Produção e análise de espumas sintáticas via tixoinfiltração da liga de alumínio aa6351 em balões fly ash

Abstract

Cellular metals have demonstrated great potential for several applications in mobility engineering. They allow different characteristics in a single material, such as low density with high specific rigidity, energy absorption capacity in impacts and vibration dampening, and even thermal and acoustic insulation. In this sense, this work aims to develop a methodology for syntactic foams with an aluminum matrix (Aluminum Matrix Syntactic Foam, AMSF) production, a subdivision of cellular metals wherein the pores in the metallic matrix come from hollow particles, with subsequent analyses of the material's morphological, metallurgical, physical and mechanical characteristics. For the production of AMSF, Fly Ash balloons of three different meshes were positioned between two AA6351 aluminum alloy discs inside a steel mold, which after undergoing a controlled partial melting treatment up to 645 ºC and approximately 80% of liquid fraction, according to Differential Exploratory Calorimetry (DEC) and thermodynamic simulations (Thermo-Calc). Then, the alloy was driven to infiltrate the preform containing loose Fly Ash balloons through the action of a hydraulic press. The manufactured composite was a sandwich panel with an AMSF insert whose morphology was investigated by X-ray computed microtomography and optical and electronic microscopy, and mechanical properties evaluated by quasi-static compression tests and Vickers micro-indentation hardness tests. Therefore, it was possible to observe that the manufacturing process was suitable for the production of AMSFs using the balloons of the three different meshes. However, those of mesh 60 stood out for allowing thicker foam layers, about 7.5 mm, adding 5% by mass of balloons concerning the upper disk portion of the aluminum alloy. However, because of their structural integrity characteristics, syntactic foam with balloons from mesh 60 was the main focus of the analyses. Therefore, with a homogeneous distribution of balloons in the matrix and with average values of 42% porosity, refined microstructure with 65 HV100 hardness, 37 MPa offset strain and 18 MJm-3 energy absorption (W) with 25% deformation, we concluded that the AMSFs production route by infiltration was successful. Finally, syntactic foams with an aluminum matrix already studied had entirely hollow balloons and no internal structure, unlike those used in this work, whose balloons had inner walls and fibers that enabled higher compression resistance. The inner walls and fibers allowed internal voids to remain in the composite structure, even in high deformations.