How Cr changes the dislocation core structure of α-Fe: the role of magnetism

Cr is a critical alloying element in ferritic steels and its effect on the dislocation core structure of α-Fe is examined computationally using a quantum mechanics/molecular mechanics method. We find that Cr can significantly change the dislocation core structure of Fe where magnetism plays a crucial role. The strain-dependent magnetic interaction between Cr and the host Fe atoms is responsible for the dislocation core structure. When Cr is at the tension side of the slip plane, the Cr–Fe magnetic interaction is repulsive, which lowers the dislocation energy and pins the dislocation. When Cr occupies the compression side of the slip plane, the Cr–Fe interaction is attractive which increases the dislocation energy and promotes the dislocation to break away from Cr. (paper)