Chapter 4

Question 1

Ideal strength of a Material

Answer 1

Possible to approach this in microscopic fibers

Strength of macroscopic chunks of materials limited by crystal defects

Question 2

0 D

Vacancy

Answer 2

Missing atom where one should exist in lattice

Question 3

0 D

Interstitial

Answer 3

Extra atom at location in crystal where there should not be an atom

Almost always a very small atom

Question 4

0 D

Substitutional Impurity

Answer 4

Atom of a different variety replace a native atom in the crystal

Can be larger or smaller

Question 5

1 D

Edge Dislocation

Answer 5

Linear defect in crystal where the Burgers vector is perpendicular to the line of the dislocation

Characterized by the insertion of an extra half-plane into the crystal

Question 6

1 D

Screw Dislocation

Answer 6

Linear defect in crystal where the Burgers vector is parallel to the line of the dislocation

Characterized by a spiral pattern of atoms about the dislocation

Question 7

2 D

Grain Boundaries

Answer 7

Location where two crystals of different orientation meet.

Question 8

2 D

Phase Boundary

Answer 8

Surface between two different materials

Question 9

2 D
(Of secondary importance)

Answer 9

Twin boundaries -

Stacking Faults -

Question 10

3 D

Volume Defects

Answer 10

Voids

Cracks

Particles of a different material

Question 11

Plastic Deformation in Metallic Materials at Low Temperatures is due to line defects

Answer 11

Both edge and screw dislocations produce permanent shear strain in response to applied shear stress of sufficient magnitude

Caused by slip in planes of maximum area packing density in direction of maximum linear density

At low temperature, motion of dislocations can be impeded by point, line, plane, and volume

At high temp, only point and volume defects are effective for strengthening