Creep cavitation in metals

Kassner, M.E.; Hayes, Troy A.

doi:10.1016/s0749-6419(02)00111-0

Cited by 339 publications

(185 citation statements)

References 115 publications

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“…The refined grain structure can promote the accumulation of creep damage due to locally increased grain boundary diffusion, [31] combined with a reduced ability of the second-phase particles to inhibit grain boundary motion.…”

Section: Discussionmentioning

confidence: 99%

The Influence of Thermal Cycles on the Microstructure of Grade 92 Steel

West

Siefert³

et al. 2017

Metall Mater Trans A

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The microstructure in the heat-affected zone (HAZ) of welds made from the 9 wt pct chromium martensitic Grade 92 steel is complex and has not yet been completely understood. There is a lack of systematic microstructural investigations to define the different regions of the microstructure across the HAZ of Grade 92 steel welds as a function of the welding process. In this study, the microstructure in the HAZ of an as-fabricated single-pass bead-on-plate weld on a parent metal of Grade 92 steel was systematically investigated by using an extensive range of electron and ion-microscopy-based techniques. A dilatometer was used to apply controlled thermal cycles to simulate the microstructures in the different regions of the HAZ. A wide range of microstructural properties in the simulated materials were then characterized and compared with the experimental observations from the weld HAZ. It was found that the microstructure in the HAZ of a single-pass Grade 92 steel weld can be categorized as a function of a decreasing peak temperature reached as (1) the completely transformed (CT) region, in which the original matrix is completely reaustenitized with complete dissolution of the pre-existing secondary precipitate particles; (2) the partially transformed (PT) region, where the original matrix is partially reaustenitized along with a partial dissolution of the secondary precipitate particles from the original matrix; and (3) the overtempered (OT) region, where the pre-existing precipitate particles coarsen. The PT region is considered to be the susceptible area for damage in the commonly reported HAZ failures in weldments constructed from these types of steels.

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Section: Discussionmentioning

confidence: 99%

The Influence of Thermal Cycles on the Microstructure of Grade 92 Steel

West

Siefert³

et al. 2017

Metall Mater Trans A

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“…The theoretical approaches involve nucleation of cavities and voids or wedges and subsequent growth, either of them possibly rate controlling [Kassner and Hayes, 2003;Riedel, 1986Riedel, , 1993Tvergaard, 1990;2009]. Mechanisms of cavity nucleation are still poorly understood.…”

Section: Cavitation and Ductile Failurementioning

confidence: 99%

Superplasticity and ductile fracture of synthetic feldspar deformed to large strain

Rybacki¹,

Wirth²,

Dresen³

2010

J. Geophys. Res.

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[1] We performed high-strain torsion experiments on fine-grained (≈4 mm) anorthite aggregates in a Paterson-type gas deformation apparatus. The dense hydrous (≈0.1 wt% H 2 O) samples contain < 3 vol% Si-enriched residual glass located at triple junctions. Specimens were twisted at constant rate to a maximum shear strain of about 5 at experimental conditions of 100-400 MPa confining pressure, temperatures of 950°C-1200°C, and shear strain rates of ≈2 × 10 −5 , 5 × 10 −5 , and 2 × 10 −4 s −1 . Resulting maximum shear stresses at the sample periphery were in the range of ≈2-80 MPa. The samples showed strain hardening at slow deformation rate and strain weakening at fast strain rate, respectively. Fitting the stress strain rate data to a power law yields linear viscous behavior. Microstructural analysis shows locally enhanced dislocation density, suggesting diffusion-assisted and/or dislocation-assisted grain boundary sliding as the dominant deformation mechanism. Deformed samples exhibit abundant cavities, nucleated mostly at grain triple junctions and at grain boundaries in response to cooperative grain boundary sliding. At shear strains ≥ 2, growth and coalescence of the cavities form an anastomozing network of regularly spaced strings oriented at about 30°to the direction of maximum compressive stress and ∼15°to the shear plane. Strain is localized along these shear bands associated with a shape-preferred orientation of high-aspect ratio feldspar grains and with segregation of initial pore fluids (residual glass) into the bands. More than one third of the samples were deformed to terminal failure that occurred suddenly at shear strains of ≈3-5. The experiments indicate that cavitation damage may facilitate fluid flow and deep seismicity in highly strained shear zones.Citation: Rybacki, E., R. Wirth, and G. Dresen (2010), Superplasticity and ductile fracture of synthetic feldspar deformed to large strain,

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“…Cavitation, formation of submicroscopic cavities driven primarily by diffusion and accumulation of vacancies, is the direct consequence of GBS. When GBS cannot be fully compensated by diffusion and/or dislocation creep controlled grain shape change, cavities nucleate at first on grain boundaries at high angle to the tensional direction (direction of s 3 ) [Č adek, 1988;Kassner and Hayes, 2003]. Cavities then grow and coalesce with each other to form intergranular voids.…”

Section: Cavitation Versus Fracturing Driven By Melt Overpressurementioning

confidence: 99%

Extreme ductility of feldspar aggregates—Melt‐enhanced grain boundary sliding and creep failure: Rheological implications for felsic lower crust

Závada

Schulmann²,

Konopásek

et al. 2007

J. Geophys. Res.

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[1] High-grade orthogneisses from granulite-bearing lower crustal unit show extreme finite strains of both K-feldspar and plagioclase with respect to weakly deformed quartz aggregates. K-feldspar aggregate in the most intensely deformed sample shows interstitial grains of quartz and albite, which also mark some intragranular fractures within K-feldspar grains. Both interstitial grains and fractures are oriented mostly perpendicular to the sample stretching lineation. Quartz and albite grains within K-feldspar bands are interpreted as crystallized from interstitial melt and the petrology study shows that the melt was produced by a metamorphic reaction in plagioclase-mica bands. Thermodynamic Perple_X modeling shows that melt volume increase was negligible and melt amount was too small to generate considerable melt overpressure for calculated PT conditions. It is therefore suggested that dilation of K-feldspar aggregates and fracturing of its grains represent a final creep failure state, which resulted from the cavitation process accompanying grain boundary sliding controlled diffusion creep. The consequence of cavitation-driven dilation of K-feldspar aggregates is the local underpressure resulting in infiltration of melt from plagioclase bands. Analogy with metallurgy experiments shows that the cavitation process, exclusively developed in cryptoperthitic K-feldspar, can be attributed to its lower purity compared to more pure plagioclase. Contrasting rheological behavior of feldspars with respect to quartz prior to fracturing is attributed to different deformation mechanisms. Feldspars appear weaker due to grain boundary sliding accommodated by coupled melt-enhanced diffusion creep along grain boundaries and dislocation creep within grains, in contrast to quartz deforming via grain boundary migration accommodated dislocation creep.Citation: Závada, P., K. Schulmann, J. Konopásek, S. Ulrich, and O. Lexa (2007), Extreme ductility of feldspar aggregates-Meltenhanced grain boundary sliding and creep failure: Rheological implications for felsic lower crust,

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Creep cavitation in metals

Cited by 339 publications

References 115 publications

The Influence of Thermal Cycles on the Microstructure of Grade 92 Steel

The Influence of Thermal Cycles on the Microstructure of Grade 92 Steel

Superplasticity and ductile fracture of synthetic feldspar deformed to large strain

Extreme ductility of feldspar aggregates—Melt‐enhanced grain boundary sliding and creep failure: Rheological implications for felsic lower crust

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