Chapter 4+7 Flashcards
Cooling a moten material from liquid to solid
Solidification
Step one of the solidification process;
Nuclei of the solid phase form from the moten liquid
Nucleation
The second step in the solidification process;
Crystals grow until their boundaries meet each other-the crystals become grains
Growth
One lattice site where an atom is missing, or vacant
Point Defects: Vacancies
Extra portion of a plane or half-plane of atoms
Linear Defects: Dislocations
Grain boundaries separate grains/crystals: Polycrystalline material
Interfacial Defects: Grain Boundaries
Is how/where dislocations will move
Slip System
Dislocations’ Effects on Mechanical Properties
- dislocation movement allows materials to deform
- strain fields surround dislocations when dislocation movement
- harder to deform
What is the most densely packed planes
Slip Planes
Do vacancies exits in all materials?
Yes
Where do lattices distort within linear defects?
Around the dislocated plane
With interfacial defects: grain boundaries what are those boundary’s?
They are areas of atomic mismatch/defects
With the slip system how do crystals want to be (location wise)?
They preferred to be lying in the directions of the slip systems where slip occurs more often
What are some characteristics of different grain strengths?
- dislocation motion happens because of grain boundaries
- dislocations have to change direction at boundary interface; this becomes more difficult as the crystallographic disorientation increases dislocations(stronger!)
Smaller Grain Size means what?
That there is more grains = more grain boundaries = blocks more dislocations (stronger)
