Dislocations on the same slip plane but of opposite sign can annihilate each other when they collide. Dislocations on different slip planes need to change planes before annihilation can occur. This process takes place by edge dislocation climb and screw dislocation cross slip. Cross slip can occur over a wide temperature range, however, dislocation climb depends on diffusion processes and is a high temperature effect. Dislocations of the same sign can be reorganized to form a tilt or twist boundary and leave large volumes of the crystal dislocation free. These recovery reactions are illustrated in the diagram.