THE INTERFACE STRUCTURE OF THE BETA-PRECIPITATES IN NI-12 AT-PERCENT BE ALLOY

The atomic structure of the interphase boundaries between superfine plate-shaped beta-precipitates with B2 structure and the alpha-matrix with f.c.c. structure in a Ni-12 at% Be alloy is investigated by HREM and supported atom probe microanalysis. It is found that the broad interfaces of the beta-plates are semicoherent with an array of misfit dislocations, whereas the rims of the beta-plates are coherent with the matrix, although the misfit is a high as 29%. The coherency of the rims was attributed to the lack of nearly pre-existing dislocations which might contribute to the generation of misfit dislocations, as the thickness of the beta-plates is too small.