Peculiarities of the diffusion of carbon in iron

Abstract

1. Diffusion of carbon inα andγ-irons is non-uniform: at 550 to 950°C, carbon enriches preferentially the grain boundaries; the diffusivity of carbon along grain boundaries of ferrite is three to four higher than inside the grain. An enrichment with carbon of theα-solid solution is also observed in regions adjoining the grain boundaries. 2. The diffusion rate and the distribution of carbon within a single grain are changed by alloying. Addition of substantial amounts of certain elements curtailing theγ loop considerably increases the penetration depth of carbon on account of boundary diffusion developing inγ-iron. The concentration gradient of carbon between boundary and interior of a grain is less in alloyed than in unalloyed iron.