Ostwald ripening of spherical Fe particles in Cu-Fe alloys

摘要

The coarsening of spherical γ-Fe and α-Fe precipitate particles in Cu-Fe alloys aged at 600, 650 and 700 ℃ has been studied by measuring both the particle size by transmission electron microscopy and the Fe concentration in the Cu matrix by electric resistivity. The average size of γ-Fe and α-Fe particles increases with ageing time t as t~(1/3), as predicted by the Lifshitz-Slyozov-Wagner theory. The kinetics of the depletion of supersaturation with t for γ-Fe and α-Fe particles are consistent with the predicted t~(-1/3) time law. The solubilities of Fe in equilibrium with a γ-Fe particle of infinite size are greater than those in equilibrium with an α-Fe particle of infinite size. The Fe-Cu interface energy and the diffusivity of Fe in Cu have been independently derived from the data on coarsening. The coherent γ-Fe-Cu interface energy is estimated to be 0.25 J m~(-2), and the incoherent α-Fe-Cu interface energy 0.52 J m~(-2). The pre-exponential factor and activation energy for diffusion are found to be 9.75 * 10~(-5) m~2s~(-1) and 213 kJ mol~(-1) respectively.