The effects of metalic sodium and antimuan addition on microstructure in al-si alloy

Al-Si alloys are one of the most common foundry alloys due to their low density, excellent castability, high strength-to-weight ratio, corrosion and wear resistance, pressure tightness and good weldability. Applications of these alloys have included automotive sylinder heads, engine block, aircraft compenents and pipe fittings. The mechanical properties of alüminium-silicon alloys are related to the shape, size and distribution of eutectic silicon. Coarse eutectic silicon with lamellar shape and sharp corners reduces the mechanical properties. It has been reported that the addition of Sb into Al-Si alloys only causes a refinement in the plate-like silicon structure. However, modification of the Al?Si eutectic from a flake-like to a fine fibrous silicon structure can be achieved by the addition of Na and Sr.In this study, the effects of Sb and metallic sodium on the silicon in Al-9.5%Si alloy have been examined by using metallographic observation, quantitative measurement and thermal analysis techniques. Therefore, various amounts of Sb (0,025 ?0,050 ?0,075 ? 0,1- 0,2-0,5 in wt%) and metallic Na (0,012-0,025-0,05-0,075-0,1-0,15-0,175 in wt%) were added into liquid of Al-9.5%Si alloy.The results obtained show the following;vii1- The addition of 0,1%Sb into Al-9.5%Si alloy refined silicon,2- The addition of 0,1%Sb into Al-9.5%Si alloy decreased the temperature by a factor of 6oC,3- The addition of 0,1%Sb caused a 69% reduction in the Interparticle spacing,4- The addition of 0.1%Na changes eutectic silicon from coarse plate-like to a fine fibrous structure,5- The addition of 0,1%Na into Al-9.5%Si alloy decreased the eutectic temperature by a factor of 10oC,6- The lowest interparticle spacing was obtained with addition of 0.1%Na,7- The addition of 0,1%Na and 0.1%Sb into Al-9.5%Si alloy produced fibrous eutectic silicon. But, fibrous eutectic silicon started to coarsening.Science Code : 912.1.080Key Words : Al-Si alloys, antimuan, metallic sodium, modification,Page Number: 89Adviser : Prof. Dr. Kadir KOCATEPE