MAT2210 - Eric - Lecture 1-3

The dislocation can move by requiring [blank_start]........ bond[blank_end] to be broken at a time.

Positive and negative dislocations move in opposite directions to produce shear of the [blank_start]same[blank_end] sign.

Positive and negative dislocations (of same type, e.g., screw) attract each other, positives (or negatives) repel.

The slip plane is defined as ......

For an edge dislocation, the slip plane is defined as the plane which contains both the line direction an Burgers vector of the dislocation.

Dislocation motion can be conservative or non-conservative: • Conservative motion [blank_start]involves no mass transport[blank_end] (i.e., diffusion) • Non-conservative motion requires [blank_start]the addition/subtraction of atoms[blank_end] or [blank_start]vacancies to the extra half[blank_end] plane

The force required to move the dislocation is known as .......?

Enter the symbols the Frank's rule formula (not given in the formula sheet by the way): T = [blank_start]..............[blank_end] Use * as a multiplication sign , alpha as a constant alpha, G as a shear modulus and b as a Burgers vector.

The Peierls stress is the stress to glide a dislocation through an otherwise perfect crystal.

What is the definition of the dislocation width?

Why is the energy or stress is minimised by slip on the close packed planes in the close packed directions?

Which type of dislocations is more mobile and hence has smaller Pierls Stress?

The energy or stress increases with a decrease in dislocation width.

In FCC metals, Peierls stress is a strong function of temperature while in BCC metals, Peierls is not a strong function of temperature.

What can cause an increase in number of dislocations/ dislocation density? Choose one or more than one of the answers.