Papers by Keyword: Metallic Foam

Abstract: In the paper are presented the techniques for obtaining metallic foams based on copper. The permeability of them is described. The metal foams in this case are made from a mixture of copper and NaCl in well-established proportions (20%, 30% and 40% Cu), pressed (the mixture) in mould and sintered at temperatures of 780°C and 830°C. Proper knowledge’s of the permeability (K) are important and should be defined properly [1]. The present study was carried out to have an understanding the influence of different permeability values for different NaCl concentrations in the foams. The necessary equipment was adapted for this purpose. The permeability values obtained for this reason was correlated with the pore size and number of pores per square centimeter. With the increasing of pore diameters and copper proportion the increasing of permeability of metallic foams was also measured.

Abstract: Metallic foam is currently one of very active research topics in worldwide research communities, owing to its high potential to be employed in numerous industrial applications. Around 150 institutions are reported to be working in metallic foam research and development. In Thailand, it has been a research focus of universities and research institutes for many years. Most of them involve fabrication, characterization, improvement of metallic foam quality and process, and development of novel metallic foams. The majority of metallic foam research is conducted at Chulalongkorn University. The present article reports a review of metallic foam researches in Thailand.

Abstract: In this work we shows procedure for new biomaterial - void metal composite (VMC) formation. We used a quasi-spherical sucrose crystals as a space holder material. In the process, titanium powder (different particle sizes) and sucrose were mixed together and uniaxially pressed to make a green compacts. In the next step the sucrose crystals were dissolved in water, leaving open spaces surrounded by metallic scaffold with different porosity (50 – 70%). Such prepared titanium scaffold was dried and sintered in vacuum. The foams morphology was investigated by SEM and CT. The corrosion tests of the as prepared materials were performed in Ringer`s solution using cyclic polarization measurements. We shows that Ti scaffolds prepared by using sucrose as a space holder have corrosion resistance comparable to bulk microcrystalline titanium.

Abstract: Based on the obtained experimental results, the features of stress-strain behavior of the metallic foam were discussed firstly in this paper. Then, in the framework of 2M1C visco-plasticity constitutive model, a cyclic constitutive model was proposed to simulate the stress-strain responses under monotonic and cyclic compression. In proposed model, plastic strain is divided into two parts, i.e., plastic strain of matrix metal and plastic strain of voids structure, which are associated with relative density. Additionally, a kinematic hardening rule of yield surface center is used to describe ratchetting effect during cyclic loading. The simulated stress-strain responses of aluminum foam are in a good agreement with the experimental ones.

Abstract: Open-cell Al foam has outstanding properties which are suitable for functional applications. However, a major drawback for widespread employment of Al foam is its high relative cost which can be several times higher than conventional metals. To reduce the cost, a recycled material waste is constructively used instead of expensive base metal. The present study aims to fabricate economical open-cell Al foams using AC8A alloy scrap from lathe machines. The Al foams were fabricated through pressure infiltration casting process at which the cellular pattern was made from commercial reticulated open-cell polyurethane foams with the pore size of 12 ppi. The compressive strength and microhardness of scrap-recycled Al foams are higher than those of pure Al foam. The increase in foam mechanical properties resulted from the change in foam microstructure as the formation of Si hard phase in Al matrix. The strength and microhardness of the foams increase with increasing scrap contents.

Abstract: Mg-Ca-Zn alloy metallic foam has been recently recognized as biodegradable implant. In this present work, the characteristics of Mg-Ca-Zn alloy metallic foam which made by foaming of powder compact based on Mg-Zn-CaH₂ system were investigated. Mg-Zn-CaH₂ powder with nominal compositions of 97.5 weight % Mg, 2 weight % Zn, 0.5 weight % CaH₂ and 96.8 weight % Mg, 2 weight % Zn, 1.2 weight % CaH₂ were prepared by dry milling process for 6 h and characterized by differential thermal analysis (DTA). The prepared powders are pressed for 6.5MPa at room temperature and sintered for 2 h at various temperatures of 350 °C and 600 °C. The alloys were analyzed by x-ray diffraction and scanning electron microscope (SEM). The results indicated that addition of calcium hydride as blowing agent affects phase formation of Mg₂Ca and Mg₂Zn₃, sintering temperature and grain refining of Mg-Ca-Zn alloy.

Abstract: Authors of the paper present structures of composite metallic-ceramic foams (Al11SiC) of characteristic internal composition, produced at Maritime University of Szczecin. Diversification of pore size and structure of composite walls is present. The foams are manufactured by injection of a gas into a liquid composite using a special device, which allows to realize the foam manufacturing process in a continuous manner. This device also allows to control the parameters of the foaming process, which results in possibility of influencing, among other things, the size and the size distribution of formed gas bubbles. After manufacturing foams with both homogeneous and diversified gas pores, basic mechanical properties of these foams were examined, revealing a connection with their structure. Possibilities of applied research methods, utilizing a microscope and a tomograph, were also presented. Methods using computer image analysis were selected for the structure description.

Abstract: Explored the influence of pore structure of foam metal material on mechanical behavior of fracture. Discuss fracture toughness of several different micro geometric structure of foam metal material with finite element method. The author's calculations showed, microstructure and loading mode has an important effect on the fracture toughness of the foam metal material. due to ignoring the effects of cell structure on the mechanical properties of materials, the classic fracture toughness criterion -crack tip opening displacement (COD) is incomplete, it would be more efficient to take opening displacement change rate of the crack-tip as the parameter to characteristic the metallic foam material fracture toughness.

Abstract: A discretization elastic-plastic material model was used for simulating the shock waves transmission within metallic foams. The density heterogeneity of metallic foams was considered. Several types of aluminum foams are studied on the transmission of displacement and stresses wave under impact loading. The results reveal the characteristics of compressive wave propagation within the metal foams. Under low impact pulses, considerable energy is dissipated during the progressive collapse of foam cells, and then reduces the crush of the objects. When the pulse is high sufficiently, on the fixed end of foam, stress enhancement may take place, where high peak stresses usually occur. The magnitude of the peak stress depends on the relative density of foams, the pulse loading intensity, the pulse loading duration as well as the density homogeneity of foam materials. This research offers valuable insight into the reliability of the metal foams used as vehicles and protective structure.

Abstract: The sintering and dissolution process (SDP), in which NaCl is used as space holder, was used to produce open-cell Ag foams with various pore sizes. The content, size and shape of NaCl particles dictate the pore architecture of the foams. The yield strength of Ag foams decreases with increasing porosity. Of equivalent porosity, the yield strength of the foams with larger pore size is also higher than the foams with smaller pore size.