Lecture 9 Flashcards
Assuming an extra half plane does not extend to the free surfaces at a and b…
- form dislocation segment a
- form dislocation segment b
- eventually forms a closed dislocation loop
What is a dislocation?
the boundary between a slipped and unslipped area
When must a slipped area must have a closed boundary (dislocation loop)?
If the slipped area does not touch the surface (or grain boundaries)
What are the ways a dislocation can end?
- extend to a surface
- connect with another dislocation
- form a closed loop
What is cross slip?
Mechanism that allows screw dislocations to change slip planes in FFC metals
Which type of dislocation can cross slip happen in and why only that one?
Only screw because they do not have a fixed slip plane
When would a screw portion change the slip plane?
If the loop expansion encounters an obstacle or another {111} plane has a larger resolved shear stress
When does a dislocation loop expand?
Under applied shear stress
When does double cross slip occur?
When the loop changes glide/slip plane again.
What condition must be true for a screw dislocation to move from one glide plane to another?
They contain the same Burgers vector
