crossslip

Cross-slip, sometimes written crossslip in older literature, is a dislocation mechanism in crystalline materials by which a screw dislocation moves from its original glide plane to a different, intersecting glide plane. This allows the dislocation to continue plastic deformation when its primary glide plane becomes blocked by obstacles or requires switching slip systems under changing stress.

In a crystal with multiple close-packed planes—especially face-centered cubic metals such as copper, aluminum, nickel and many alloys—screw dislocations can cross-slip between {111} glide planes along directions common to those planes. The process is thermally activated and proceeds via the formation of jogs on the dislocation line, or via double-kink nucleation, enabling the segment of the dislocation to glide on a new plane. The energy barrier for cross-slip is higher than for motion within a glide plane, so cross-slip rates rise with temperature and applied resolved shear stress.

Cross-slip is a key contributor to work hardening and the strain-hardening behavior of metals, as it allows dislocations to switch planes and interact more readily, increasing the dislocation density and entanglement. It is more readily observed in FCC metals at moderate to high temperatures; in BCC metals, cross-slip is possible but frequently limited by higher Peierls barriers, so other mechanisms like climb or cross-slip on different planes may dominate.

In summary, cross-slip is the mechanism by which screw dislocations alter glide planes, enabling continued plastic flow and influencing mechanical properties through dislocation interactions and work hardening.