Hierarchical Structure of Aluminium Foams and Relation to Compression Behaviour

Mosler, Ulrike; Lehmhus, Dirk; Müller, Alexandra; Heinzel, G.

doi:10.1515/htmp.2007.26.4.291

Cited by 4 publications

(3 citation statements)

References 3 publications

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“…From the same perspective, they confirm many theoretical studies and assumptions . However, the level of the observed effects is surprisingly high when considering that many previous investigations conclude that structural deviations have significantly less impact on mechanical performance than for example global density : Martin et al, based on their set of AlSiMg 0.5 and AlSi7 samples prepared using as‐received TiH 2 , assume structure‐based strength variation to reach an order of magnitude of 20% , whereas in the present study, a strength increase of roughly 50% was determined for both maximum and plateau onset strength in structurally optimized compared to reference materials at 0.5 g/cm 3 , which matches the lowest densities considered by Martin et al. (approx.…”

Section: Resultssupporting

confidence: 87%

Mechanical performance of structurally optimized AlSi7 aluminum foams – an experimental study

Lehmhus

Busse

2014

Materialwissenschaft Werkst

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AlSi7 aluminum foams produced via the powder compact melting process suffer from deficiencies in the pore structure that are linked to the mismatch between the decomposition temperature range of the common blowing agent TiH2 and the solidus and liquidus temperature of the matrix alloy. To alleviate these deficiencies, two main paths have been discussed in the past: One is the adaptation of the matrix alloy towards lower melting temperatures, the other the modification by heat treatment of the foaming agent itself, which leads to higher decomposition temperatures. The present paper compares the mechanical response of foams produced according to the second approach to that of the reference material, AlSi7 foamed using untreated TiH2 as blowing agent. Mechanical performance is evaluated based on uniaxial, quasi‐static compression tests over a wide range of densities. In parallel, the pore and microstructure of the respective materials is characterized using metallographic sections and computed tomography for image acquisition, as well as image analysis to derive quantitative parameters. Foams based on thermally treated blowing agents show increased compressive strength at technically relevant density levels. The advantage is lost at very high porosities in excess of 85–90% only.

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Section: Resultssupporting

confidence: 87%

Mechanical performance of structurally optimized AlSi7 aluminum foams – an experimental study

Lehmhus

Busse

2014

Materialwissenschaft Werkst

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“…One major step to this end is an improved understanding of the role of different structural features in determining the mechanical properties, as well as their scatter. Both, however, are influenced by several characteristics, among which Mosler et al and Martin et al suggest the following hierarchy [8,9]: (a) global density (b) foam structure (c) matrix alloy (d) foam microstructure Mu et al introduce friction between cell walls as a further mechanism influencing behavior under compressive load, which, however, becomes effective only at high strain levels beyond the stress-strain curve's typical plateau [10]. Density as the dominating aspect may be subdivided into global density and systematic density variations such as density gradients as typically induced by foam drainage, or by solidification shrinkage.…”

Section: Foam Fundamentalsmentioning

confidence: 99%

Effects of Eutectic Modification and Grain Refinement on Microstructure and Properties of PM AlSi7 Metallic Foams

Lehmhus

Hünert

Mosler

et al. 2019

Metals

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For AlSi7 foams, microstructure modification by variation of solidification rates and addition of Sr, B and TiB2/TiAl3 was investigated and its transfer to powder metallurgical metal foaming processes demonstrated. Microstructural characterization focused on grain size and morphology of the eutectic phase. Cooling rates during solidification were linked to secondary dendrite arm spacing, establishing a microstructure-based measure of solidification rates. Effects of refining and modification treatments were compared and their influence on foam expansion evaluated. Studies on foams focused on comparison of micro- and pore structure using metallographic techniques as well as computed tomography in combination with image analysis. Reference samples without additives and untreated as well as annealed TiH2 as foaming agent allowed evaluation of pore and microstructure impact on mechanical performance. Evaluation of expansion and pore structure revealed detrimental effects of Sr and B additions, limiting the evaluation of mechanical performance to the TiB2 samples. These, as well as the two reference series samples, were subjected to quasi-static compression testing. Stress-strain curves were gained and density-dependent expressions of ultimate compressive strength, plateau strength and tangent modulus derived. Weibull evaluation of density-normalized mechanical properties revealed a significant influence of grain size on the Weibull modulus at densities below 0.4 g/cm3.

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“…3,9,10] based on an idealized representation of cellular structure were found to be inadequate to represent the actual profile of mechanical properties for real porous metals and metallic foams [9,10]. Different imperfections existing in real Al foams, processing additives, and variation in the testing conditions result in considerable disagreements between experimental results and theoretical predictions [10,[15][16][17][18][19][20][21][22]. Thus, specification of mechanical tests for porous Al and Al foams with well-defined data related to microstructure of the cell wall material is a way to provide for validity of material verification essential for engineering design.…”

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confidence: 99%

Mechanical Behaviour of the Porous and Foam Aluminium in Conditions of Compression: Determination of Key Mechanical Characteristics

Byakova¹,

Vlasov²,

Semenov³

et al. 2017

Metallofiz. Noveishie Tekhnol.

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The paper emphasizes harmonized recommendations for mechanical tests of highly-porous aluminium and aluminium foam to be applicable for analysing their compression response under quasi-static loading as well as determining reliable and reproducible results essentially required for practice problems of engineering design. Key mechanical parameters are designated and specified by considering distinctive features of deformation patterns indicative of porous aluminium and aluminium foam with a cellular structure. Special attention is paid to the problem related to inhomogeneous deformation of the above-mentioned materials, resulting in variation of quasi-elastic structural stiffness as well as shape and length of plateau regime of the stress-strain curve. Application of the harmonized recommendations is demonstrated with using several kinds of foam aluminium fabricated in line with different processing route. Using the above recommendation, significant effect of processing additives on micromechanism of deformation and, in turn, on macroCorresponding author: Oleksandra Viktorivna Zatsarna E-mail: alexsandra.ku@gmail.com Key words: porous metals, metallic foams, compression test, quasi-static loading.В роботі висвітлено новітні унормовані рекомендації стосовно механічних випробувань високопоруватого та спіненого алюмінію, які є придатними для аналізу механічної поведінки цих матеріялів в умовах стиснення та отримання надійних та відтворюваних результатів, істотно необхідних для вирішення задач інженерної практики. З урахуванням особливостей деформаційних кривих, притаманних комірчастій структурі високопору-ватого та спіненого алюмінію, надано відомості щодо визначення їхніх ключових механічних характеристик. Особливу увагу приділено неодно-рідному характеру деформації зазначених матеріялів, що спричиняє змі-ни у структурній цупкості, а також формі та довжині ділянки плато на кривій «напруження-деформація». Застосування унормованих рекомен-дацій було продемонстровано із застосуванням декількох видів спіненого алюмінію, виготовленого за різними технологічними процедурами. З урахуванням висвітлених рекомендацій зареєстровано істотний вплив технологічних додатків на мікромеханізм деформації та, як наслідок, на механічну поведінку спіненого алюмінію в цілому, що пояснюється за-брудненням матеріялу стінок між комірками сторонніми продуктами ре-акцій.Ключові слова: пористі метали, металеві піни, випробування на стиск, квазистатичне навантаження.В работе приведены современные рекомендации для механических испы-таний высокопористого и вспененного алюминия, которые пригодны для анализа механического поведения этих материалов в условиях сжатия и получения надёжных и воспроизводимых результатов, необходимых для решения задач инженерной практики. С учётом особенностей деформаци-онных кривых, присущих ячеистой структуре высокопористого и вспе-ненного алюминия, представлены сведения относительно определения их ключевых механических характеристик. Особое внимание уделено неод-нородному характеру деформации указанных материалов, что ...

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Hierarchical Structure of Aluminium Foams and Relation to Compression Behaviour

Cited by 4 publications

References 3 publications

Mechanical performance of structurally optimized AlSi7 aluminum foams – an experimental study

Mechanical performance of structurally optimized AlSi7 aluminum foams – an experimental study

Effects of Eutectic Modification and Grain Refinement on Microstructure and Properties of PM AlSi7 Metallic Foams

Mechanical Behaviour of the Porous and Foam Aluminium in Conditions of Compression: Determination of Key Mechanical Characteristics

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