Cu-0.75 mass%Be合金双結晶における不連続析出

抄録

The misorientation dependence of discontinuous precipitation (DP) for [001] symmetric tilt and twist boundaries in Cu-0.75 mass%Be alloy bicrystals has been systematically investigated in a temperature range from 523 to 698 K. A grain boundary migrates at a constant rate during DP under an isothermal condition, maintaining a constant interlamellar spacing. The interlamellar spacing increases with temperature. The formation and growth of DP cells at twist boundaries are suppressed, compared with those at symmetric tilt boundaries. For the two types of grain boundary, the incubation period to initiate DP and cell growth rate at a boundary show a good correlation with the energy of the boundary. The formation and growth of cells are easier at higher-energy boundaries. The grain-boundary diffusion data have been determined through the kinetic analysis of DP using several models. Although the activation energy Q_b of boundary diffusion varies with the models, the values of Q_b are smaller than the activation energy of volume diffusion of Be in Cu. For the two types of boundary, a close correlation is found between the diffusivity and the energy of boundaries. A lower-energy boundary has a lower diffusivity with a larger activation energy and a larger pre-exponential factor.