3662.     WERT, C. A.  Precipitation From Solid Solutions of Carbon and Nitrogen in Alpha-Iron.  Jour. Appl. Phys., vol. 20, 1949, pp. 943-949; Chem. Abs., vol. 44, 1950, p. 508.

        Formation of precipitates from the solid solutions of C and N in a-Fe was studied by means of the internal friction peak associated with the stress-induced interstitial diffusion of the solute atoms.  A transformation law fits the experimental data.  The data show the following:  91) Fe₃C precipitates in the shape of spheres; (2) an intermediate phase in the precipitation of N forms in the shape of disks; and (3) within the experimental error no continuous nucleation is indicated.  From the results of a derivation made by Zener, the mean distance between nuclei is calculated for Fe₃C.  For C concentrations of about 0.016 wt. %, this distance is about 800, 2,000, and 7,000 Å. At 27°, 102°, and 312°, respectively.  With appropriate experimental conditions, the temperature dependence of the precipitation rate is about the same as the temperature dependence of the diffusion rate of the solute atoms.