Light‐Metal Foams—History of Innovation and Technological Challenges

Abstract

The history of metallic foams and the key innovations that have led to the variety of processing methods known today are reviewed. It is evident that the idea of foaming metals is very old and that most of the techniques used today have been proposed already in the 1950s. The most important milestones in the development of foaming technologies and the some of the attempts to commercialize metal foams are reviewed.

Effect of CaCO₃ Foaming Agent at Formation and Stabilization of Al-Based Foams Fabricated by Powder Compact Technique

“…Contact angle measured for Al 3 Ti by sessile drop method decreases as holding time increases and, then, arrives stable equilibrium value (θ = 99 ) at holding time about 10 min and longer, as can be seen in Fig. 8.…”

“…After this the above foams runs out the expansion and, then, decay gradually with increasing the temperature up to 700 C although release of hydrogen from TiH 2 was still in progress. 6,8) Unlike the above both carbonate kind of foam of ZAM alloy (4) and that of Al added with complex foaming agent (2) continue to expand up to the maximum values as the temperature increases up to 700 C. Finally, maximum expansion of the foams created by CaCO 3 foaming agent (2,4) is rather high in comparison with those indicative of hydride kind of foams (1,3). Moreover, the foams (2,4) keep maximum expansion for about 200 s and longer whereas hydride kind of foams (1,3) keep maximum height less than for 50 s.…”

“…27) Nevertheless, other micrometre-sized particles detected on the cell surface and in the cell wall material are rather different for studied kinds of foams. Foreign particles of partly converted TiH 2 rounded by Al 3 Ti layers (A) and its reaction products such as Al 3 Ti particles (B) as well as traces of (Al+Al 3 Ti) eutectic domains (C) are randomly scattered in the cell wall material of hydride kind of Al-foams, as can be seen in Figs However, cell wall microstructure of carbonate kind of ZAM alloy foam was found to be rather different. 7) Particles of CaO/CaCO 3 (D) accumulate preferably within the eutectic domains of redundant phase (F) enriched by low-melt alloyed elements, as shown in Fig.…”

“…However, despite a number of manufacturing processes developed for production of Al-foams the last ones contain economical and technical limitations. As applied to the frequent use methods employed for production of machinable Al-foams, which are based on handling of a melt and powder compact technique, [1][2][3] economical limitation arises due to the employment of a rather expensive titanium hydride (TiH 2 ) as foaming agent. Moreover, aluminium foams still suffer from non-uniformities and other structural de ciencies.…”

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

“…Comprehensive details of distinctive features required for compres- 4) energy absorption up to densification, 5) calculated over theoretical relations [9] the same as it was fulfilled previously [13,14]. sion tests of porous Al and Al foams was done on the base of newly developed Standard ISO.…”