Recent Advances in Creep Modelling of the Nickel Base Superalloy, Alloy 720Li

Harrison, W. J.; Whittaker, Mark; Williams, S.

doi:10.3390/ma6031118

Cited by 31 publications

(26 citation statements)

References 21 publications

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“…A wide range of materials [24,25,26,27] have now been studied for which optimised fits are obtained when the value of the apparent activation energy (Q c *) is allowed to vary either side of the break point. Interestingly, the most significant changes in the apparent activation energy observed have been in stainless steel grade 316, with values of 250 kJ/mol observed above the yield stress, decreasing to 150 kJ/mol below.…”

Section: Introductionmentioning

confidence: 99%

Creep Deformation by Dislocation Movement in Waspaloy

et al. 2017

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Creep tests of the polycrystalline nickel alloy Waspaloy have been conducted at Swansea University, for varying stress conditions at 700 °C. Investigation through use of Transmission Electron Microscopy at Cambridge University has examined the dislocation networks formed under these conditions, with particular attention paid to comparing tests performed above and below the yield stress. This paper highlights how the dislocation structures vary throughout creep and proposes a dislocation mechanism theory for creep in Waspaloy. Activation energies are calculated through approaches developed in the use of the recently formulated Wilshire Equations, and are found to differ above and below the yield stress. Low activation energies are found to be related to dislocation interaction with γ′ precipitates below the yield stress. However, significantly increased dislocation densities at stresses above yield cause an increase in the activation energy values as forest hardening becomes the primary mechanism controlling dislocation movement. It is proposed that the activation energy change is related to the stress increment provided by work hardening, as can be observed from Ti, Ni and steel results.

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Section: Introductionmentioning

confidence: 99%

Creep Deformation by Dislocation Movement in Waspaloy

et al. 2017

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“…The microstructure consists of a grain size of approximately 6-32 µm with primary γ ' (Ni 3 (Al,Ti)) measuring 3-5 µm distributed on the grain boundaries, and secondary γ ' measuring 70-120 nm, shown in Fig. 1 [2]. The chemical composition of 720Li is reported in Table 1.…”

Section: Methodsmentioning

confidence: 99%

Factors affecting the corrosion fatigue life in nickel based superalloys for disc applications

Rosier

Perkins

Girling

et al. 2014

MATEC Web of Conferences

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Abstract. The nickel based superalloy 720Li is employed in the gas turbine due to its mechanical performance at elevated temperature. A comprehensive assessment of the materials behaviour under representative service conditions is reported to address the drive for ever increasing temperatures and more arduous environmental exposure. Fatigue experiments have been performed in an air and air/SO x environment at 700• C containing a mixed salt as a contaminant. There is an intimate relationship between local salt level (flux), stress level and stress state, i.e. static or cyclic. The interaction with these variables with the work hardened layer present on the surface of all tested specimens as a result of the shot peening process directly affects the crack initiation process. If specific conditions of environment and stress are achieved, a significant reduction in fatigue life is observed.

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“…The Ni-based polycrystalline wrought superalloys have been developed to provide superior mechanical properties and good corrosion resistance at high temperatures, leading to a wide application on manufacturing turbine disks, blades and vanes in gas turbines and aero-engines. The high temperature strength is usually provided by a distribution of γ' (Ni 3 (Al, Ti)) precipitates which hinder dislocation movement [1]. To obtain the properties of these materials under the conditions of service, experimental investigations has been previously carried out and complex deformation behaviors have been exhibited [2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Unified modeling of high temperature deformations of a Ni-based polycrystalline wrought superalloy under tension-compression, cyclic, creep and creep-fatigue loadings

Huang

Shi

Yang

et al. 2014

Sci. China Technol. Sci.

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The complex deformation behaviors under tension-compression, cyclic, creep and creep-fatigue loadings of a nickel-base polycrystalline wrought superalloy at 650°C and 700°C were experimentally investigated. To uniformly simulate the complex deformation behaviors, the modified viscoplastic constitutive model combined with both the Kachanov damage evolution equation and the Ohno-Wang modification was formulated on the basis of the Chaboche theory. The simulated results on tension-compression behavior, cyclic viscoplastic and creep deformations showed comprehensive predicting ability. With the obtained material parameters, the deformations in creep-fatigue interaction under three dwell types were simulated and the capability of the modified model was further verified with good accuracy. superalloy, constitutive relation, fatigue, creep, creep-fatigue interaction Citation:Huang J, Shi D Q, Yang X G, et al. Unified modeling of high temperature deformations of a ni-based polycrystalline wrought superalloy under tension-compression, cyclic, creep and creep-fatigue loadings.

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Recent Advances in Creep Modelling of the Nickel Base Superalloy, Alloy 720Li

Cited by 31 publications

References 21 publications

Creep Deformation by Dislocation Movement in Waspaloy

Creep Deformation by Dislocation Movement in Waspaloy

Factors affecting the corrosion fatigue life in nickel based superalloys for disc applications

Unified modeling of high temperature deformations of a Ni-based polycrystalline wrought superalloy under tension-compression, cyclic, creep and creep-fatigue loadings

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