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  • 1 Universidad de Chile Facultad de Ciencias Físicas y Matemáticas, Departamento de Ciencia de los Materiales, Casilla 2777 Casilla Santiago-Chile
  • 2 Instituto de Ciencias de Materiales de Sevilla Américo Vespucio S/N Isla de la Cartuja Sevilla Spain
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Abstract  

The precipitation process for a concentration of CoTi of super-saturated solutions of Cu-0.50 at.% Co-0.45 at.% Ti (Cu-1 at.% CoTi) was studied through differential scanning calorimetry (DSC) and microhardness measurements. The analysis of the calorimetric curves between the environmental temperature and 900 K shows the presence of only one exothermic reaction attributed to the formation of CoTi particles in the matrix of copper. The energy of activation estimated by using the modified Kissinger method came out much lower than the corresponding to the diffusion of the cobalt and titanium in copper. We may attribute this fact to the strong contribution of the vacancies introduced by quenching. We used the formalism of Johnson-Mehl-Avrami (JMA) to assess the kinetic parameters. The energetic and kinetic evaluations and the molar heats of precipitation obtained from the isochor of van’t Hoff allow us to infer that the reaction corresponds to the formation of CoTi precipitates. The isothermal kinetics of precipitation reaction could be represented satisfactory by an overall kinetic function based in a macroscopic parameter (Vickers hardness). The kinetic parameters obtained from microhardness model are in agreements with those obtained from DSC traces.