The microstructure changes in the precipitation hardening copper alloys during the thermal process after deformation are known to exhibit complex behavior due to the simultaneous progress of various phenomena such as precipitation, recovery, recrystallization, and grain growth. Understanding the mechanism is an important issue for designing the heat treatment processes.

In this study, the microstructure changes in the Cu-Co-P alloy during thermal process after a deformation was numerically simulated based on the N model coupled with the dislocation recovery model, where the interaction between dislocations and precipitation behavior was focused. As a result, the following peculiar phenomena were calculated:

The fcc-Co formation and the Co₂P precipitation on dislocations take place simultaneously in the Cu-0.32 at％Co-0.21 at％P-0.11 at％Sn alloy. The Co particles are left inside the bulk Cu matrix in the recovery process of dislocations, and then the Co particles are re-dissolved into matrix phase. The following mechanism was proposed to explain this peculiar behavior. Since the Co particles in the bulk matrix left by the dislocation recovery have high interfacial energy, they re-dissolve into the matrix phase to release this energy. Furthermore, the decrease in Co concentration in the matrix phase due to the Co₂P precipitation on the dislocation accelerates the Co particle re-dissolution.