Sustainable Production of Powder Metallurgy Aluminum Foams Sintered by Concentrated Solar Energy

Abstract

Porous aluminum foams were successfully fabricated following the space-holder powder metallurgy method with a solar sintering stage. Al foams with porosities of 50, 60, and 70 vol.% were sintered in a low-cost Fresnel lens. Green parts were prepared using aluminum powder as the main metallic material and saccharose as a soluble space-holder. The dissolution stage was designed for each foam and required longer periods of time, between 8 and 32 h, as the design porosity increased. Brown parts were fully sintered by concentrated solar energy at a lower temperature (500 °C) and for shorter times (12–20 min) than those required by conventional sintering techniques (640 °C, ~9 h). The evaluation of density and the characterization of pore size and distribution in the sintered foams was carried out. All obtained foams were stable and presented a homogeneously distributed porosity, very close to the design porosity, with differences lower than 2.1 vol.%, and with approximately half being characterized as open porosity. Moreover, the solar sintered foams presented a high quality, and similar or even greater mechanical properties (such as compressive strength and impact energy absorption) than those achieved by conventional techniques. Foams with 50 vol.% of porosity exhibited the best mechanical behavior, in terms of impact-energy absorption (24.42 MJ/m3) and compressive strength (27.4 MPa).