Applicability of Solid Solution Heat Treatments to  Aluminum Foams

Lázaro, Jaime; Solórzano, E.; Escudero, José Antonio; Saja, J.A. de; Rodríguez‐Pérez, Miguel Ángel

doi:10.3390/met2040508

Cited by 11 publications

(6 citation statements)

References 36 publications

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“…Regarding the cellular structure of the foams, Figure a shows the internal aspect (microtomography slice at the mid‐height) of a foam with a porosity of 0.76 (thus relative density, ρ r = 0.24) and a pore connectivity grade of 80%. The foam present a cylindrical symmetry and the material is distributed with a certain gradient in the radial direction from the center to the lateral skin as already reported elsewhere . Small pores appear near the outer region, while the bigger pores (lower density) tend to be located in the central region.…”

Section: Understanding and Controlling The Generation Of Defects Durisupporting

confidence: 59%

Clues for Cellular Structure Optimization in Aluminum Foams

2016

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This work studies the different stages of the fabrication of aluminum foams from PM precursors and aims on finding the parameters affecting the generation of defects in the cellular structure. Results show that foam's cellular anisotropy is directly related to the structural anisotropy of the initial precursor and the way it starts expanding. Homogenization heat treatment to the precursor material can then reduce foam's cellular anisotropy. On the other hand, the amount of broken cell walls depends not only on the expansion grade, but more significantly on the cooling conditions at the end of the foaming process, being this a possible key to reduce and control their generation.

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Section: Understanding and Controlling The Generation Of Defects Durisupporting

confidence: 59%

Clues for Cellular Structure Optimization in Aluminum Foams

2016

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“…There are basically two ways of improving a metal foams mechanical performance: Either the properties of the matrix can be adjusted, or potential deficiencies in the pore structure can be eliminated. The former has been done in the past via heat treatments, given that suitable matrix alloys susceptible to precipitation hardening were employed . The second approach is harder to realize specifically if structure evolution is a stochastic process.…”

Section: Introductionmentioning

confidence: 99%

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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“…The relevance of such investigations is stressed by the fact that due to their good processing characteristics, near-eutectic Al-Si alloys in a composition range from approximately 7 wt.% Si upwards and related systems, e.g., containing further additions of Mg or Cu, have retained their role as backbone both in classic metal foam and metal foam sandwich production [2,27] and in more recent developments such as Advanced Pore Morphology (APM) foams [28][29][30][31]. In its concentration on additive-based microstructure modification, the approach complements studies on heat treatment of foams [32][33][34] and variation of the matrix alloy [35][36][37]. Of these, when it comes to identifying the role of matrix alloy and specifically microstructure, the latter will suffer greatly from coincidental differences in expansion characteristics and thus pore structure, as has recently been shown in much detail by Helwig et al [38].…”

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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Applicability of Solid Solution Heat Treatments to Aluminum Foams

Cited by 11 publications

References 36 publications

Clues for Cellular Structure Optimization in Aluminum Foams

Clues for Cellular Structure Optimization in Aluminum Foams

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

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