Electron microscopy
 
Precipitation of Transition Metals
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The origin of precipitate formation of transition metals is that:
         i) Transition metals increase their solubility with increasing sample temperature so that they can reach supersaturation during the cooling period,
         ii) Some transition metals, especially cobalt (Co), nickel (Ni) and copper (Cu), has sufficiently high diffusivity during the cooling period,
         iii) There exists lattice defects, nucleation sites formed by a homogeneous nucleation process, e.g. for Co, Ni and Cu, or nucleation sites formed by a heterogeneous nucleation process, e.g. for iron (Fe).

The density and size of the precipitates depend on the density of nucleation sites and on the cooling rate. Low cooling rate results in the growth of large precipitates and the shrinkage of small precipitates.

 

 

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