EFFECT OF DIFFUSIONAL RELAXATION ON THE SHAPE CHANGE OF LIQUID B2O3 PARTICLES IN A DEFORMING CU MATRIX

Diffusional relaxation around B2O3 particles which occurs concurrently with the deformation of a surrounding Cu matrix is experimentally and theoretically analysed from the shape change of the particles. The or iginally spherical B2O3 particles in the Cu matrix become a liquid at high temperatures. Although plastic deformation of the Cu matrix induc es the particle elongation, a relaxation process operates to suppress the elongation at high temperatures. This causes smaller aspect ratios of the liquid particles than those expected from applied tensile stra ins. The relaxation is caused by the diffusion of the matrix Cu atoms along the Cu-B2O3 interface under the driving force of the excess inte rface free energy. The activation energy of the interface diffusion is evaluated as 1.7 eV. The kinetics of the shape change of a liquid par ticle in a deforming matrix is formulated including the effect of the diffusional relaxation. The theoretical calculations explain the exper imental results on the temperature and particle-size dependences of th e change in the aspect ratio of the B2O3 particles.