The Kinetics of the Precipitation of Co from Supersaturated Cu-Co Alloy

Abstract

The kinetics of the precipitation of Co from a supersaturated solid solution of Cu-0.95 at. pct Co was investigated by isochronal annealing applying differential scanning calorimetry (DSC) with heating rates in the range 5 to 20 K min -1 . The corresponding microstructural evolution was investigated by high-resolution transmission electron microscopy (HRTEM) in combination with electron energy loss spectroscopy (EELS). Upon isochronal annealing, spherical Co precipitates of fcc crystal structure form. Kinetic analysis by fitting of a modular phase transformation model to, simultaneously, all DSC curves of variable heating rate measured for Cu-0.95 at. pct Co showed that the precipitation-process mechanism can be described within the framework of this general phase transformation model by continuous nucleation and diffusioncontrolled growth. By introducing additional microstructural information (here, the precipitateparticle density), for the first time, values for the separate activation energies of nucleation and growth could be deduced from the transformation kinetics.

TaC Precipitation Kinetics During Cooling of Co−Re‐Based Alloys

“…The KWN model, which has been widely adopted as a precipitation modeling framework at constant temperature accounting for concurrent nucleation, growth, and coarsening kinetics, was adapted to isochronal cooling (see Supporting Information and refs. [5,34]). Particle coarsening was neglected in this contribution.…”

“…[31,32] It was recently extended to isochronal cooling processes. [33,34] In the frame of this work, the in situ measurements of precipitate solubility in the matrix and volume fraction of nanosized precipitates were used as constraints to the model. The details can be found in the Supporting Information, [5] a summary follows here.…”