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The misorientation dependence of discontinuous precipitation (DP) at [001] twist boundaries in Cu-0.75 wt pct Be alloy bicrystals has been systematically investigated in the temperature range 523 to 723 K. A good correlation is found between both the incubation period, , to initiate DP and cell growth rate, v, and the energy of boundaries. The maximum of and the minimum of v occur where the cusps of the boundary energy exist. The formation and growth of DP are easier at higher-energy boundaries. The DP cells at [001] twist boundaries nucleate and grow less than those at [001] symmetric tilt boundaries in the same-alloy bicrystals. A kinetic analysis of DP using the models of Turnbull and Petermann and Hornbogen has yielded grain-boundary diffusion data. Although the activation energy, Q b , of boundary diffusion changes with the models, the values of Q b are smaller than the activation energy for volume diffusion of Be in Cu. The diffusivity in a boundary shows a close correlation with the energy of the boundary. A lower-energy boundary has a lower diffusivity with a larger activation energy and a larger pre-exponential factor.

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The effects of additions of Ag, Cr, Sb and P on the formation and growth of discontinuous precipitation (DP) reaction have been examined for different [001] symmetric tilt boundaries in a temperature range from 623 to 698 K using Cu 0.75 massBe alloy bicrystals. As the concentration of each element increases, the incubation period to initiate DP for a boundary increases, the cell growth rate for the boundary decreases, and both reach constant values. A detailed kinetic analysis of DP using the models by Turnbull and Petermann Hornbogen has enabled to determine the grain boundary diffusivity. At the stage in which the cell growth rate becomes a constant value, the activation energies Q b for boundary diffusion are in agreement with those Q v for bulk diffusion of the elements in Cu. For boundaries which have values of Q b lager than Q v before adding P, the boundary diffusivity is not affected by the P addition.