alloys

Cited by 23 publications

References 38 publications

In-Situ Determination of Precipitation Kinetics During Heat Treatment of Superalloy 718

In-Situ Determination of Precipitation Kinetics During Heat Treatment of Superalloy 718

A Fast-Acting Method for Simulating Precipitation During Heat Treatment of Superalloy 718

Pulsed Laser Spot Welding Thermal-Shock-Induced Microcracking of Inconel 718 Thin Sheet Alloy

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