Hot forging of IN718 with solution-treated and delta-containing initial microstructures

H. M. Lalvani, J. W. Brooks

Research output: Contribution to journalArticle

Abstract

A systematic study of the effect of δ 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 δ precipitates, and (III) a microstructure containing dense network of intragranular and grain boundary δ 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 δ 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 δ phase, and to a certain degree of mechanical grain refinement caused by distortion and offsetting of grain segments where a dense δ-platelet structure exists.
LanguageEnglish
Pages1-10
Number of pages10
JournalMetallography, Microstructure, and Analysis
Early online date29 Jul 2016
DOIs
Publication statusE-pub ahead of print - 29 Jul 2016

Fingerprint

Forging
Precipitates
Microstructure
Platelets
Dynamic recrystallization
Hot working
Grain refinement
Microstructural evolution
Nickel
Plastic flow
Superalloys
Temperature
Strain rate
Dissolution
Grain boundaries
Compaction

Keywords

  • bulk deformation
  • delta phase
  • nickel-based superalloys
  • thermomechanical processing
  • recrystallization

Cite this

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title = "Hot forging of IN718 with solution-treated and delta-containing initial microstructures",
abstract = "A systematic study of the effect of δ 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 δ precipitates, and (III) a microstructure containing dense network of intragranular and grain boundary δ 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 δ 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 δ phase, and to a certain degree of mechanical grain refinement caused by distortion and offsetting of grain segments where a dense δ-platelet structure exists.",
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Hot forging of IN718 with solution-treated and delta-containing initial microstructures. / Lalvani, H. M.; Brooks, J. W.

In: Metallography, Microstructure, and Analysis, 29.07.2016, p. 1-10.

Research output: Contribution to journalArticle

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N2 - A systematic study of the effect of δ 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 δ precipitates, and (III) a microstructure containing dense network of intragranular and grain boundary δ 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 δ 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 δ phase, and to a certain degree of mechanical grain refinement caused by distortion and offsetting of grain segments where a dense δ-platelet structure exists.

AB - A systematic study of the effect of δ 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 δ precipitates, and (III) a microstructure containing dense network of intragranular and grain boundary δ 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 δ 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 δ phase, and to a certain degree of mechanical grain refinement caused by distortion and offsetting of grain segments where a dense δ-platelet structure exists.

KW - bulk deformation

KW - delta phase

KW - nickel-based superalloys

KW - thermomechanical processing

KW - recrystallization

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