Study On Counter-gravity Infiltration Casting Fabrication And Properties Of Al₂O₃k/Al Porous Composites And Sandwich Panel

Owing to its structure and function properties, porous aluminum has a wide range of applications in automotive, construction and aerospace field. The Al2O3k/Al porous composites and its sandwich panel were prepared by the counter- gravity infiltration casting method, and deep and systemic research on the mechanical properties of compressive property Al2O3k/Al porous composites and sandwich panel were carried out. The following conclusions were obtained in this master's thesis:(1) Al2O3k/Al porous composites were fabricated by the counter-gravity infiltration casting using 6063 alloy as matrix metal, alumina-hollow sphere as pore-forming particles. The results show that the infiltrating effect of Al2O3k/Al porous composites was improved by increasing the diameter of hollow-sphere, increasing the pre-heating temperature of hollow sphere and the temperature of the aluminum melt, raising filling pressure, prolonging holding time, selecting from top to bottom cooling method and adding active element Mg.(2) The quasi-static compressive properties of Al2O3k/Al porous composites were studied. The results are as follows:the quasi-static compressive stress-strain curves of Al2O3k/Al porous composites include three stages. The main failure characteristics are strain localization and the failure occurred layer by layer. The yield strengths of Al2O3k/Al porous composites increase with decreasing the diameter of Al2O3-hollow sphere and void content, but increasing void content is good for prolonging the collapse plateau region. Fitting coefficients K were calculated by strength fitting calculation in Ashby formula, and the results are K>0.75.(3) The energy-absorption characteristic of Al2O3k/Al porous composites was studied. The results are as follows:the energy absorption capacities of Al2O3k/Al porous composites mainly lie on the yield strength, the length of the collapse plateau region and the strain hard exponent. The energy absorption efficiencies are dependent on the ratio of upper yield strength to lower yield strength, the ratio of the yield strain to the densification strain, and the ratio of the elastic module to the strain hard exponent. The energy absorption capacities would increase with decreasing the diameter of Al2O3-hollow sphere and void content, increasing strain rate. The energy absorption efficiencies are independent of the diameter of Al2O3-hollow sphere, and it increase with increasing void content and decreasing strain rate.(4) The sandwich panels of Al2O3k/Al porous composites were prepared. The three-point bending P-δcurves of Al2O3k/Al porous composites sandwich panels have the features of typical sandwich panels. It is found that the sandwich panels of Al2O3k/Al porous composites have more excellent three-point bending properties. The main failure modes of Al2O3k/Al porous composites sandwich panels include the core-material shear crack and the panel bending, and there is no crack appearance in interface.