Dislocation structure during creep of MgO single crystals

Hüther, Werner; Reppich, Bernd

doi:10.1080/14786437308217459

Cited by 76 publications

(43 citation statements)

References 10 publications

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“…The activation enthalpy is usually reported to be in the range 320-400 kJ/mol. Under those conditions, the dislocation density ρ is found to scale with the applied stress σ following the equation ρ ∼ σ m with m = 1.4 [50], or m = 2.15 [51]. At low stress (below 10 MPa) and usually above 0.6 × T m , the creep rate of MgO single crystal may exhibit a stress dependence close to 1 [52].…”

Section: High-temperature Creep Of Mgomentioning

confidence: 99%

Dislocations and Plastic Deformation in MgO Crystals: A Review

et al. 2018

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This review paper focuses on dislocations and plastic deformation in magnesium oxide crystals. MgO is an archetype ionic ceramic with refractory properties which is of interest in several fields of applications such as ceramic materials fabrication, nano-scale engineering and Earth sciences. In its bulk single crystal shape, MgO can deform up to few percent plastic strain due to dislocation plasticity processes that strongly depend on external parameters such as pressure, temperature, strain rate, or crystal size. This review describes how a combined approach of macro-mechanical tests, multi-scale modeling, nano-mechanical tests, and high pressure experiments and simulations have progressively helped to improve our understanding of MgO mechanical behavior and elementary dislocation-based processes under stress.

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Section: High-temperature Creep Of Mgomentioning

confidence: 99%

Dislocations and Plastic Deformation in MgO Crystals: A Review

et al. 2018

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“…Hüther and Reppich [45] have analysed this situation for spherical ordered precipitates and have derived a formula in which the yield stress (CRSS in original paper) decreases with increasing particle size according to:…”

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confidence: 99%

Modelling the Material Properties and Behaviour of Ni-Based Superalloys

Saunders¹,

Guo²,

Li³

et al. 2004

Superalloys 2004 (Tenth International Symposium)

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At the last two Superalloy meetings at Seven Springs, work on the development of thermodynamic modelling tools for application to multi-component Ni-based superalloys has been presented. Such modelling has become quite widespread, providing significant benefit. However, its applicability often falls short from directly providing the information that is actually required and, by itself, cannot be directly used to model properties being targeted by the end user, e.g. TTT/CCT diagrams, mechanical properties, thermophysical and physical properties. To overcome these 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, stress/strain diagrams, proof and tensile stress, hardness, coarsening of and and creep.

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“…This reveals that the process of yield is associated with the movement of dislocations to cut the tertiary precipitates which provide the principal increment of strength in a bimodal distribution of ordered precipitates [10]. The secondary precipitates are too large to cut and dislocations loop around them leaving them dislocation free.…”

Section: Discussionmentioning

confidence: 99%

Relating fundamental creep mechanisms in Waspaloy to the Wilshire equations

Deen

Whittaker

Harrison

et al. 2014

MATEC Web of Conferences

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Abstract. 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, notably those with stresses 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. In particular, the roles of recovery, tertiary gamma prime particles and dislocation foresting are examined, and related back to observations from the Wilshire fits. The virgin (untested) material has been forged and heat treated, containing some recrystallised material together with areas of more heavily deformed and recovered material clustered around the grain boundaries. Observations from tests below the 0.2% proof stress show relatively low dislocation densities away from grain boundaries and dislocation movement can be seen to be governed by interactions with the γ precipitates. In contrast, above the 0.2% proof stress, TEM observations show a substantially greater density of dislocations. The increased density provides an increment of strength through forest hardening. At stresses above the original yield point, determined by the precipitates, the creep rate is controlled by inter-action with the dislocation forest and results in an apparent activation energy change. 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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Dislocation structure during creep of MgO single crystals

Cited by 76 publications

References 10 publications

Dislocations and Plastic Deformation in MgO Crystals: A Review

Dislocations and Plastic Deformation in MgO Crystals: A Review

Modelling the Material Properties and Behaviour of Ni-Based Superalloys

Relating fundamental creep mechanisms in Waspaloy to the Wilshire equations

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