Lubricant effect of copper nanoclusters on the dislocation core in α-Fe

Ab initio based calculations reveal that Cu nanoclusters in α-Fe dramatically alter the core structure of a screw dislocation from nonpolarized in pure Fe to polarized. Complementary corroborative atomistic simulations using empirical interatomic potentials reveal that the Cu nanoprecipitate substantially enhances the edge component, which is in agreement with experiment. The core path under shear stress exhibits a stable→metastable→stable transition. In contrast, Cr clusters do not change the core polarization and increase 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 is elucidated.