Deformation and Strengthening Flashcards
Describe an edge dislocation
A 1D (line) defect in a material. They are the equivalent of shoving an extra half-plane of atoms into a perfect crystal, and can be created by deformation.
What is the Burgers vector?
An atomic-width sized vector pointing in the direction in which a dislocation can move.
What is glide?
When a dislocation moves in the direction of the Burgers vector.
What is climb?
When a dislocation moves in a direction normal to the Burgers vector.
What is dislocation sign?
A symbol that looks like a T, with the long leg pointing in the direction of the extra half-plane of atoms.
How does sign affect dislocation mobility?
Same-sign dislocations repel, like-sign dislocations annihilate.
How are dislocations created?
By deformation.
Describe the principle of work hardening
Deforming a material increases the dislocation density within it. Dislocations impede one another’s movement because their strain fields may be repulsive. Deformation depends on dislocation movement, therefore impaired dislocation movement lends to a higher strength.
Describe plastic deformation
The shear movement of atomic planes across one another, resulting in permanent deformation.
What is solute strengthening?
Dissolving small amounts of one metal in another to reduce dislocation mobility by introducing foreign strain fields that repel dislocations.
What is a substitutional solute atom?
One which becomes part of the host material’s atomic lattice.
What is an interstitital solute atom?
One which sits in the gaps between the host atoms.
Describe dispersion strengthening.
The addition of small particles to a material so as to impede dislocation movement. Closely spaced particles are most effective at limiting movement.
