Precipitate size distribution in alloys with and without lattice misfit

Via three-dimensional atomistic computer simulations, the influence of a la ttice misfit between precipitates and matrix on the precipitate size distri bution has been investigated during phase separation in a binary alloy. The elastic interactions are modeled by springs connecting nearest neighbor at oms. The difference in size between the two species of atoms, specified by the misfit parameter , leads to effective long range interactions. Perfonni ng simulations with five different values of delta we find a broadening of the scaled precipitate size distribution for delta > 0.5% in comparison wit h the case of no misfit. Additionally, the size of the largest precipitate in the system increases with increasing misfit. We also observe a percolate d network-like precipitate structure for a concentration of solute atoms as low as 20 at % at large misfit. We interpret these effects as due to an in creased tendency of the precipitates to coalesce, which is caused by their nonspherical shape, their alignment along the [100] directions and their re gular arrangement.