Effect of Interstitial Atoms on a Lattice-vacancy Diffusional Process

AN investigation has been made of the mechanism of diffusion of chromium into iron–carbon systems over the temperature range 950°–1,265° C. At temperatures above 825° C, the diffusional mechanism of chromium into iron is complicated by a change in crystal structure from a body-centred cubic lattice (α-phase) to a face-centred lattice (γ-phase). At low concentrations of carbon, a lattice-vacancy diffusional mechanism has been postulated, and a moving boundary model set up to represent this condition1. The results have confirmed that at concentrations of carbon of less than 0.16 per cent only lattice-vacancy diffusion was effective. At concentrations of carbon above this, the interstitial atoms hinder diffusion.