Processing of Shape Memory CuZnAl Open-cell Foam by Molten Metal Infiltration

Abstract

Foams and other highly porous materials with a cellular structure are known to have many interesting combinations of physical and mechanical properties. In addition, foaming of shape memory alloys (SMA) greatly improves the set of application possibilities. In this work an open-cell metal foam of a CuZnAl SMA is presented. This foam was produced through a recently proposed process, which consists mainly in molten metal infiltration of a bed of silica-gel particles and the subsequent use of hydrofluoric acid (HF) as solvent. The results showed that very regular open-cell foams could be obtained, having an almost spherical cell morphology and relative densities of approximately 0.3. Microstructural and compositional analyses on foamed specimens showed uniform microstructure of ligaments and the absence of SiO 2 interaction with the metal. In this way the possibility of foaming CuZnAl system through the proposed low-cost process was clearly demonstrated.

Cyclic pseudoelastic behavior and energy dissipation in as-cast Cu-Zn-Al foams of different densities

“…The resulting alloy specimens weighted around 80 g. By using these alloys as starting materials, foams were obtained by the method described in detail in Ref. [21,23]. Briefly, the alloys were re-melted in an open induction furnace using pure carbon crucibles.…”

“…Indeed, several studies aimed at finding suitable alloy candidates for producing structural SMFs are reported in the literature. The most promising involve the use of Fe-based [19] and Cu-based SMAs [20,21]. Among them, Cu-Zn-Al SMAs are of particular interest.…”

“…The alloys melting temperatures are lower than in the case of Ni-Ti, allowing for different foaming procedures like, for example, liquid phase processing. Recently, a method useful to synthesize Cu-Zn-Al SMFs has been reported [21,23]. It consists of the infiltration of molten metal into a bed of silica particles, which are then leached through a suitable chemical attack.…”

“…The method enables to obtain foams of different densities, pore morphology and mean pore size. The obtained foams reported by Castrodeza et al [21] need a thermal treatment due to the fact that the as-cast foam contains a mixture of a and b-phases. On the contrary, the foams reported by Bertolino et al [24] present only a b-phase in the as-cast condition and display good pseudoelastic properties without the need of performing special thermomechanical treatments [24].…”

Fiber Laser Welding of Copper based Open Cell Foams

“…One of the most innovative foaming process concerns the infiltration of leachable solid particles in the molten material [4][5][6]. In open literature, the most studied metallic foams, obtained by liquid infiltration of leachable space holders, are usually Al or Cu based alloys because these offer lightness, high stiffness, good thermal stability and quite low manufacturing cost [4].…”