Extrinsic obstacles and loop formation in deformed metals and alloys

Abstract

The mechanisms leading to the formation of various types of loops and dipoles by moving dislocations have been investigated in several metals and alloys. Dissociation loops in TiAl and Ti₃Al are nucleated by similar processes, involving either glide or climb dissociation mechanisms. Cross-slip loops in TiAl, Ti, and Fe are the result of the collision of kinks gliding in different planes along screw dislocations (cross-kink mechanism). The role of extrinsic small-size obstacles in the initiation of these mechanisms is discussed. New experiments in Ti and Fe containing various amounts of solute elements show that extrinsic obstacles strongly enhance the rate of loop production by the cross-kink mechanism.

Keywords:

• dislocation motion
• deformation
• metal
• alloy
• dissociation loop
• cross-slip loop