N. Iqbal, Delft University of Technology, Delft, Netherlands; T. Tinga, National Aerospace Laboratory Netherlands, Emmeloord, Netherlands; L. Katgerman, The Netherlands Institute for Metals Research, Delft, Netherlands
The mechanical properties of materials strongly depends on its microscopic structure. During the casting of Al-Si-Mg (A356) alloys, a small amount of grain refiners (TiB2, TiC etc) is added to reduce the aluminum grain size, while small traces of strontium modifies the eutectic silicon particle size and morphology. These changes in microstructure significantly improve the mechanical properties of the alloy. Experiments are conducted on the sand cast test rods using A356 alloy. The effects of grain refiner (Al-5Ti-1B) and modifier (Sr) additions are investigated separately and both together. The microstructural changes associated with additions have been studied by optical microscopy and scanning electron microscopy. The specimens cut from various locations of each cast, are tensile tested. The correlation between the mechanical properties and the microstructural changes due to grain refinement and Sr modification is established. The results indicate that the addition of both grain refiners and modifier have beneficial effects on the mechanical properties of A356 alloy. It is shown that the mechanical properties are affected by the specimen position in the cast bar. The responsible mechanisms are probed in terms of variation in microstructure and macrosegregation along the solidification path during casting.
The mechanical properties of materials strongly depends on its microscopic structure. During the casting of Al-Si-Mg (A356) alloys, a small amount of grain refiners (TiB2, TiC etc) is added to reduce the aluminum grain size, while small traces of strontium modifies the eutectic silicon particle size and morphology. These changes in microstructure significantly improve the mechanical properties of the alloy. Experiments are conducted on the sand cast test rods using A356 alloy. The effects of grain refiner (Al-5Ti-1B) and modifier (Sr) additions are investigated separately and both together. The microstructural changes associated with additions have been studied by optical microscopy and scanning electron microscopy. The specimens cut from various locations of each cast, are tensile tested. The correlation between the mechanical properties and the microstructural changes due to grain refinement and Sr modification is established. The results indicate that the addition of both grain refiners and modifier have beneficial effects on the mechanical properties of A356 alloy. It is shown that the mechanical properties are affected by the specimen position in the cast bar. The responsible mechanisms are probed in terms of variation in microstructure and macrosegregation along the solidification path during casting.
