Low-angle grain boundary

Definition

A low-angle grain boundary is a type of defect in crystalline materials characterized by a misorientation of less than 15 degrees between adjacent grains. These boundaries are formed by the alignment of dislocations, which helps to accommodate the small angle of misorientation and can influence the material's mechanical properties.

5 Must Know Facts For Your Next Test

1. Low-angle grain boundaries typically have a lower energy compared to high-angle grain boundaries, making them more stable under certain conditions.
2. These boundaries often consist of an array of dislocations that accommodate the small angle of misorientation, which can contribute to the overall plasticity of the material.
3. In materials science, low-angle grain boundaries can serve as barriers to dislocation movement, influencing the yield strength and hardness of metals.
4. The presence of low-angle grain boundaries can be critical during processes such as recrystallization and grain growth, as they affect how grains evolve in microstructures.
5. Characterizing low-angle grain boundaries is essential in understanding the mechanical behavior of polycrystalline materials, particularly in relation to their strength and ductility.

Review Questions

• How do low-angle grain boundaries influence the mechanical properties of materials?
  • Low-angle grain boundaries influence mechanical properties by serving as barriers to dislocation motion, which increases yield strength and hardness. They help in accommodating strain within the crystal structure due to their arrangement of dislocations. This can enhance plasticity in materials under stress, allowing them to deform without fracturing.
• Discuss the role of low-angle grain boundaries during recrystallization and grain growth processes.
  • During recrystallization, low-angle grain boundaries can facilitate the movement and rearrangement of grains, leading to a refined microstructure. As grains grow, low-angle boundaries may help maintain stability by reducing energy levels associated with larger misorientations. Their presence affects how quickly and effectively grains can transform, which is crucial for optimizing material properties.
• Evaluate the impact of low-angle versus high-angle grain boundaries on the overall stability and performance of polycrystalline materials.
  • Low-angle grain boundaries contribute to enhanced stability and performance by providing lower energy states and facilitating dislocation movements within materials. In contrast, high-angle grain boundaries often lead to increased energy levels and can act as more significant obstacles to dislocation motion. This difference affects overall mechanical behavior, where materials with a higher proportion of low-angle boundaries may demonstrate improved ductility and toughness compared to those dominated by high-angle boundaries.

Related terms

dislocation: A line defect in a crystal lattice where atoms are misaligned, significantly affecting the mechanical properties of materials.

high-angle grain boundary: A grain boundary with a misorientation greater than 15 degrees, generally resulting in higher energy and different properties compared to low-angle boundaries.

grain size: The average diameter of grains in a crystalline material, which can impact strength, ductility, and other mechanical characteristics.