Effects of local stress on the stability of tetragonal phase in ZrO2 film

Qin, Wei; Nam, Cheol; Li, H.L.; Szpunar, Jerzy A.

doi:10.1016/j.jallcom.2006.07.102

Cited by 37 publications

(14 citation statements)

References 25 publications

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“…Hence, relaxation of this stress should reduce the stabilising effect on the tetragonal phase and may partly explain the pre-transition reduction in the tetragonal phase fraction [47,48]. The expansion caused by the phase transformation is known to cause fracture in manufactured stabilised tetragonal zirconia [11], which would allow fast ingress routes into the oxide layer for oxygen containing species.…”

Section: Impact On Mechanistic Understandingmentioning

confidence: 99%

A study into stress relaxation in oxides formed on zirconium alloys

Platt

Polatidis

Frankel

et al. 2015

Journal of Nuclear Materials

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a b s t r a c tPressurised and boiling water reactors contain zirconium alloys, which are used as nuclear fuel cladding. Oxidation of these alloys, and the associated hydrogen pick-up, is a limiting factor in the lifetime of the fuel. To extend the burn-up of nuclear fuel requires control of the oxidation, and therefore development of a mechanistic understanding of the cladding corrosion process. Synchrotron X-ray diffraction (S-XRD) has been used to analyse oxide layers formed during in-situ air oxidation of Zircaloy-4 and ZIRLO™. Analysis shows that as the oxide thickness increases over time there is a relaxation of the stresses present in both the monoclinic and meta-stable tetragonal phases, and a reduction in the tetragonal phase fraction. To better understand the mechanisms behind stress relaxation in the oxide layer, finite element analysis has been used to simulate mechanical aspects of the oxidation process. This simulation was first developed based on stress relaxation in oxides formed in autoclave, and analysed ex-situ using S-XRD. Relaxation mechanisms include creep and hydrogen-induced lattice strain in the metal substrate and creep in the oxide layer. Subsequently the finite element analysis has been extended to stress relaxation observed by in-situ S-XRD oxidation experiments. Finite element analysis indicates that the impact of creep in the oxide is negligible, and the impact of both creep and hydrogen-induced lattice strain in the metal substrate metal is small. The implication is that stress relaxation must result from another source such as the development of roughness at the metal-oxide interface, or fracture in the oxide layer.

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Section: Impact On Mechanistic Understandingmentioning

confidence: 99%

A study into stress relaxation in oxides formed on zirconium alloys

Platt

Polatidis

Frankel

et al. 2015

Journal of Nuclear Materials

View full text Add to dashboard Cite

show abstract

“…The m-ZrO 2 phase has a rather well defined Raman spectrum and is always the main crystallographic phase in zirconia TGOs for temperatures relevant to corrosion in normal conditions [4,6,[9][10][11][12][13][14][31][32][33][34][35] as well as for oxidation at higher temperatures [7,8,36]. As it is the case for tetragonal or even cubic zirconia [29], 16 O substitution by the higher mass isotope 18 O induces strong downshifts of the Raman modes involving O-O or Zr-O vibrations [37].…”

Section: Introductionmentioning

confidence: 99%

The use of micro-Raman imaging to measure 18 O tracer distribution in thermally grown zirconia scales

2015

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“…This includes compressive stress, grain size, oxygen vacancies and alloying elements. Synchrotron X-ray Diffraction (S-XRD) has repeatedly shown that the oxide is strongly compressed [1][2][3][4][5][6], something which is known to stabilise the tetragonal phase in zirconium oxides [7][8][9][10][11][12]. Garvie demonstrated that $30 nm represents a critical size below which pure tetragonal zirconia can be stabilised by grain size alone [13].…”

Section: Introductionmentioning

confidence: 99%

Finite element analysis of the tetragonal to monoclinic phase transformation during oxidation of zirconium alloys

Platt

Frankel

Gass³

et al. 2014

Journal of Nuclear Materials

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a b s t r a c tCorrosion is a key limiting factor in the degradation of zirconium alloys in light water reactors. Developing a mechanistic understanding of the corrosion process offers a route towards improving safety and efficiency as demand increases for higher burn-up of fuel. Oxides formed on zirconium alloys are composed of both monoclinic and meta-stable tetragonal phases, and are subject to a number of potential mechanical degradation mechanisms. The work presented investigates the link between the tetragonal to monoclinic oxide phase transformation and degradation of the protective character of the oxide layer. To achieve this, Abaqus finite element analysis of the oxide phase transformation has been carried out. Study of the change in transformation strain energy shows how relaxation of oxidation induced stress and fast fracture at the metal-oxide interface could destabilise the tetragonal phase. Central to this is the identification of the transformation variant most likely to form, and understanding why twinning of the transformed grain is likely to occur. Development of transformation strain tensors and analysis of the strain components allows some separation of dilatation and shear effects. Maximum principal stress is used as an indication of fracture in the surrounding oxide layer. Study of the stress distributions shows the way oxide fracture is likely to occur and the differing effects of dilatation and shape change. Comparison with literature provides qualitative validation of the finite element simulations.

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Effects of local stress on the stability of tetragonal phase in ZrO2 film

Cited by 37 publications

References 25 publications

A study into stress relaxation in oxides formed on zirconium alloys

A study into stress relaxation in oxides formed on zirconium alloys

The use of micro-Raman imaging to measure 18 O tracer distribution in thermally grown zirconia scales

Finite element analysis of the tetragonal to monoclinic phase transformation during oxidation of zirconium alloys

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