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Chapter 5
MSE 2001
23
Other
Undergraduate 4
04/24/2016

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Term
Edge dislocation line moves ___ to applied stress.

Screw dislocation line moves ___ to applied stress.
Definition
Parallel

Perpendicular
Term
Geometric slip plane
Definition
The plane of the dislocation
Term
Crystallographic slip plane
Definition
The highest atomic density plane
Term
Burgers vector connects...
Definition
The atoms of closest approach
Term
What 2 assumptions must Burger's Vector meet in order to be chosen?
Definition
1. Connects lattice points (equivalent lattice positions)
2. Shortest vector
Term
Twin boundaries
Definition
Reflections across a mirror plane to generate the structure
Term
Decreasing the grain size, _____ the strength.
Definition
Increases
Term
In edge dislocation, Burgers vector is _____ to dislocation line.

In screw dislocation, Burgers vetor is _____ to dislocation line.
Definition
Perpendicular

Parallel
Term
Impeding the motion of dislocations, _____ the strength
Definition
Increases
Term
Dislocations allow plastic deformation to occur at ____ stresses than if they were not present
Definition
Lower
Term
4 ways to impede motion of dislocations / increase strength
Definition
1. Addition of impurities / solute / alloying
2. Increase dislocation density / strain hardening
3. Decrease grain size / grain refinement decrease
4. Presence of volume / precipitation / precipitation hardening
Term
Climb
Definition
The motion of an edge dislocation that occurs when vacancies migrate to the extra half plane of atoms
Term
The probability of a dislocation climb _____ as temperature increases.
Definition
Increases
Term
Are dislocations thermodynamic defects?
Definition
NO
Term
Is a vacancy a thermodynamic defect?
Definition
YES
Term
Edge dislocation
Definition
A dislocation that is formed by the insertion of an extra half plane into an otherwise perfect region of a crystal.
Term
Why is there a tension and compressive side of a dislocation?
Definition
Because where the dislocation is inserted, the side with the fewer amount of atoms has tension to spread its area further out. Then the side with more atoms, tries to compress its area to fit the smaller side.
Term
Why do edge dislocations tend to form symmetric tilt boundaries?
Definition
Because the edge dislocations act as a wedge that tilts the two halves of the grain about an axis that lies in the plane of the boundary.
Term
The energy of a dislocation is proportional to ______.
Definition
Square of Burgers Vector
Term
Simply, how do you strengthen a metal?
Definition
By impeding the dislocation motion.
Term
How does plastic deformation occur, with regards to dislocation?
Definition
By dislocation motion
Term
To make material more ductile, do you add or remove dislocation lines?
Definition
Add
Term
Why is FCC more ductile than HCP?
Definition
Because it has more slip systems and nonparallel slip planes (this means that it is easier to pull apart, bc they're not parallel)
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