Precipitation and dissolution of Co granules in CuCo alloys: Reverse effects of Joule heating

Measurements of resistance R versus electrical current I were performed during annealing of melt-spun pure Cu and Cu90Co10 ribbons using linearly varying current Joule heating. Typical results of Cu90Co10 samples show three characteristic stages. For low applied currents (I<4.0 A), a metallic behavior is observed and compared with pure Cu samples. Precipitation is the dominant process for intermediate currents (5.0 A<I<9.0 A). Re-solution of precipitated Co back to Cu matrix appears for high current values (I>9.0 A). Competition between precipitation and dissolution of Co granules depends also on the cooling rates, and we observed that it is possible to freeze high temperature off-equilibrium configurations down to room temperature after an appropriate quenching. Experimental annealing conditions were simulated using the Monte Carlo–Metropolis method, with Kawasaki dynamics of diffusing atoms, to study the kinetics of transformations in the Cu–Co system. Simulations show that precipitation and re-solution competition occurs as functions of both temperature and time. A relationship between simulated Co atoms configuration and resistance measurements is made