Influence of heat treatments on the microstructure and mechanical behaviour of open cell AlSi7Mg0.3 foams on different lengthscales

Schüler, Paul; Frank, Robert; Uebel, David; Fischer, Sebastian; Bührig–Polaczek, Andreas; Fleck, Claudia

doi:10.1016/j.actamat.2016.02.041

Cited by 40 publications

(26 citation statements)

References 26 publications

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“…Figure displays the volumetric energy absorption up to densification strain of open‐cell steel foams manufactured in this study and literature data for aluminum alloy foams with different relative densities . As can be seen, energy absorption in metal foams is a strong function of yield strength and intrinsic strain hardening of the base material and the relative density of the foam.…”

Section: Resultsmentioning

confidence: 99%

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Investment Casting and Mechanical Properties of Open‐Cell Steel Foams

Frömert¹,

Lott²,

Matz³

et al. 2019

Adv Eng Mater

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This study presents a novel manufacturing process for open-cell stainless steel foams using a modified investment casting process and a novel approach to identify transitions between elastic-plastic, plateau, and densification region in the stress-strain history of compressed foams, based on its strain and structural hardening behavior. The influence of microstructure on the mechanical properties under quasi-static compression loading (plateau stress, energy absorption, and strain hardening) of austenitic (AISI 304, 316L) and super duplex (AISI F55) stainless steels is investigated. Microstructure is characterized prior and subsequent to mechanical testing using light microscopy and SEM. The manufacturing process yields open-cell foams with relative densities in the range of 14-20%, solid struts being circular in shape and defect-free surfaces. This morphology leads to improved yield strengths compared to open-cell steel foams produced by the powder metallurgical route. Among the manufactured open-cell steel foams, F55 foams with finegrained duplex microstructures show highest yield strength, strain hardening, and energy absorption with a sufficient ductility. Although a martensitic transformation is present in highly deformed struts of soft austenitic stainless steel foams, strain hardening in the plateau region is lower compared to duplex foams.

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Section: Resultsmentioning

confidence: 99%

“…Energy absorption of open‐cell steel foams up to densification strain ϵ d compared to literature data for aluminum alloy foams …”

Section: Resultsmentioning

confidence: 99%

Investment Casting and Mechanical Properties of Open‐Cell Steel Foams

Frömert¹,

Lott²,

Matz³

et al. 2019

Adv Eng Mater

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“…The mechanical properties of open‐cell foam struts generally differ from those of bulk metal specimens, due to a variety of reasons including differences in the testing methods, microstructures and geometry. The difficulties in testing the tiny struts have been addressed in several studies . Due to these challenges the results of the micro‐tensile tests scatter to a large extent.…”

Section: Discussionmentioning

confidence: 99%

“…Microtensile testing set‐ups for Al‐alloy (AlSi7Mg0.3) foam struts have been improved by fixing the struts by polyurethane resin in sockets or by glueing them on metal plates; the sockets or the plates were then mounted in the testing devices. Both studies gave values for Young's modulus close to the values reported for the corresponding bulk material. However, the yield strength measured for the struts fixed in sockets was still much lower than that of the bulk material .…”

Section: Introductionmentioning

confidence: 99%

“…For the struts glued to the platelets, further improvements were reached by an estimation of the cross‐sectional area from the projected edge length, based on a statistical analysis, and by measuring strain by digital image correlation . While the strength values correlated well with the value of the corresponding bulk material, the average fracture strain (16%) of the AlSi7Mg0.3 struts in the as‐cast condition was 3 to 8 times higher than the values reported for a sand‐cast bulk alloy (2–6%) . Steel foam struts are much stronger than struts from Al‐ or Al‐alloy foams.…”

Section: Introductionmentioning

confidence: 99%

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Foams of Gray Cast Iron as Efficient Energy Absorption Structures: A Feasibility Study

et al. 2019

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Gray cast iron foams are produced using a reticulated polyurethane by using a modified investment casting process. To evaluate the attributes of the produced micro-geometries, foam segments and single struts are investigated by light and electron microscopy in 2D, and synchrotron micro-computed tomography in 3D. Mechanical properties are determined by macro/micromechanical testing and nanoindentation. In the microstructure of the gray cast iron struts, both flake-like coarse type A and locally fine undercooled type D graphite particles are observed. The distribution of the two graphite types is heterogeneous and is the likely cause for the large scatter of the mechanical properties of the single struts. The high graphite content and the resulting brittle behavior of the struts lead to strong serrations in the stressstrain curve of the foams with a negative effect on energy absorption. We found a relatively low energy absorption efficiency of below 50% as compared to 75% in 316L austenitic steel struts. The small specimen size results in scale effects which strongly influence the mechanical properties of the foams. Further improvement in the fabrication of gray cast iron foams is needed to tailor graphite distributions and optimize performance of cast iron-based foams.

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Micromechanical Characterization of Metal Foams

Jung¹,

Diebels²

2019

Adv Eng Mater

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Cellular materials such as foams, honeycombs, or auxetic structures are an interesting type of structural materials for lightweight constructions or dynamic energy absorbers. These microheterogeneous materials consist of a hierarchical structure. Foams can be separated into a macro scale, meso scale, and micro scale dealing with the entire specimen or component, individual pores, and individual struts, respectively. As a result, the macroscopic foam properties are strongly related to the mesoscopic and microscopic properties as a superposition of geometrical structural response and material properties. Whereas the geometry can be easily determined, e.g., by computer tomography measurements, the evaluation of real micro material properties of individual struts or cell walls is still a very challenging task. The material properties of these constituents of open‐cell or closed‐cell foams significantly differ from bulk material properties due to changes in boundary condition during production and different scaling effects, such as different surface‐to‐volume ratios of oxide layers or different cooling conditions due to less material in struts than in the bulk. However, the need for reliable micro material properties for the realistic forecast of macroscopic properties of components made of foam by numerical simulations makes the micromechanical characterization and testing of metal foams to an emerging field of research. The present contribution deals with the most relevant achievements in the field from the beginnings to the present day.

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Influence of heat treatments on the microstructure and mechanical behaviour of open cell AlSi7Mg0.3 foams on different lengthscales

Cited by 40 publications

References 26 publications

Investment Casting and Mechanical Properties of Open‐Cell Steel Foams

Investment Casting and Mechanical Properties of Open‐Cell Steel Foams

Foams of Gray Cast Iron as Efficient Energy Absorption Structures: A Feasibility Study

Micromechanical Characterization of Metal Foams

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