Effect of Delta Phase on the Hot Deformation Behaviour and Microstructural Evolution of Inconel 718

Lalvani, Himanshu; Rist, M. A.; Brooks, Jeffery

doi:10.4028/www.scientific.net/amr.89-91.313

Cited by 6 publications

(3 citation statements)

References 7 publications

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“…In the instances where flow softening occurred, the peak flow stresses likely corresponded to fracture of d phase precipitates or damage accumulation events along the d/c-c¢ interfaces. [26][27][28] The flow stress curves of the RCH alloys at 1433 K (1160°C) and 0.001/s did not show any appreciable hardening or softening which was consistent with the occurrence of superplastic forming and the absence of any observed microstructural damage. Differences in the magnitude of the peak stresses among the RCH alloys could likely be attributed to the underlying microstructure.…”

Section: B Flow Behaviorsupporting

confidence: 67%

Microstructural Stability and Hot Deformation of γ–γ′–δ Ni-Base Superalloys

Detrois

Helmink

Tin

2014

Metall Mater Trans A

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Nickel-base superalloys exhibit excellent high-temperature mechanical and physical properties and remain the first choice for structural components in advanced gas turbine engines for the aerospace propulsion and power generation applications. In response to the increasing demand for more efficient solutions and tighter requirements linked to gas turbine technologies, the properties of nickel-base superalloys can be improved by modification of their thermomechanical and/or compositional attributes. Recent investigations have revealed the potential use of ternary eutectic c-c¢-d Ni-base superalloys in advanced gas turbines due to high temperature mechanical properties that are comparable to state-of-the-art polycrystalline Ni-base superalloys. With properties largely dependent on microstructural strengthening mechanisms, both the composition and thermo-mechanical processing parameters of this novel class of alloys need to be optimized concurrently. The hot deformation characteristics of four c-c¢-d Ni-base superalloys with varying levels of Nb were evaluated at temperatures and strain rates between 1353 K and 1433 K (1080°C and 1160°C) and 0.01 to 0.001/s, respectively. Evidence of dislocation-based plasticity was observed following deformation at low temperatures and high strain rates, while high temperatures and low strain rates promoted superplasticity in these alloys. The extent of the microstructural changes and the magnitude of the cavitation damage which occurred during deformation was found to vary as a function of the alloy composition.

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Section: B Flow Behaviorsupporting

confidence: 67%

Microstructural Stability and Hot Deformation of γ–γ′–δ Ni-Base Superalloys

Detrois

Helmink

Tin

2014

Metall Mater Trans A

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“…[5,6] The proposed mechanisms for this observation ranged from boundary bulging as observed during DRX, particle stimulated nucleation (PSN) to a microstructural refinement due to grain splitting and rotation. [7,8] PSN is the recrystallization around particles because of the increased dislocation density during deformation in these zones compared to particle-free areas. PSN is commonly found during static recrystallization and includes the formation of subgrains and subsequent growth around particles larger than~1 lm.…”

Section: Introductionmentioning

confidence: 99%

Role of the Secondary Phase η During High-Temperature Compression of ATI 718Plus®

Kienl

Mandal

Lalvani

et al. 2020

Metall Mater Trans A

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High-temperature compression tests were performed on a Ni-base superalloy with a multi-phase microstructure. Particular attention was given on the influence of the g phase on recrystallization of ATI 718PlusÒ. The compression tests were performed at two temperatures over a variety of strains and strain rates. Meta-dynamic recrystallization was studied by exposing the samples to a set dwell time at the test temperature after deformation. Electron backscatter diffraction (EBSD) was used to investigate the microstructures after the tests. Secondary electron imaging (SEI) and scanning transmission electron microscopy (STEM) were utilized in order to investigate the deformation behavior of g and obtaining a detailed understanding of the recrystallization mechanism. The secondary g phase was found to increase the recrystallized fraction compared to g free tests. However, clusters of thin lamellar g inhibited recrystallization. The flow curve softening was distinctly stronger in the microstructure containing precipitates. It could be shown by SE images that this was due to the breakage and realignment of g. In addition, g was also found to accommodate the stresses by a remarkable deformation without breaking up. This was considered to be due to the composite nature of the precipitate as well as the ongoing recrystallization in the surrounding matrix.

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“…A systematic study of the flow behavior and microstructural evolution in IN718 obtained during small-scale compression experiments using three distinct microstructures has been presented in this paper. A brief synopsis of flow stress and microstructure comparison between a solution-treated and acicular d-containing microstructure has been published by authors [16]. However, the current paper provides an in-depth analysis of the role of the d phase in influencing dynamic recrystallization and flow softening in IN718.…”

Section: Introductionmentioning

confidence: 99%

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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Effect of Delta Phase on the Hot Deformation Behaviour and Microstructural Evolution of Inconel 718

Cited by 6 publications

References 7 publications

Microstructural Stability and Hot Deformation of γ–γ′–δ Ni-Base Superalloys

Microstructural Stability and Hot Deformation of γ–γ′–δ Ni-Base Superalloys

Role of the Secondary Phase η During High-Temperature Compression of ATI 718Plus®

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

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