ch 8 - deformation and strengthing

Question 1

fundamental mechanism of plastic deformation

Answer 1

The distortion and reformation of atomic bonds

Question 2

plastic deformation corresponds to

Answer 2

the motion of large numbers of dislocations

Question 3

How plastic deformation occurs in metals?

Answer 3

By slip (edge dislocation)

Question 4

the process by which plastic deformation is produced by dislocation motion

Answer 4

slip

Question 5

the plane on which the motion occurs

Answer 5

slip plane

Question 6

the direction within that plane on which the motion occurs

Answer 6

slip direction

Question 7

How many slip systems in FCC

Answer 7

12 identical slip systems

Question 8

The amount of slip systems explains what phenomena?

Answer 8

the more slip systems explains ductile materials while less explains brittle material

Question 9

What leads to resolved shear stress?

Answer 9

a tensile stress applied to a crystal will have tensile and shear components unless it is aligned parallel or perp to a slip system. (Incline plane)

Question 10

What condition must be met for dislocation motion?

Answer 10

Tr>Tcrss

Question 11

ordinarily ductility is sacrificed when an alloy is strengthened (T or F)

Answer 11

true

Question 12

What defines a materials strength properities?

Answer 12

Restricting or Hindering dislocation motion

Question 13

(T or F) Grain Boundaries are barriers to slip

Answer 13

True

Question 14

How does grain size reduction increase strength?

Answer 14

Smaller grain sizes = more barriers to slip, Barrier strength increases with increasing angle of misorientation

Question 15

(T or F) a fine grained material is harder and stronger than a coarse-grained material

Answer 15

True

Question 16

Does grain size reduction improve toughness for many alloys?

Answer 16

Yes

Question 17

Where do small impurities tend to concentrate dislocations>

Answer 17

Compressive Side

Question 18

Where do large impurities concentrate at dislocations?

Answer 18

Tensile Side

Question 19

The formation of extremely small dispersed particles of a second phase within the original phase matrix

Answer 19

Precipitation Strengthening

Question 20

Implementing impurity atoms to increase the strength of a material

Answer 20

Solid Solution Strengthening

Question 21

How to accomplish precipitation strengthening

Answer 21

Appropriate heat treatment

Question 22

the phenomenon by which ductile metal becomes harder and stronger as it is plastically deformed; defined as deformation at temperatures well below the melting point

Answer 22

Strain hardening (Cold working)

Question 23

4 types for strain hardening

Answer 23

forging, rolling, drawing, and extrusion

Question 24

As dislocation density increases, so does

Answer 24

yield stress

Question 25

As cold work is increased, it impacts

Answer 25

1. ) Yield Stress increases
2. ) Tensile Stress increases
3. ) Ductility decreases

Question 26

During cold working, the cross section area tends to

Answer 26

decreases

Question 27

4 ways to increase strength in metals (aka reduce motion to dislocations)

Answer 27

1. ) Decrease Grain Size
2. ) solid solution
3. ) Precipitate hardening
4. ) Cold working

Question 28

3 processes of heat treatment in cold working

Answer 28

1. ) recovery
2. ) re crystallization
3. ) Grain growth

Question 29

the relief of some of the internal strain energy of a previously cold-worked metal usually by heat treatment

Answer 29

recovery

Question 30

The formation of a new set of strain-free grains within a previously cold-worked material

Answer 30

recrystallization

Question 31

The driving force for recrystalization

Answer 31

the difference in internal energy between strained and unstrained material

Question 32

During recrystallization, what properties are restored

Answer 32

Softer and becomes more ductile

Question 33

(T or F) Recrystallization temperature decreases with increasing %CW

Answer 33

True

Question 34

(T or F) Recrystallization temperature increases with increasing purity

Answer 34

False (Tr decreases with increasing Purity)

Question 35

temperature at which recrystallization just reaches completion in 1 hour

Answer 35

Recrystallization temperature

Question 36

At longer times, average grain size increases during cold working

Answer 36

Grain growth

Question 37

Recovery ideal heating

Answer 37

0.3Tm

Question 38

Recrystallization and grain growth heating

Answer 38

0.6-0.7Tm

Question 39

How does plastic deformation occur in polymers?

Answer 39

Breaking of the secondary bonding between chains in the crystalline regions of the polymer

Question 40

How do brittle polymers break?

Answer 40

The polymer backbone extends in length beyond a certain point