Serrated Yielding in Alloy 718

Nalawade, Sachin; Sundararaman, M.; Singh, J.B.; Ramaswamy, Kishore; Verma, Amit Kumar

doi:10.1002/9781118495223.ch62

Cited by 5 publications

(8 citation statements)

References 22 publications

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“…These results were validated by Hayes [25], who identified analogous types of serrations in the same temperature range. Further work by Nalawade et al [26] included the effect of the strain rate in the serrated yielding behaviour of alloy 718. The uniaxial tensile tests at 6.5 × 10 −3 s −1 yielded no serrations at 200°C.…”

Section: Dynamic Strain Agingmentioning

confidence: 99%

Springback prediction and validation in hot forming of a double-curved component in alloy 718

Caro

Odenberger

Schill³

et al. 2021

Int J Mater Form

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The demands associated with the production of advanced parts made of nickel-base superalloys are continuously increasing to meet the requirements of current environmental laws. The use of lightweight components in load-carrying aero-engine structures has the potential to significantly reduce fuel consumption and greenhouse gas emissions. Furthermore, the competitiveness of the aero-engine industry can benefit from reduced production costs and shorter development times while minimizing costly try-outs and increasing the efficiency of engines. The manufacturing process of aero-engine parts in superalloys at temperatures close to 950 °C produces reduced stamping force, residual stresses, and springback compared to traditional forming procedures occurring at room temperature. In this work, a hot forming procedure of a double-curved component in alloy 718 is studied. The mechanical properties of the material are determined between 20 and 1000 °C. The presence and nature of serrations in the stress–strain curves are assessed. The novel version of the anisotropic Barlat Yld2000-2D material model, which allows the input of thermo-mechanical data, is used in LS-DYNA to model the behaviour of the material at high temperatures. The effect of considering the stress-relaxation data on the predicted shape distortions is evaluated. The results show the importance of considering the thermo-mechanical anisotropic properties and stress-relaxation behaviour of the material to predict the final geometry of the component with high accuracy. The implementation of advanced material models in the finite element (FE) analyses, along with precise process conditions, is vital to produce lightweight components in advanced materials of interest to the aerospace industry.

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Section: Dynamic Strain Agingmentioning

confidence: 99%

Springback prediction and validation in hot forming of a double-curved component in alloy 718

Caro

Odenberger

Schill³

et al. 2021

Int J Mater Form

View full text Add to dashboard Cite

show abstract

“…For instance, serrated plastic flow was reported in Waspalloy (United Technologies Corporation, Farmington, CT), [3,4] alloy 625 (Special Metals Corporation, Portland, OR), [5][6][7] Udimet 720 (Special Metals Corporation, Portland, OR), [8,9] Inconel 738 (Special Metals Corporation, Portland, OR), [10] and Inconel 718 (Special Metals Corporation, Portland, OR). [3,[11][12][13][14][15][16][17][18][19][20] Many studies have been carried out on this subject of interest contributing to a better understanding of the mechanisms and atomic species potentially involved in the occurrence of the phenomenon. The characterization of the PLC effect is based on the determination of the apparent activation energy for the occurrence of serrations on stress-strain curves and its comparison with the diffusion energy of different solute species in the alloy, which allows determination of the nature of the solute atom responsible for the interaction with mobile dislocations.…”

Section: Introductionmentioning

confidence: 99%

“…In alloy 718 (Special Metals Corporation, Portland, OR), the critical strain to the onset of the first serration, e c , evolves with temperature and strain rate following two different trends depending on the metallurgical condition of the alloy. [11,14,18,19] These domains of e c evolution are often called normal and inverse behaviors, as shown in Figure 1, adapted from a previous work. [20] As a reminder, in the normal domain (low temperature), e c decreases with an increase of temperature, whereas in the inverse domain (high temperature), e c increases with an increase of temperature.…”

Section: Introductionmentioning

confidence: 99%

“…Particularly, in alloy 718, it seems that a consensus has been reached on the subject. [3,[11][12][13][14][18][19][20] However, the origin of the high-temperature behavior is still a source of controversy, and opinions on the possible origin of serrations are divided. Whereas it is generally accepted that in the inverse domain, behavior of the PLC effect must be attributed to a substitutional atomic species, there are strong discrepancies about the nature of such solute.…”

Section: Introductionmentioning

confidence: 99%

“…Hale et al [13] considered Cr as a potential candidate on the basis of activation energy calculations, whereas Hayes and Hayes [3] suggested it was Nb, based on the disappearance of serrations for high strains resulting from the depletion of Nb in the stress field of dislocations due to the formation of NbC clusters during deformation. Nalawade et al [18,19] working on different metallurgical conditions of alloy 718, claimed that Nb is the atom responsible for the high-temperature PLC phenomenon. The reason was the earlier disappearance of serrations when increasing tensile test temperatures in samples with a matrix containing less Nb (i.e., aged and d precipitated) than in the solution-treated material.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Atomic Species Associated with the Portevin–Le Chatelier Effect in Superalloy 718 Studied by Mechanical Spectroscopy

Max

Juan

Nó

et al. 2018

Metall Mater Trans A

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In many Ni-based superalloys, dynamic strain aging (DSA) generates an inhomogeneous plastic deformation resulting in jerky flow known as the Portevin-Le Chatelier (PLC) effect. This phenomenon has a deleterious effect on the mechanical properties and, at high temperature, is related to the diffusion of substitutional solute atoms toward the core of dislocations. However, the question about the nature of the atomic species responsible for the PLC effect at high temperature still remains open. The goal of the present work is to answer this important question; to this purpose, three different 718-type and a 625 superalloy were studied through a nonconventional approach by mechanical spectroscopy. The internal friction (IF) spectra of all the studied alloys show a relaxation peak P 718 (at 885 K for 0.1 Hz) in the same temperature range, 700 K to 950 K, as the observed PLC effect. The activation parameters of this relaxation peak have been measured, E a (P 718) = 2.68 ± 0.05 eV, s 0 = 2AE10 À15 ± 1 s as well as its broadening factor b = 1.1. Experiments on different alloys and the dependence of the relaxation strength on the amount of Mo attribute this relaxation to the stress-induced reorientation of Mo-Mo dipoles due to the short distance diffusion of one Mo atom by exchange with a vacancy. Then, it is concluded that Mo is the atomic species responsible for the high-temperature PLC effect in 718 superalloy.

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Dynamic Strain Aging and Embrittlement Behavior of IN718 During High-Temperature Deformation

Saravanan

Chakravadhanula

Manwatkar

et al. 2020

Metall Mater Trans A

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Serrated Yielding in Alloy 718

Cited by 5 publications

References 22 publications

Springback prediction and validation in hot forming of a double-curved component in alloy 718

Springback prediction and validation in hot forming of a double-curved component in alloy 718

Atomic Species Associated with the Portevin–Le Chatelier Effect in Superalloy 718 Studied by Mechanical Spectroscopy

Dynamic Strain Aging and Embrittlement Behavior of IN718 During High-Temperature Deformation

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