Ab initio based calculations revealed that Cu nanoclusters in α-Fe dramatically alter the core structure of a screw dislocation from non-polarized in pure Fe to polarized. Complementary corroborative atomistic simulations using empirical interatomic potentials revealed that the Cu nanoprecipitate substantially enhances the edge component, which was in agreement with experiment. The core path under shear stress exhibited a stable → metastable → stable transition. In contrast, Cr clusters did not change the core polarization and increased the Peierls stress, thus hardening Fe. The origin in electronic structure of the Cu lubricant effect in facilitating the shear of atomic rows and the contrasting effects of Cu and Cr was elucidated.

Lubricant Effect of Copper Nanoclusters on the Dislocation Core in α-Fe. Z.Chen, N.Kioussis, N.Ghoniem, T.Hasebe: Physical Review B, 2008, 77[1], 014103 (5pp)