Shape evolution of fcc Co–Fe precipitate particles during coarsening in a Cu matrix

Abstract

The shape evolution of fcc Co–Fe precipitate particles during coarsening in Cu-1.37 at.% Co-0.83 at.% Fe alloy single crystals has been examined by the transmission electron microscopy observation. Co–Fe particles change from sphere to cuboid and eventually flatten into a plate-like one with increasing particle size. The size-dependent equilibrium shapes of Co–Fe particles were discussed by considering the elastic strain energy of particles together with the interface energy between the particles and the matrix. To evaluate the elastic strain energy, elastically homogeneous but anisotropic particles with purely dilatational misfit strains are taken into account. The experimentally observed shape transition can be satisfactorily explained by the simple energy analysis.