Solute Trapping of Ge in Al

Abstract

Partitioning during rapid solidification of dilute Al-Ge alloys has been investigated. Implanted thin films of Al have been pulsed-laser melted to obtain solidification at velocities in the range of 0.01 m/s to 3.3 m/s, as measured by the transient conductance technique. Previous and subsequent Rutherford Backscattering depth profiling of the Ge solute in the Al alloys has been used to determine the nonequilibrium partition coefficient <i>k</i>. A significant degree of lateral film growth during solidification confines determination of <i>k</i> to the placing of an upper bound of 0.22 on <i>k</k> for solidification velocities in this range. We place a lower limit of 10 m/s on the "diffusive velocity," which locates the transition from solute paritioning to solute trapping in the Continuous Growth Model.