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Aluminum (Al) foam does not recover to its initial shape once it absorbs shock energy and deforms. In this study, the refoaming of deformed A6061 Al foam was attempted. Closed-cell Al foam fabricated by a precursor foaming process was reproduced to obtain a similar closed-cell Al foam by subjecting it to the precursor foaming process again. It was...
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Precursor foaming is one of the processes used to produce aluminum (Al) foam. This process fabricates a foamable precursor by mixing a blowing agent powder with solid Al. Then, the fabricated precursor is foamed by heat treatment. In this study, the process of simultaneously fabricating and foaming the precursor was attempted by friction stir weldi...
The use of multi-materials, in which a wide variety of materials are used in the appropriate places, is being promoted to reduce carbon dioxide emissions. In the multi-materialization of automobiles, steel-aluminum joints are widely used. Friction stir welding (FSW) is used for joining steel and aluminum. Because of the solid state and short joinin...
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... In the case of ADC12, the solidus temperature is 515 • C and the liquidus temperature is 580 • C [43]. Because the heating temperature of the aluminum foam sheet in this study was sufficiently lower than the foaming temperature, no shape changes in aluminum foam, such as pore deformation or re-foaming behavior [44,45], were observed. ...
Aluminum foam has relatively low tensile and flexural strengths because it is composed of many pores with thin cell walls. One method of strengthening aluminum foam is to fabricate a composite material with a dense lightweight resin. In this study, the fabrication of composite materials by directly printing resin on an aluminum foam surface using a 3D printer was attempted. The resin was directly printed on both heated and unheated aluminum foam. It was shown that composite materials consisting of aluminum foam and resin can be fabricated by directly printing resin with a 3D printer on both heated and unheated aluminum foam. The resin was softened during the printing process in the case of directly printed resin on heated aluminum foam, allowing more resin to penetrate into the pores than in the case of directly printed resin on unheated aluminum foam. In addition, it was shown that resin can be directly printed on the aluminum foam with a high bonding strength, as a large amount of resin penetrated into the pores, resulting in an anchor effect. That is, composite materials consisting of aluminum foam and arbitrary-shaped resin with relatively high bonding strength can be fabricated when a large amount of resin is allowed to penetrate into the pore.
... These results show that the press forming of aluminum foam immediately after foaming the precursor can be used to shape aluminum foam while retaining its pores. One reason for the retention of pores without their collapse is that the decomposing TiH2 continues to release gas throughout the foaming process according to the works in [24][25][26][27]. Therefore, the release of gas continues until solidification, which maintains the inner pressure of the pores, resulting in them keeping their shape even during press forming. ...
Forming aluminum foam to the desired shape while retaining its pore structures is essential for manufacturing aluminum foam products. Recently, a press forming process for aluminum foam that is performed after precursor foaming but before solidification has been proposed. In this study, to track individual pores throughout press forming immediately after foaming, X-ray radiography inspection was applied. A thin precursor was used, and foaming was constrained to the X-ray transmission direction. It was shown that, although some pores coalesced with other pores, the pores did not collapse during press forming. In addition, the porosity of aluminum foam evaluated from X-ray transmission images was constant during press forming. Some pores retained their shape during press forming but their position was changed by the material flow generated by press forming. These results show that by press forming before the solidification of aluminum foam, aluminum foam can be shaped without the collapse of pores.
Porous aluminum, which has many pores inside, is lightweight and has high shock absorption properties. However, once porous aluminum is impacted and deformed, the cell walls are collapsed and difficult to reuse. In this study, we attempted re-foaming of deformed porous aluminum using the undecomposed foaming agent remained during the porous aluminum fabrication process. In our previous study, it was found that porous aluminum can be re-foamed by compressing and densifying with FSP before optical heating. In this study, we attempted further foaming of refoamed porous aluminum by optical heating after densification by compression and FSP. The amount of foaming gradually decreased with each repeated foaming, and the pore structures were not the same as that of the initial foaming, but further foaming was achieved after re-foaming. From the XRD analysis, it was observed that the undecomposed foaming agent remained after re-foaming.
The shaping of aluminum foam with high productivity is indispensable for the wide use of lightweight aluminum foam in various industrial fields. The precursor foaming process is one of the industrialized manufacturing processes of aluminum foam. Recently, a process for the press forming of aluminum foam during foaming of the precursor has been developed. In this study, pores during press forming were observed nondestructively by X-ray radiography. The behaviors of pores during press forming while foaming the precursor and during press forming at room temperature after the precursor had been foamed and solidified were compared. It was shown that the pores during press forming during foaming can be continuously observed nondestructively by X-ray radiography. Pores in the aluminum foam only moved and did not collapse during press forming while foaming, which indicated that ductile material flow occurred during press forming. In contrast, no flow of pores in the aluminum foam was observed during press forming of the aluminum foam at room temperature, but the cell walls collapsed and the density of the aluminum foam increased, which indicated that brittle fracture occurred during press forming. From X-ray computed tomography (CT) images of the samples, the pore structures of aluminum foam press-formed during foaming were similar to those of the aluminum foam before press forming. In contrast, the pore structures of the aluminum foam press-formed at room temperature were considerably different from those of the aluminum foam before press forming. Consequently, it was demonstrated that the press forming of aluminum foam during foaming can be used to shape aluminum foam without affecting the pore structures.
Alumina hollow spheres with a diameter range of 1–2 mm were filled in 6061 Al alloy by gravity infiltration casting to synthesize Al-matrix syntactic foams. The effects of infiltration temperature and heat treatment on microstructure, compressive properties, and energy absorption properties of the syntactic foams were studied. The results show that high quality syntactic foams could be synthesized in the infiltration temperature range 770–830 °C and the particles seamlessly bonded with the matrix. The average density and porosity of the syntactic foams were around 1.66 g/cm3 and 37.47%, respectively. The highest energy absorption capacity and specific energy absorption of the as-cast syntactic foams occurred at infiltration temperature 770 °C, reaching 41.11 MJ/m3 and 23.63 kJ/kg, respectively, while these parameters for the heat-treated samples showed the maximum values for the solution-aging treated samples, reaching 48.92 MJ/m3 and 31.36 kJ/kg respectively. Extensive literature survey is presented in this work by extracting the compressive properties of a variety of Al-matrix syntactic foams and comparing them with the results obtained in the present work. It is observed that the syntactic foams synthesized by gravity infiltration method equal or exceed the properties demonstrated by many Al-matrix syntactic foams synthesized by other methods reported in recent years. As a major advantage, the gravity infiltration method can be scaled up to industrial production level.
