8. Dislocations Flashcards
What are the two kinds of point defects that can occur?
- vacancies (missing atoms in crystal structure)
2. Interstitial deffects (extra atom in crystal structure)
As the temperature increases the number of vacancies in a crystal at equilibrium _____ (decreases/increases)
increases
How does plastic deformation occur in a crystalline solid?
By the propagation/movement of dislocations known as SLIP
Define dislocation
linear crystalline defects whose motion gives rise to plastic deformation in crystalline materials
define slip
the process by which plastic deformation is produced by dislocation movement
What causes slip?
the application of shear stress
During slip, what happens to the bonds holding the plane together?
they are severed and reformed
Define slip plane
the plane along which dislocations move
Define slip system
describes the preferred slip plane and slip direction for dislocation movement
What determines the slip system?
the crystal structure
the slip system is such that the ____ ____ is minimized with dislocation movement
atomic distortion
Is there only one slip system per crystal structure?
no, many can exist
Slip occurs
a. along the plane with the ____ _____ _____ (slip plane)
b. along the direction with the _____ _____ ____ (slip direction)
a. densest atomic packing
b. highest linear density
define resolved shear stresses
the components of the shear stress which act along the tensile axis
If multiple slip systems exist, the one with the ____ (minimum/maximum) resolved shear stress is preferable
maximum
