Strain hardening

Definition

Strain hardening, also known as work hardening, is the phenomenon where a ductile material becomes stronger and harder as it is plastically deformed. This occurs because the dislocations within the material's crystal structure multiply and interact during deformation, making further movement of dislocations more difficult. As a result, the material exhibits increased yield strength and ultimate tensile strength.

5 Must Know Facts For Your Next Test

1. Strain hardening occurs mainly in metals and alloys, making them suitable for applications requiring enhanced mechanical properties after processing.
2. As the degree of strain increases, the material can become more resistant to further deformation, which is critical in manufacturing processes like rolling and forging.
3. The process of strain hardening can lead to anisotropy in materials, meaning that their properties can vary depending on the direction of the applied load.
4. Once a material has undergone strain hardening, it can often be softened again through processes such as annealing, which allows recovery and recrystallization.
5. Strain hardening is a key consideration in metal forming operations as it influences the selection of materials and processing conditions to achieve desired mechanical properties.

Review Questions

• How does strain hardening affect the mechanical properties of a material during plastic deformation?
  • Strain hardening significantly increases both yield strength and ultimate tensile strength of a material as it undergoes plastic deformation. This is due to the multiplication and interaction of dislocations within the material's crystal structure, which makes further deformation more difficult. As a result, materials become tougher and more resistant to permanent shape changes under stress.
• Discuss the relationship between dislocation behavior and strain hardening in ductile materials.
  • Dislocations play a crucial role in strain hardening as they are responsible for allowing plastic deformation. When a ductile material is deformed, dislocations multiply and interact, creating obstacles that hinder their movement. This interaction leads to an increase in strength because the material resists further deformation; thus, understanding dislocation dynamics is essential for predicting how materials will behave under strain.
• Evaluate how strain hardening can be utilized in manufacturing processes and its implications for material selection.
  • Strain hardening can be strategically employed in various manufacturing processes such as rolling, forging, and drawing to enhance the mechanical properties of metals. By selecting materials that exhibit significant strain hardening effects, manufacturers can produce components with improved strength without changing the composition. However, this also requires careful consideration of post-processing techniques like annealing to mitigate potential brittleness or unwanted anisotropy that may arise from excessive strain hardening.

Related terms

Plastic deformation: The permanent change in shape or size of a material when subjected to stress beyond its yield strength.

Dislocation: A linear defect in a crystal structure that allows for deformation by enabling atoms to slip past each other.

Yield strength: The amount of stress at which a material begins to deform plastically and will not return to its original shape.