An Al-3.7wt%Cu alloy was subjected to aging treatments at between 453 and 548K. The diffusion coefficients of Cu in the alloy were then determined from Cu concentration profiles measured across the grain boundary. A high spatial resolution analytical electron microscope, capable of forming a 1nm probe, was used to measure the concentration profiles. As the aging temperature was lowered, the diffusion coefficients tended to deviate from the values extrapolated from higher annealing temperatures (figure 1). It was suggested that this deviation was due to the presence of quenched-in excess vacancies.

The concentration profiles were also measured for boundaries having various misorientation angles. It was shown that the concentration profiles were essentially the same, regardless of the misorientation angles and of the boundary characteristics; except for misorientation angles of less than a few degrees.

Diffusion Analysis across Grain Boundary in Al-3.7mass%Cu Alloy Using Analytical Electron Microscopy. T.Fujita, K.Kaneko, Z.Horita: Materials Transactions, 2003, 44[7], 1336-42

Figure 1

Diffusivity of Cu in Al-3.7wt%Cu

(Line indicates results extrapolated from higher temperatures)