ANS:D - Recrystallisation

Diffusion-controlled phenomena involve the movement or redistribution of atoms within a material, primarily driven by diffusion processes. Among the options provided:

• Dislocation climb: Dislocation climb can involve diffusion-controlled processes, particularly when dislocations move through a crystal lattice by climbing over obstacles with the assistance of diffusion of vacancies or atoms.
• Cross-slip: Cross-slip does not necessarily involve diffusion-controlled processes. It refers to the movement of dislocations from one slip plane to another, which typically occurs via mechanisms such as dislocation glide and does not rely primarily on diffusion.
• Twinning: Twinning is not typically diffusion-controlled. It involves the formation of a mirror image of a crystal lattice across a specific plane or axis, which occurs without significant atomic diffusion.
• Recrystallization: Recrystallization can be diffusion-controlled. It involves the formation of new, strain-free grains in a deformed material, often facilitated by the migration of grain boundaries and the diffusion of atoms to promote the growth of new grains.