Abstract
In this research, syntactic foams including Al-7075 matrix and 2-4 mm low-cost pumice particles were manufactured via a novel casting method called as sandwich infiltration. According to physical evaluations, thanks to extremely porous structure of pumice, density values of the fabricated foams varied between 1.42 and 1.61 g/cm3. Porosity values were between 40.62% and 47.39%. Microstructural observations showed that there was a perfect infiltration between Al matrix and pumice particles because of correct process optimization (process pressure of 0.1 MPa, matrix melting temperature of 720°C and filler pre-temperature of 500°C). Furthermore, T6 treatment was applied to samples to comprehend effect of the aging on mechanical properties. The results indicated that there was an affirmative relation between the heat treatment and quasi-static compressive properties of the fabricated foams. The highest compressive strength, plateau stress and energy absorption values were measured as 64.4 MPa, 74.3 MPa and 34 MJ/m3 for heat treated samples. It was also observed that although the highest energy efficiency of 0.89 was calculated for heat treated sample, there was no relation between the heat treatment and efficiency. As for failure modes, as-cast samples exhibited ductile barreling characteristic whereas T6 treated foams indicated brittle v-shape fracture.
Highlights
Metal matrix syntactic foams (MMSFs) have come into the forefront in recent times because of their superior compressive properties, low densities, good strength to weight ratios and perfect energy absorption abilities[1,2]
While aluminum, magnesium, steel, titanium and zinc alloys are often preferred as matrix materials[4,5,6,7], thin walled hollow ceramics and porous fly ash cenospheres are used as fillers[8,9,10]
Since spherical hollow ceramic and glass fillers have high cost and require complex manufacturing methods, researchers have inclined to cheap alternatives like expanded perlite (EP) which is an extremely light volcanic glass and fly ash cenospheres which are the product of coal burning[11,12]
Summary
Metal matrix syntactic foams (MMSFs) have come into the forefront in recent times because of their superior compressive properties, low densities, good strength to weight ratios and perfect energy absorption abilities[1,2]. These advanced materials have been thoroughly investigated by certain researchers to explore their mechanical, structural and thermal features. While aluminum, magnesium, steel, titanium and zinc alloys are often preferred as matrix materials[4,5,6,7], thin walled hollow ceramics and porous fly ash cenospheres are used as fillers[8,9,10]. Since spherical hollow ceramic and glass fillers have high cost and require complex manufacturing methods, researchers have inclined to cheap alternatives like expanded perlite (EP) which is an extremely light volcanic glass and fly ash cenospheres which are the product of coal burning[11,12]
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