Creep and Stress Rupture Behavior of Aluminum As a Function of Purity

Servi, Italo S.; Grant, N.J.

doi:10.1007/bf03397400

Cited by 41 publications

(50 citation statements)

References 7 publications

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“…The incorrect choice of the same value of a for materials of different purities is more likely to justify the dissimilarity. [40] and creep data from the literature (superpurity aluminum, 99.9945 pct Al), [41] showing the compatibility of hot-working data obtained at high strain rates and strains from both conventional material and nanostructured powders with those of creep obtained at low strain rates and strains. Data plotted according to Eq.…”

Section: Resultsmentioning

confidence: 88%

“…As will be seen later, the deformation mechanisms operating during the hot working of conventional materials are indeed similar, but before elaborating on this theme, a comparison will be made of the stress-strain-rate relationship for the creep and hot extrusion of conventional materials and nanostructured powders. Figure 1(b) shows data from the literature on the strain rate vs sinh (ar) in the case of hot extrusion [40] and aluminum creep [41] plotted with the experimental extrusion data obtained in the present work. The similarity of the stress dependence of the extrusion strain rate to that of extrusion and creep of conventional material is somewhat surprising, mainly with respect to creep, because the extrusion strain rates are several orders of magnitude higher than those found in creep.…”

Section: Resultsmentioning

confidence: 92%

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Effect of Dislocation Mechanisms during Extrusion of Nanostructured Aluminum Powder Alloy

Jorge

Peres

Kiminami

et al. 2009

Metall Mater Trans A

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Nanostructured Al-3.0Fe-0.42Cu-0.37Mn powder alloy was deformed by extrusion over a temperature range of 375°C to 425°C, a ram speed range of 1 to 30 mm/s, and an extrusion rate of 10:1. Flow stresses and strain rates were calculated from the experimental ram pressures and speeds. The stress-strain-rate-temperature relationship in the extrusion of the nanostructured alloy was found to be similar to that in hot-worked conventional materials. The extrusion, torsion, compression, and creep data of nanostructured and conventional materials, extending over ten orders of magnitude of strain rate and over two orders of magnitude of stress, were correlated by a hyperbolic-sine constitutive equation, because the power and exponential laws lose linearity at high and low stresses, respectively. The hyperbolic-sine equation is widely used to correlate the hot-working behavior of conventional materials. It was concluded that the hot working of nanostructured powders is a thermally activated process in which the rate-controlling mechanism is the climb of edge dislocations. Microstructural changes in the consolidated alloys as a function of the extrusion conditions were investigated. An analysis was made of the dislocation behavior in very small grains of nanostructured metal by transmission electron microscopy (TEM) and we identified a dislocation structure and the different ways it appears in 40-to 100-nm Al-alloy grains. We also discuss the thermally activated propagation of dislocations and their interactions with shear bands/grain boundaries (SBs/GBs), and dislocation loops. Microstructural features including low-angle GBs, high-angle GBs, and equilibrium GBs and subgrain boundaries were observed. Dislocation structures under a deformation condition were studied to investigate the microstructural evolutions, which revealed some unique microstructural features such as dislocation tangle zones (DTZs) and dense-dislocation walls (DDWs), and the recovery process is discussed herein.

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Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 92%

Effect of Dislocation Mechanisms during Extrusion of Nanostructured Aluminum Powder Alloy

Jorge

Peres

Kiminami

et al. 2009

Metall Mater Trans A

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“…Indeed, second phase particles were often found to be necessary in most cases to reduce grain boundary migration and to cause cavitation (47,48).…”

Section: Intergranular Cavitation In Creepmentioning

confidence: 99%

Creep cavitation in 304 stainless steel

Chen¹,

Argon²

1981

Acta Metallurgica

182

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A micromechanical analysis of deformation and fracture in creeping alloys is presented based on a mechanistic approach using continuum mechanics. The analysis was first carried out on a coarse microscopic level in which the self-consistent theory of Hill was employed to treat the steady state creep of heterogeneous alloys with coarse microstructures allowing for grain boundary sliding. Processes operating on a finer scale than the grain size such as grain boundary diffusion and surface diffusion were subsequently included in the analysis. It was found that the high stresses required for cavity nucleation occur at intergranular particles only in transients of grain boundary sliding, and that two modes of cavity growth result corresponding to rate control by each of the abovementioned diffusional processes.Creep cavitation in 304 stainless steel in the neighborhood of 0.5 Tm was studied experimentally to test these theoretical models. Our results suggest that a broad spectrum of interfacial energy may exist and that microstructural changes such as those caused by twins can alter cavitation behavior drastically. Cavities grow in most cases by grain boundary diffusion coupled with matrix creep, somewhat restricted by surface diffusion. However, the grain boundary sliding can be a dominant mode of cavity growth at high stresses and for large cavities.

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“…Although a Peierls stress is not usually considered to be of importance for fcc alloys, recent studies suggest that this conclusion is not true for Al. With ab initio methods, Shin and Carter (24) is compared to experimental data from [27].…”

Section: Pure Elementsmentioning

confidence: 99%

Fundamental Models for the Creep of Metals

Sandström¹

2018

Creep

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Creep and Stress Rupture Behavior of Aluminum As a Function of Purity

Cited by 41 publications

References 7 publications

Effect of Dislocation Mechanisms during Extrusion of Nanostructured Aluminum Powder Alloy

Effect of Dislocation Mechanisms during Extrusion of Nanostructured Aluminum Powder Alloy

Creep cavitation in 304 stainless steel

Fundamental Models for the Creep of Metals

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