GROWTH OF DELTA ON DISLOCATIONS IN A DILUTE AL-LI ALLOY

The quantitative results of delta' growth kinetics on dislocations in an Al-2.27 wt pet Li alloy demonstrate that at temperatures greater th an 0.5 of the homologous melting temperature, T-m, volume diffusion is the dominant mechanism. However, a small contribution, approximately one atom in 300, is made by pipe diffusion through the dislocation. Th is can be established by careful examination of dislocation climb asso ciated with precipitate growth. An analysis based on the S' growth kin etics and diffusion equation gives an activation energy of 0.56 eV for Li pipe diffusion. At temperatures <0.5 T-m, delta' precipitate growt h is faster when associated with dislocations, and here, pipe diffusio n is necessary to account for the kinetics observed.