A model describing the microstructure evolution in Fe–Cu alloys during thermal aging

A numerical model treating the full course of precipitation as a concomitant process has been presented to calculate directly the time evolution of the precipitate size distribution during aging of Fe–Cu alloys. The model was first validated by comparing with the reported experimental results and then used to investigate the microstructure evolution during aging of a Fe–1.34 at.%Cu alloy in details. It has been demonstrated that the heating process only affects the nucleation period. After the beginning of the bcc → 9R transformation, the microstructure evolution can be divided into three stages: bcc → 9R transformation, no transformation and 9R → bcc transformation. In the late stage of aging, almost all particles are of 9R structure. The mean particle radius varies linearly with the cube root of time and the particle number density varies linearly with the reciprocal of time.