Chapter 7 Flashcards

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1
Q

Resolved Shear Stress in Crystals

A

Dislocations move on slip planes in slip directions when the shear stress on that plane in that direction exceeds a critical value

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2
Q

Resolved Shear Stress equation

A

shear stress = stress * cosine(angle between direction of load and the normal to slip plane) * cosine(angle between direction of load and slip direction)

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3
Q

Solid Solution Strengthening

A

Point defects such as substitutionals and interstitials either repel dislocations or else attract and then anchor dislocations, depending on the stress fields of the dislocation and point defect

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4
Q

Solid Solution Strengthening Cases

A

1) Where the stress fields are both tensile or both compressive, there is repulsion
2) Where one stress field is tensile and the other is compressive, there is attraction and anchoring

In both cases these point deflects make motion of dislocations harder, thus requiring larger stress for plastic deformation

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5
Q

Strain Hardening

A

As plastic deformation proceeds, more and more dislocations are generated from dislocation sources.

These dislocations repel siblings on the same slip plane and also interfere with the motion of dislocations on other slip planes, thereby increasing the stress necessary for further plastic deformation

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6
Q

Annealing

Low Temperature

A

<= 0.3 Tm (Melting Temperature in absolute scale)

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7
Q

Annealing

Recrystallization
Temperature

A

Equivalent to 0.4 Tm

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8
Q

Annealing

Recrystallization
Microstructural Changes

A

Replacement of old grains with new, nearly dislocation free grains with free orientations and equiaxed shape

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9
Q

Annealing

Recrystallization
Property changes

A

Large drop in strength

Large increase in ductility and toughness

Loss of cold-work-induced anisotropy

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10
Q

Annealing

High Temperature

A

> = 0.5Tm

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11
Q

Annealing

Ordering of stages

A

Lowest temperature to highest temperature for constant time of annealing

Shortest time to longest time for constant annealing temperature

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12
Q

Annealing

Recovery Stage
Microstructural Changes

A

Slight decrease in # of dislocations

reorganization of dislocations into orderly subgrains

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13
Q

Annealing

Recovery Stage
Property Changes

A

Elimination of residual stresses

Increase in thermal and electrical conductivity

Reduction of susceptibility to corrosion

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14
Q

Annealing

Grain Growth Stage
Microstructural Changes

A

A few grains grow by cannibalizing their neighbors

Grain becomes fewer and larger

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15
Q

Annealing

Grain Growth Stage
Property Changes

A

Slight loss of both strength and ductility at low temperatures

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16
Q

Effect of annealing on Weld Heat Affect Zone

A

If a cold-worked material is welded, the region of material near a weld which is raised to annealing temperatures will incur a loss of strength

17
Q

Ways to minimize undesirable effects if Weld Heat Affect Zone

A

Minimize the amount of energy deposited in the material during welding

Make the welding process as narrow in extent and short in duration as possible