2005 年 45 巻 9 号 p. 1335-1344
A numerical model was developed to simulate the competing precipitation of Cu particles on dislocations and in the matrix in Fe-Cu alloys. The nucleation and growth rates and the remaining Cu concentration in the matrix were calculated successively at a large number of fine discrete time steps. In the absence of dislocations the results for precipitation in the matrix that was assumed to occur homogeneously were in essential agreement with those of Langer-Schwartz (L-S) model and Lifshitz-Slyozov-Wagner (LSW) coarsening theory. The heterogeneous precipitation on dislocations was incorporated taking into account the development of solute-depleted zone around dislocations. The coarsening behavior of particles on dislocations and in the matrix deviated substantially from those of previous theories probably due to the interaction of diffusion fields between heterogeneous and homogeneous precipitation zones. In other words, coarsening can occur at the expense of smaller particles nucleated in the matrix at later stages. The bcc to fcc transformation of Cu particles that occurs during growth was likely to accelerate the coarsening of Cu particles. The simulation results agreed well with experiment in respect of the particle number and mean particle radius, but the model yielded a considerably narrower particle size distribution than experiment reported in the literature.
