On the steady-state creep of microcellular metals

Mueller, R.; Soubielle, Sébastien; Goodall, Russell; Diologent, Frédéric; Mortensen, Alicja

doi:10.1016/j.scriptamat.2007.03.013

Cited by 23 publications

(10 citation statements)

References 21 publications

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“…This, in turn, exerts an influence on the foam stiffness, the more irregular 75 lm particles producing a more compliant foam than the 400 lm, or spherical, salt grains. [3] This lower structural efficiency of the 75 lm foam will be reflected also on the foam flow stress, [9,10] explaining why, at the same relative density, the strength of the 75 lm foams is lower than that of the 400 lm foam. This, however, does not explain why there is no response to ageing in these foams.…”

Section: Discussionmentioning

confidence: 99%

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Age‐hardening Response of Replicated Microcellular Al‐4.5%Cu

Conde

Mortensen

2008

Adv Eng Mater

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Replication processing of microcellular aluminium begins with the production of a porous preform of internally bonded NaCl powder; this is then infiltrated with aluminium or one of its alloys. [1,2] After metal solidification the NaCl preform is removed by dissolution in water to create a fine interconnected network of metal. One of the key parameters governing the mechanical properties of such a replicated foam is its microstructure, i.e. the inner microstructure of the metal it is made of. The replication process is very flexible in this regard, as it virtually allows the use of any aluminium alloy. Of particular interest in this regard are the classical age-hardening Al-Cu alloys, as these give strengths in the upper range of what is achieved in aluminium alloys.In this study we assess the response of replicated Al-4.5%Cu foams to age hardening, varying the heat-treatment parameters (time and temperature). We investigate in particular the influence of the cell size and morphology, together with that of the foam relative density, on the age hardening of these fine-scale microcellular metals. ExperimentalAl-4.5%Cu open-celled foams having cells 75 or 400 lm in diameter were produced by replication processing. [1,2] In brief, (i) cold-pressed porous NaCl powder preforms were infiltrated with molten Al-4.5%Cu, (ii) the resulting Al-4.5%Cu -NaCl composites were then machined into cylinders with 10 mm diameter and height and finally, (iii) the cylinders were immersed in water to dissolve the NaCl network. The NaCl particles used to produce the preforms are of two types, Fig. 1: (i) 400 lm particles (supplied by Fluka, St. Gallen, Switzerland) produced by NaCl precipitation and of generally equiaxed, cuboidal shape; (ii) 75 lm particles (supplied by Salines de Bex, Switzerland, trade name CP1) produced by grinding, the shape of which is less equiaxed and more irregular. This difference in particle shape is reflected in the mechanical properties of the foams, the more irregular 75 lm particles yielding, at given relative density, foams of somewhat lower Young's modulus than foams produced with equiaxed or spherical NaCl particles. [3] The cylindrical samples were solution heat-treated at 520°C for 4h under argon, and quenched before warm aging in air. Two aging temperatures (130 and 180°C), and seven aging times (2, 6, 10, 20, 54, 168 and 1000 h) were investigated. These samples were tested in compression on an MTS Alliance RT50 screw-driven testing machine, at a displacement rate of 5 lm/s (corresponding to a strain rate of 5 10 -4 ). The load was measured with a 5 kN load cell, and the strain was measured with three LVDTs fixed around the bottom compression plate and measuring the displacement of the upper plate. Table 1 gives the composition of the Al-4.5%Cu alloy used in this study, as measured by the supplier, Alusuisse, Neuhausen, Switzerland (now Rio Tinto Alcan). Figures 2a) and b) show the structure of two replicated Al-4.5%Cu foams: it is apparent that the foam mesostructure, meaning the geometrical metal di...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Age‐hardening Response of Replicated Microcellular Al‐4.5%Cu

Conde

Mortensen

2008

Adv Eng Mater

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“…More advanced properties, such as creep, have been experimentally studied for some porous metals including aluminium [114,115] , and nickel based foams [116,117] as well as the development of predictive frameworks and analytical models [118,119] , but experimental exploration for porous titanium has not been reported, reflecting the recent focus on biomedical rather than high temperature applications.…”

Section: Creepmentioning

confidence: 99%

Open Celled Porous Titanium

Shbeh

Goodall

2017

Adv Eng Mater

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[**] One of the authours (MMS) would like to acknowledge a studentship from the Iraqi Ministry of Higher Education and Scientific Research.Among the porous metals, those made of titanium attract particular attention due to the interesting properties of this element. This review examines the state of research understanding and technological development of these materials, in terms of processing capability, resultant structure and properties and the most advanced applications under development. The impact of the rise of additive manufacturing techniques on these materials is discussed, along with the likely future directions required for these materials to find practical applications on a large scale.

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“…The variational estimate of Ponte-Castañeda and Suquet [38][39][40][41][42][43], adapted and simplified for the monotonic uniaxial deformation of (incompressible) non-linear microcellular materials [6,44,45], allows an estimation of the in-situ stress-strain curves of the metal within the foams, knowing the relative density V m , the Young's modulus scaling law, and the uniaxial flow curve of the microcellular metal. The calculation is detailed in Appendix A. metal within these samples: as seen, the variational estimate collapses stress-strain curves of the five variously dense microcellular metal samples (Fig.…”

Section: Scaling Of the Flow Stressmentioning

confidence: 99%

“…At small strain and with α values in Fig. 5, the resulting error is on the order of a few percent; however, for, say, e = 10% and α = 5, then X = 2 and the flow stress is underestimated by a factor on the order of √2 (the theory being, besides, outside of its range of validity [2,6,45,51]). At high α, therefore, internal damage offers one explanation for lower-than-expected back-calculated in-situ alloy flow curves.…”

Section: Scaling Of the Flow Stressmentioning

confidence: 99%

Influence of microstructural heterogeneity on the scaling between flow stress and relative density in microcellular Al–4.5 %Cu

2014

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We explore the influence of the metal microstructure on the compressive flow stress of replicated microcellular 400 µm pore size Al-4.5wt%Cu solidified at two different solidification cooling rates, in as-cast and T6 conditions. It is found that the yield strength roughly doubles with age-hardening but does not depend on the solidification cooling rate.Internal damage accumulation, measured by monitoring the rate of stiffness loss with strain, is similar across the four microstructures explored and equals that measured in similar microcellular pure aluminium. In-situ flow curves of the metal within the open-pore microcellular material are back-calculated using the Variational Estimate of Ponte Castañeda and Suquet. Consistent results are obtained with heat-treated microcellular Al-4.5wt%Cu, and are also obtained with separate data for pure Al; however, for as-cast microcellular Al-4.5wt%Cu the back-calculated in-situ metal flow stress decreases, for both solidification rates, with decreasing relative density of the foam. We attribute this effect to an interplay between microstructural and mesostructural features of the microcellular material: variations in the latter with the former held constant can alter the scaling between flow stress and relative density within microcellular alloys.

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On the steady-state creep of microcellular metals

Cited by 23 publications

References 21 publications

Age‐hardening Response of Replicated Microcellular Al‐4.5%Cu

Age‐hardening Response of Replicated Microcellular Al‐4.5%Cu

Open Celled Porous Titanium

Influence of microstructural heterogeneity on the scaling between flow stress and relative density in microcellular Al–4.5 %Cu

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