Transmission electron microscopy was used to measure the size of the d' phase, and electrical resistometry was used to determine the Li concentration in the matrix during coarsening of this phase. Application of the Lifshitz--Slyozov-Wagner theory of particle coarsening permitted independent calculations to be made of the d'/a interface energy and of the effective diffusivity of Li in Al during d'-coarsening. In the case of an alloy which contained 7.6at%Li, the interface energy was found to be 0.045J/m2 and the diffusivity (table 1) was described by:

D (m2/s) = 1.5 x 10-6 exp[-118400/RT]

Increasing the Li content to 9.8at% had little effect upon the activation energy for δ' coarsening, but it reduced the value of the pre-exponential factor.

Coarsening of the d' Phase in Aluminium-Lithium Alloys. B.Noble, S.E.Bray: Philosophical Magazine A, 1999, 79[4], 859-72

Table 1

Effective Diffusivity in Al-Li Alloys