Transmission electron microscopic investigations indicated that, at small undercoolings, Al3Li precipitates were restricted almost entirely to the strain fields of dislocations in the early stages of aging, and nucleated preferentially on edge dislocations and low-angle dislocation boundaries. A study was made of binary Al-Li alloys which had been cold rolled to 50% reduction in area. Two types of dislocation boundary (simple tilt, planar dislocation network) were characterized by 2-beam analyses. The effect of the simple tilt boundary upon the competitive growth kinetics of the precipitates was studied, and the experimental results supported theoretical predictions of the effect of the stress field of such a boundary upon solute diffusion. The precipitates nucleated on dislocation node configurations, where the reacted dislocation had a large edge component, and on the network plane, where the dilatation stress was compressive.

Z.M.Wang, G.J.Shiflet: Physica Status Solidi A, 1995, 149[1], 105-22