Grain refinement and heat treatment of gravity die cast A356

The purpose of this investigation is to evaluate the effects of grain refiner TiCal315 (3%Ti, 0.15% C) and Al-5Ti-1B on the metallurgical properties of as-cast A356 gravity die castings as well as the improvement brought about by T6 heat treatment. The TiCal315 and Al-5Ti- 1B grain refiners were added separately into the A356 melt in different weight percentages of 0.25, 0.5, 0.75 and 1.0 to produce the gravity die casting samples. The geometry of the casting is designed to be cylindrical shape according to JIS H5202. The results show that TiCal315 is relatively more effective than Al-5Ti-1B to improve the tensile strength, hardness and elongation of A356 alloy by 10~20%. T6 heat treatment is confirmed to have more significantly improved the mechanical properties of A356 alloy compared to grain refinement. An Olympus imaging software was used to measure the average grain size of α-Al phase and the results do not show significant difference between TiCal315 and Al-5Ti-1B to grain-refine the A356 dendritic structures. The morphology of T6 heat treated A356 was changed where the irregular eutectic was converted into spherodized Si particles due to the solution treatment. This results in significant improvement in mechanical properties.