Producing metal matrix syntactic foams by pressure infiltration
TL;DR: In this paper, the authors present the possibility of syntactic foam production by pressure infiltration technology and investigate the effect of aspect ratio on the performance of synthetic foams in automotive technology or in aviation.
Abstract: This paper presents the possibility of syntactic foam production by pressure infiltration technology. Syntactic foams have low density and relatively high strength. Therefore they can be the material of many important parts in automotive technology or in aviation. The parameters of infiltration were studied and physical and mechanical investigations were performed. Microscopic investigations showed almost perfect infiltration at the applied infiltration pressure. The densities of the foams were significantly decreased. Low density ensures good specific properties and economical energy consuming in the case of moving the parts. Syntactic foams showed a plateau region in their upsetting diagrams and absorbed a high energy during upsetting. The effect of aspect ratio was also investigated. Specimens with higher aspect ratios showed lower peak stress, lower plateau level and higher modulus of elasticity.
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TL;DR: In this article, the compressive behavior of eight different metal matrix syntactic foams (MMSFs) is investigated and the results showed that the engineering factors such as chemical compositions of the matrix material, the size of the microballoons, the previously applied heat treatment and the temperature of the compression tests have significant effects on the compression properties.
Abstract: The compressive behaviour of eight different metal matrix syntactic foams (MMSFs) are investigated and presented. The results showed that the engineering factors as chemical compositions of the matrix material, the size of the microballoons, the previously applied heat treatment and the temperature of the compression tests have significant effects on the compressive properties. The smaller microballoons with thinner wall ensured higher compressive strength due to their more flawless microstructure and better mechanical stability. According to the heat treatments, the T6 treatments were less effective than expected; the parameters of the treatment should be further optimised. The elevated temperature tests revealed ∼30% drop in the compressive strength. However, the strength remained high enough for structural applications; therefore MMSFs are good choices for light structural parts working at elevated or room temperature. The chemical composition – microballoon type – heat treatment combinations give good potential for tailoring the compressive characteristics of MMSFs.
125 citations
Cites background from "Producing metal matrix syntactic fo..."
...For further details about the production process please refer to [4]....
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...In the MMSFs the porosity is ensured by the incorporation of ceramic microballoons [3, 4]....
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TL;DR: In this article, a combined experimental and numerical design of graded cellular materials for multifunctional aerospace application performed in the context of an integrated research project funded by the European Commission is presented.
87 citations
10 Oct 2013-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the microstructure and quasi-static compressive mechanical properties of Al-A206/Al 2 O 3 hollow sphere syntactic foams were investigated for foams with three different hollow sphere size ranges (0.212, 0.212 and 0.500), and three different conditions including As cast (F), T4 and T7.
Abstract: The microstructure and quasi-static compressive mechanical properties of Al-A206/Al 2 O 3 hollow sphere syntactic foams were investigated for foams with three different hollow sphere size ranges (0.106–0.212 mm, 0.212–0.425 mm, 0.425–0.500 mm) and three different conditions including As cast (F), T4 and T7. The peak strength, plateau strength and toughness of the foams were found to increase with increasing wall thickness to diameter ( t / D ) ratio. Since the t / D ratio was found to increase with decreasing sphere diameter, the foams produced with the smallest hollow spheres (0.106–0.212 mm) showed superior performance for the peak strength (F: 226 MPa, T4: 312 MPa, T7: 342 MPa), plateau strength (F: 190 MPa, T4: 269 MPa, T7: 269 MPa), and toughness (F: 59 J/cm 3 , T4: 78 J/cm 3 , T7: 88 J/cm 3 ). These properties were also found to generally increase with increasing matrix yield strength. The 0.212–0.425 mm T7 heat treated syntactic foams in this study exhibit the highest specific plateau strength (102 MPa-cm 3 /g) and the second highest specific energy absorption (41 J/g) of aluminum syntactic foams reported in literature for which comparable data is available.
81 citations
TL;DR: In this paper, a theoretical model reflecting the compressive strength of aluminum-cenospheres syntactic foams was developed with respect to the production conditions (compact pressure) of the green body.
75 citations
TL;DR: In this article, the effects of hollow sphere dimensions and foam microstructure on the quasi-static and high strain rate properties of the resulting foam were examined, and it was shown that the quasistatic compressive stress-strain curves exhibit distinct deformation events corresponding to initial failure of the foam at the critical resolved shear stress and subsequent failures and densification events until the foam is deformed to full density.
Abstract: Metal matrix syntactic foams are promising materials for energy absorption; however, few studies have examined the effects of hollow sphere dimensions and foam microstructure on the quasi-static and high strain rate properties of the resulting foam. Aluminum alloy A380 syntactic foams containing Al2O3 hollow spheres sorted by size and size range were synthesized by a sub-atmospheric pressure infiltration technique. The resulting samples were tested in compression at strain rates ranging from 10−3 s−1 using a conventional load frame to 1720 s−1 using a Split Hopkinson Pressure-bar test apparatus. It is shown that the quasi-static compressive stress–strain curves exhibit distinct deformation events corresponding to initial failure of the foam at the critical resolved shear stress and subsequent failures and densification events until the foam is deformed to full density. The peak strength, plateau strength, and toughness of the foam increases with increasing hollow sphere wall thickness to diameter (t/D) ratio. Since t/D was found to increase with decreasing hollow sphere diameter, the foams produced with smaller spheres showed improved performance. The compressive properties did not show measurable strain rate dependence.
70 citations
References
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TL;DR: In this article, hollow fly ash particles (cenospheres) were pressure infiltrated with A356 alloy melt to fabricate metal-matrix syntactic foam, using applied pressure up to 275kPa.
Abstract: Loose beds of hollow fly ash particles (cenospheres) were pressure infiltrated with A356 alloy melt to fabricate metal-matrix syntactic foam, using applied pressure up to 275 kPa. The volume fractions of cenospheres in the composites were in the range of 20–65%. The processing variables included melt temperature, gas pressure and particles size of fly ash. The effect of these processing variables on the microstructure and compressive properties of the synthesized composites is characterized. Compressive tests performed on these metal-matrix composites containing different volume fractions of hollow fly ash particles showed that their yield stress, Young's modulus, and plateau stress increase with an increase in the density. Variations in the compressive properties of the composites in the present study were compared with other foam materials.
258 citations
25 Jan 2005-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, synthetic foams were fabricated by liquid metal infiltration of commercially pure and 7075 aluminum into preforms of hollow ceramic microspheres, which exhibited peak strength during quasi-static compression ranging from −100 to −230 MPa, while dynamic compression loading showed a 10-30% increase in peak strength magnitude, with strain rate sensitivities similar to those of aluminum-matrix composite materials.
Abstract: Syntactic foams were fabricated by liquid metal infiltration of commercially pure and 7075 aluminum into preforms of hollow ceramic microspheres. The foams exhibited peak strengths during quasi-static compression ranging from −100 to −230 MPa, while dynamic compression loading showed a 10–30% increase in peak strength magnitude, with strain rate sensitivities similar to those of aluminum–matrix composite materials. X-ray tomographic investigation of the post-compression loaded foam microstructures revealed sharp differences in deformation modes, with the unalloyed-Al foam failing initially by matrix deformation, while the alloy–matrix foams failed more abruptly through the formation of sharp crush bands oriented at about 45° to the compression axis. These foams displayed pronounced energy-absorbing capabilities, suggesting their potential use in packaging applications or for impact protection; proper tailoring of matrix and microsphere strengths would result in optimized syntactic foam properties.
212 citations
TL;DR: In this paper, the authors investigated the mechanical response of a family of ceramic microballoon reinforced aluminum matrix composites under both uniaxial compression and constrained die compression loadings.
144 citations
"Producing metal matrix syntactic fo..." refers background in this paper
...Kiser et al. (1999) investigated the mechanical response of syntactic foams produced by vacuum assisted casting....
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TL;DR: In this paper, syntactic foams were fabricated by pressure-infiltrating liquid aluminum (commercial purity and 7075-Al) into a packed preform of silica-mullite hollow microspheres.
141 citations
"Producing metal matrix syntactic fo..." refers background in this paper
...This reaction was also reported by Balch and Dunand (2006) [6]....
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31 Mar 1998-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors used Young's and Washburn equations to calculate an effective wetting angle between molten pure aluminum and fly ash using Young's equations and showed good infiltration except for regions between contacting cenospheres.
Abstract: Beds of nickel coated and uncoated cenosphere fly ash can be successfully infiltrated by molten aluminum under very low pressures. The density of the resultant composite is ≈1.4 and 1.2 g cm−3 respectively, compared to 2.68 g cm−3, the density for aluminum. The threshold pressure was found to be between 20.68 and 27.58 kPa for infiltration of molten pure aluminum into uncoated fly ash, and around 6.7 kPa for Ni-coated fly ash. These data were used to back calculate an effective wetting angle between molten pure aluminum and fly ash using Young’s and Washburn equations. The average value of the wetting angle calculated for uncoated fly ash is 111°. The microstructures and chemical composition of the composites made with coated and uncoated fly ash were studied using optical and scanning microscopy; they show good infiltration except for regions between contacting cenospheres. They also show transport of nickel from the bottom to the top of the sample when nickel coated particles were used.
130 citations
"Producing metal matrix syntactic fo..." refers background or methods in this paper
...The same was done by Rohatgi et al. (1998), but they defined an effective distance between the microballoons [3]....
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...With these data one can express the threshold pressure [9]. p = 2σl/g cos θ rh = 12λVmbσl/g cos θ (1 − Vmb) D (2) Rohatgi et al. (1998) also use the Young-Laplace equation, but they define an other radius (re), which expresses the effective distance between the microballoons [3]....
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