Modeling of non-Equilibrium Solidification of Aluminium-Copper Alloys

Knowledge about the non-equilibrium phase diagram is necessary to model the microsegregation in practical situations. Therefore the aim of this research is theoretical analysis of the phase diagram and diffusion coefficient for calculation of microsegregation. In order to do this, the non-equilibrium solidification condition was simulated by increasing the vacancy content to a non-equilibrium value according to the certain cooling rates. Aluminium rich part of the Al-Cu phase diagram was recalculated and the effect of these excess vacancies was incorporated during calculations. The effect of excess vacancies on diffusion coefficient was also considered. Al-Cu alloys were solidified with different cooling rates and the concentration profiles in the primary phase were measured experimentally. These concentration profiles were also calculated by three sets of input data; i.e. equilibrium phase diagram and diffusion data, non-equilibrium phase diagram and equilibrium diffusion coefficient, and non-equilibrium phase diagram and diffusion data. The results show that by modifying the phase diagram, the calculated results have better consistency with the experimental results, but still not to a satisfactory limit. However, by correcting diffusion coefficient, the modeling results show much better correlation with the experimental results

Keywords:

Al-Cu Binary Alloys , Cooling Rate , Microsegregation , Phase Diagram , Diffusion Coefficient