Coarsening of the delta ' phase in aluminium-lithium alloys

Transmission electron microscopy has been used to measure the size of the d elta' phase, and electrical resistivity to determine lithium concentration in the matrix: during coarsening of the delta' phase. Application of the Li fshitz-Slyozov-Wagner theory of particle coarsening has enabled independent calculation of the delta' -alpha interface energy gamma and the effective diffusivity D-eff of lithium in aluminium during delta' coarsening. For an alloy containing 7.6at.% Li, gamma is found to be 0.045 J m(-2) and D-eff a t a temperature T is defined by the equation D-eff (m(2)s(-1)) = 1.5 x 10(-6) exp (-118400/RT) Increasing the lithium concentration of the alloy to 9.8 at.% had little ef fect on the activation energy of delta' coarsening but it reduced the value of the pre-exponential factor.