Nucleation kinetics during the solidification of aluminum alloys

The nucleation kinetics of individual grains during solidification of an aluminium alloy are experimentally investigated by X-ray diffraction at a synchrotron source. The investigated aluminium alloy contained solute titanium along with micrometer size TiB2 particles, which act as substrates for heterogeneous nucleation of aluminium grains during solidification. The nucleation rate of aluminium grains during solidification is measured by different cooling rates ranging from 1 to 40 K/min. The measurements indicate that for the continuous cooling, the nucleation rate strongly decreases with time. The nucleation process is complete for solid fractions below 30% for all cooling rates. The maximum nucleation rate significantly increases with increasing cooling rates.