9th International Aluminium Symposium, İstanbul, Turkey, 10 - 11 October 2019, pp.256-260
As with all metallic materials, the mechanical properties of aluminium alloys are directly related to the microstructure. In both aluminium wrought and casting alloys, it was observed that mechanical properties increased due to fine and uniform microstructure during the casting process by applying grain refining process. By virtue of the fine and equiaxed microstructure, the material shows high strength and ductility. For these reasons, grain refinement is widely applied in the casting of aluminium alloys. In the literature; grain refinement processes can be realized with different methods. These techniques can be listed as; thermal, chemical and dynamic methods. In this study, orbital shaking method which lays among the dynamic methods has been investigated. Within the scope of this study, as an alternative way to the traditional mechanical vibration method; A356 aluminium casting alloy was cast by lost foam casting method (LFC) with the orbital shaking. In the experiments, the effects of the shaking rate were investigated for resulted casting parts. Expandable polystyrene (EPS) patterns (170x50x40 mm) with the density of 10 kg/m-3 were used in the moulding process. The castings were performed at 720 °C for 50, 100, 150 and 200 rpm of orbital shaking rate. The reference sample was cast at static state at the same temperature. The microstructure samples were removed from the edges and the centre parts of these samples. Metallographic examinations were carried out via image analyzer assisted optical microscope by means of calculating shape factor, grain size, and SDAS (secondary dendrite arm spacing). In addition, the densities of the samples were measured for the porosity evaluation by Archimedes' principle. The hardness values of the samples were calculated by Brinell hardness method.