Daynamic nature of diffuson during solidification

Some of the mechanisms which determine the extent of microsegregation during solidification of metallic alloys are based on the diffusion in the solid, so deep knowledge about diffusion is essential for studying the microsegregation. The aim of this research is therefore to elucidate the nature of diffusion during the solidification. For this purpose, Al-4.8 wt% Cu alloy was selected as model alloy. Solidification tests were carried out using a differential thermal analysis (DTA) furnace capable of quenching samples during solidification. Cooling rate was selected as 5 K/min and samples were quenched from predetermined temperatures during the solidification. Copper concentration profiles in the primary phase were measured by scanning electron microscope (SEM) equipped with an energy dispersive spectroscopy (EDS) detector. The concentration profiles were also calculated by numerical modeling and compared to the experimental profiles. According to the results it concluded that the diffusion coefficient has higher values than the tabulated ones at the begging of solidification. The results were discussed according the current theory of solidification.

Keywords:

Solidification , Microsegregation , Phase Diagram , Diffusion Coefficient , Vacancy