The diffusivities were measured by using ns laser pulses to melt thin films that had been ion-implanted with the solute. The use of the thin-film geometry eliminated convection in the melt. The time-dependent electrical conductivity and optical reflectivity of the film during melting were measured, and the diffusivity was deduced from the 1-dimensional broadening of ion-implanted solute depth profiles. The measured Cu diffusivity was found to be some 3 times faster than that of Fe (figure 4). This was consistent with Turnbull’s cluster model for liquid Al-Fe. The diffusion coefficients which were found for Fe and Cu changed very little as the peak concentration decreased with time; thus implying little or no concentration dependence. The temperature dependence of the diffusivity was studied by using heat-flow simulations to extract temperature data from the transient conductivity data. The results for Fe diffusion in liquid Al were consistent, to within experimental accuracy, with extrapolations of previous data to lower temperatures. However, the Cu diffusivities were about twice as high as might be expected on the basis of extrapolations of previous data.

N.Isono, P.M.Smith, D.Turnbull, M.J.Aziz: Metallurgical and Materials Transactions A, 1996, 27[3], 725-30