Grain boundary segregation of carbon in iron

The distribution of C¹⁴ in a series of a-phase Fe-C alloys was studied autoradiographically. Excess carbon was present near grain boundaries in specimens equilibrated at 500‡ and 600‡C; the amount of carbon near the grain boundaries was found to decrease as the equilibration temperature increased. Electron microscopy of the specimens subsequent to the autoradiography showed that no grain boundary precipitates were present. The results are compared with the theories of nonequilibrium vacancy-aided segregation and Gibbsian adsorption, and also with McLean's model of grain boundary segregation. It is shown that the technique measures directly the quantity of thermodynamic interest, the total excess solute per unit area of grain boundary. Formerly Graduate Student, Henry Krumb School of Mines, Columbia University, New York, N. Y.. This paper is based on a thesis submitted by J. M. PAPAZIAN in partial fulfillment of the requirements of the degree of Doctor of Philosophy at Columbia University.