Kinetics of interaction of impurity interstitials with dislocations revisited

Publication date: Available online 22 October 2018Source: Progress in Materials ScienceAuthor(s): J. Svoboda, W. Ecker, V.I. Razumovskiy, G.A. Zickler, F.D. FischerAbstractInteractions of impurity interstitial atoms with dislocations may play an important role in strengthening of structural materials as well as in other phenomena like hydrogen embrittlement. Impurity interstitial atoms occupy octahedral (typical for carbon) or tetrahedral (typical for hydrogen) sites in bcc metals, both showing solely tetragonal symmetry of three types distinguished by orientation with respect to the main crystallographic (1, 2, 3) directions. Placing an atom at one of such sites one of the three types of local multiaxial eigenstrain states is provoked. This eigenstrain state interacts with the stress field of the dislocation, and the corresponding interaction term provides a mechanical part of the generalized chemical potential of the interstitial component. For a proper description of the distribution of the interstitial component in the stressed lattice three site fractions X1, X2 and X3, corresponding to the types of sites, are necessary.Interstitials like hydrogen and carbon are mobile even at room temperature and diffuse spontaneously to places with the lowest interaction energy. As the individual types of interstitial sites are interconnected by fast diffusion paths, one can assume local equilibrium among atoms occupying the three types of interstitial sites. This fact is expressed by ...
Source: Progress in Materials Science - Category: Materials Science Source Type: research