High Temperature Deformation Behavior of Cast Alloy 718

Zhao, Deli; Guillard, S.; Male, Alan T.

doi:10.7449/1997/superalloys_1997_193_204

Cited by 11 publications

(7 citation statements)

References 6 publications

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“…temperature, strain rate, strain, etc. [2] The process parameters for billet cogging can be defined by the state variables, including strain, strain rate, and temperature. The feed rate and upset ratio in billet cogging are important to ensure the soundness of the billet.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of VIM/VAR-Processed Alloy 718 Ingot and the Evolution of Microstructure During Cogging

Park¹,

Yeom²,

Kim³

et al. 2005

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

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Alloy 718 ingot with a diameter of 300mm was made by the vacuum melting process; VIM (vacuum induction melting) followed by VAR (vacuum arc re-melting). The VIM/VAR ingot was heat-treated for homogenization, and casting structure of the ingot was broken down for uniform microstructures and mechanical properties by controlled cogging processes using a hydraulic press. The VIM/VAR-processed ingot contains three different microstructure zones along radial direction, i.e. surface chill zone, intermediate columnar gain zone, and central equiaxed zone, because the local solidification procedure varies depending on locations within the ingot. To understand the local deformation behavior and microstructure evolution, compression tests were conducted on samples collected from different zones of the ingot in wide temperature and strain rate ranges, i.e. 900~1150 o C and 0.01 s -1 . The existence of different microstructures within the ingot resulted in different compression behaviors, which was attributed to the preferred orientation in the columnar grain zone, in comparison with the equiaxed grains in the central region. At large strains, the initial difference in microstructure eventually disappeared due to dynamic, meta-dynamic, and static recrystallizations. Constitutive relations were established for the simulation of microstructure evolution, which was applied to the billet cogging process.

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Section: Introductionmentioning

confidence: 99%

Characteristics of VIM/VAR-Processed Alloy 718 Ingot and the Evolution of Microstructure During Cogging

Park¹,

Yeom²,

Kim³

et al. 2005

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

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“…However, it will be seen in the next figures that results of the stress strain calculation in this region are still very useable and provide rather good predictions for the maximum flow stress. F stresses [31,32,33,34,35] at various strains between 10% and 60% over a wide range of temperatures for 718 and 706 respectively. The results are highly satisfactory, even when stresses move the curves into the mixed deformation regime.…”

Section: Discussionmentioning

confidence: 99%

Modelling the Material Properties and Behaviour of Ni- and NiFe-Based Superalloys

Saunders¹,

Guo²,

Miodownik³

et al. 2005

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

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Over the past decade thermodynamic models have become increasingly used for Ni-and NiFebased superalloys. However, their applicability often falls short from directly providing the information that is actually required. To overcome such limitations a new computer programme has been developed, called JMatPro (an acronym for Java-based Materials Properties software). The properties which can be calculated are wide ranging, including thermo-physical and physical properties (from room temperature to the liquid state), TTT/CCT diagrams, coarsening of ' and ", and mechanical properties. It should be noted that the mechanical properties are calculated as a function of temperature and strain rate up to the melting point. Stress/strain diagrams at any given temperature and strain rate can also be generated. The creep properties that JMatPro provides include steady creep rate, rupture life and rupture strength. A feature of the new programme is that the calculations are based, as far as possible, on sound physical principles rather than purely statistical methods. Thus many of the shortcomings of methods such as regression analysis can be overcome. It allows sensitivity to microstructure to be included for many of the properties and also means that the true inter-relationship between properties can be developed, e.g. in the modelling of creep and precipitation hardening. The purpose of the present paper is to describe the technical background behind the new programme, giving extensive examples of its application and use for superalloys of the 718, 625, 706 and derivative types.

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“…Microstructural development is described using a number of purpose-built routines, which have been incorporated into the code. The dominant mechanisms for microstructural development during ingot breakdown are taken to be static recrystallisation and grain growth, which occur during periods of dwell between successive bites [ 16,171. Previous observations assume that dynamic recrystallisation has a negligible influence on the evolving structure [18,19], which has been demonstrated to occur under specific conditions of temperature and strain-rate [20].…”

Section: The Process Modelmentioning

confidence: 99%

Microstructural Evolution of Nickel-Base Superalloy Forgings during Ingot-to-Billet Conversion: Process Modeling and Validation

Dandre¹,

Walsh²,

Evans³

et al. 2000

Superalloys 2000 (Ninth International Symposium)

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A computer-based process modelling capability has been developed to simulate the evolution of microstructure during ingot-to-billet conversion of nickel-base superalloys. A unique feature of the model is the incorporation of rules describing the dynamic and static recrystallisation phenomena that govern microstructural development. Computational investigations consider the influence of process control parameters such as die velocity and displacement to obtain an optimal microstructure. Furthermore, a comparison is made of the effective strain profiles obtained by squeezing flat versus rounded sections of the workpiece.The details of the model are given with particular emphasis placed on the description of microstructural evolution. A comprehensive testing programme using a purpose built compression testing machine has been carried out to acquire the materials data required for the model. The analysis of the flow curves is described. The microstructural model has been implemented within the three-dimensional visco-plastic Forge3"t finite element software. In order to validate the methodology developed, interrupted cogging trials have been performed. The evolution of microstructure is explained in terms of the cogging model and a more optimal process procedure suggested.Nickel-base superallovs for disc annlications

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High Temperature Deformation Behavior of Cast Alloy 718

Cited by 11 publications

References 6 publications

Characteristics of VIM/VAR-Processed Alloy 718 Ingot and the Evolution of Microstructure During Cogging

Characteristics of VIM/VAR-Processed Alloy 718 Ingot and the Evolution of Microstructure During Cogging

Modelling the Material Properties and Behaviour of Ni- and NiFe-Based Superalloys

Microstructural Evolution of Nickel-Base Superalloy Forgings during Ingot-to-Billet Conversion: Process Modeling and Validation

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