Subgrains

Subgrains are small, discrete regions within a larger crystal grain. They are essentially smaller versions of the main grain, separated by low-angle grain boundaries. These boundaries are characterized by a slight misorientation of the crystal lattice between adjacent subgrains. Subgrains typically form as a result of plastic deformation processes, where dislocations can rearrange themselves into organized arrays. During recovery annealing, these dislocation arrays can evolve into subgrain boundaries, leading to a reduction in the overall dislocation density and energy of the material. The formation of subgrains can influence the mechanical properties of a material, such as its strength and ductility. Smaller subgrain sizes generally lead to increased strength due to the Hall-Petch effect, where the grain boundaries act as barriers to dislocation motion. Subgrains can also play a role in dynamic recrystallization, a process that can occur during high-temperature deformation and lead to the formation of new, strain-free grains. The study of subgrains is important in materials science for understanding and controlling the microstructure and properties of metals and other crystalline materials.