Ti Grain Refinement Myth and Cleanliness of A356 Melt

Abstract

Grain refinement of cast alloys provides several advantages such as establishment of finer dendritic structure, lowered porosity due to increased feeding, and thereby higher mechanical properties are reached. For Al–Si alloys, Ti is the preferred; however, Ti has the tendency to sink to the bottom of the crucible due to density difference. In this work, this phenomenon was used to evaluate the correlation of Ti nucleation on bifilms and thereby sedimenting the defects to clean the melt. Primary and secondary A356 alloys were used. After grain refinement addition, samples were collected every 10 min to investigate the change in melt quality. Sand and die moulds were used. Tensile samples were produced for mechanical characterisation. Step mould was used to check the microstructural changes. Reduced pressure test was used to quantify melt cleanliness. It was found that melt quality was increased by duration. Mechanical properties were increased regardless of the microstructure.