Materials Science And Engineering Test #2

Front 1

The quantity of mass diffusing through and perpendicular to a unit cross-sectional area of material per unit time.

Back 1

Diffusion

Front 2

What quantities are materials dependent values (depends on which material you are discussing)?

Back 2

Pre-exponential coefficiant

Activation Energy for diffusion

Front 3

γ-iron (FCC) at 900°C has a larger diffusion coefficient, for the self-diffusion of iron, than α-iron (BCC) at 900°C.

Back 3

False. The atomic packing factor is greater for FCC FE meaning that there are more interstitial spaces available in the BCC FE. Therefore, motion of interstitial atoms moves more easily.

Front 4

What do we call the energy required to initiate a reaction such as diffusion?

Back 4

Activation energy.

Front 5

What do we call the diffusion mechanism wherein net atomic migration is from a lattice site to an adjacent vacancy.

Back 5

Vacancy Diffusion

Front 6

On the basis of diffusion, why are integrated circuits typically made of aluminum (compared to Au, Ag & Cu)?

Back 6

Less interconnect aluminum atoms diffuse into the silicon.

Front 7

Gold and silver form a substitutional FCC alloy. The mechanism by which silver diffuses within gold is called:

Back 7

Vacancy diffusion

Front 8

What is the driving force for diffusion?

Back 8

Concentration Gradient

Front 9

Interstitial diffusion is normally more rapid than vacancy diffusion because:

Back 9

(1) interstitial atoms, being smaller, are more mobile; (2) the probability of an empty adjacent interstitial site is greater than for a vacancy adjacent to a host atom.

Front 10

What do we call the impetus behind a reaction, such as diffusion, grain growth, or a phase transformation.

Back 10

Driving Force

Front 11

A diffusion mechanism whereby atomic motion is from interstitial site to interstitial site

Back 11

Interstitial Diffusion

Front 12

What is the term used for defining mass flow through and perpendicular to a unit cross sectional area of solid per unit time?

Back 12

Diffusion Flux

Front 13

What is the diffusion condition for which there is no net accumulation or depletion of diffusion species (where the diffusion flux is independent of time).

Back 13

Steady-state diffusion

Front 14

What is the process by which the surface carbon concentration of a ferrous alloy is increased by diffusion from the surrounding environment.

Back 14

Carburizing

Front 15

True or False: Metal A has a greater activation energy?

Back 15

True

Front 16

True or False: the activation energy for diffusion depends on temperature?

Back 16

False

Front 17

What is the ability of a material to absorb energy and plastically deform before fracturing.

Back 17

Toughness

Front 18

True or False: Elastic deformation is permanent and non-recoverable.

Back 18

False

Front 19

True or False:
Plastic deformation is non-permanent and recoverable.

Back 19

False

Front 20

True or False: At the atomic level, during elastic deformation, bonds are breaking?

Back 20

False

Front 21

True or False
Brittle metals are normally tougher than ductile ones.

Back 21

False

Front 22

Dislocation motion occurs within a crystalline material during during what type of deformation?

Back 22

Plastic

Front 23

True or False:
Poisson's ratio is defined as the ratio of the lateral and axial strains.

Back 23

True

Front 24

Hooke's law applies to which region of the stress strain curve?

Back 24

Elastic

Front 25

True or False:
Ductility is a measure of the degree to which a material will plastically deform by the time fracture occurs.

Back 25

True

Front 26

True or False:
Yield strength is the stress at the maximum on the engineering stress-strain curve.

Back 26

False

Front 27

Which hypothetical material is the stiffest?

Back 27

E

Front 28

Which hypothetical material exhibits the greatest ductility?

Back 28

B

Front 29

True or False:
Toughness is the capacity of a material to absorb energy when it is deformed elastically and then, upon loading, to have this energy recovered.

Back 29

False

Front 30

What are three factors that should be considered in designing a test to assess the mechanical characteristics of materials for

Back 30

Environmental conditions, load duration, and the nature of the applied load (tension, compressional, shear)

Front 31

What does a material that undergoes ductile fracture show?

Back 31

necking

Front 32

True or False:True stress is defined as the instantaneous applied load divided by the instantaneous cross-sectional area.

Back 32

True

Front 33

True or False:To strengthen an alloy, dislocation motion must be impeded (assuming the material has defects).

Back 33

True

Front 34

True or False:Recrystallization can happen to a metal or an alloy that has been plastically deformed and then heated.

Back 34

True

Front 35

Would you expect it to be possible for ceramic materials to experience recrystallization?

Back 35

No

Front 36

True or False:Metals such as lead and tin do not strain harden at room temperature.

Back 36

True

Front 37

For a metal or alloy that has been plastically deformed and then annealed what happens to ductility, grain size, tensile strength, and total number of grains?

Back 37

Ductility? Increase; Tensile strength? Decreases; Grain Size? Increases; Total number of grains? Decreases

Front 38

What does a slip system consist of?

Back 38

A slip system consists of a crystallographic plane, and, within that plane, a direction along which dislocation motion (or slip) occurs.

Front 39

What is the primary slip system for a BCC crystal?

Back 39

110 plane in the -111 direction

Front 40

True or False: Most metals strain harden at room temperature?

Back 40

True

Front 41

What is the Hall-Petch Equation used for?

Back 41

Used to determine Yield strength from the average grain size.

Front 42

True or False:
The critical resolved shear stress is the value of resolved shear stress at which yielding begins; it is a property of the material.

Back 42

True

Front 43

True or False:
Addition of substitutional components into a metal will weaken the metal (this is called solid-solution strengthening).

Back 43

False

Front 44

True or False:The hardness measured from an indentation that is positioned close to a preexisting indentation will be higher than if it were positioned further away.

Back 44

True

Front 45

True or False: Defects in a crystal can slow dislocation motion; this is how strain hardening weakens an alloy.

Back 45

False

Front 46

True or False:
It is possible for two screw dislocations of opposite sign to annihilate one another if their dislocation lines are parallel.

Back 46

True

Front 47

True or False:Cold working, work hardening and strain hardening all refer to the phenomena by which a ductile metal becomes harder as it is plastically deformed.

Back 47

True

Front 48

True or False:
In general, the ways to strengthen an alloy relies on increasing the ease with which slip occurs in the alloy.

Back 48

False

Front 49

Can a cold-worked metal can regain its mechanical properties through heat treatment?

Back 49

Yes

Front 50

True or False:
In general, for metals, as grain size increases the yield strength increases.

Back 50

False

Front 51

True or False:
Defects in a crystal can slow dislocation motion; this is how strain hardening strengthens an alloy.

Back 51

True

Front 52

True or False:
Edge, screw and mixed dislocations move (slip) in response to tensile stresses applied along a slip plane and in a slip direction.

Back 52

False

Front 53

Can a cold worked metal ever regain its mechanical properties?

Back 53

Yes

Front 54

Can recrystallization happen to a metal or an alloy that has been elastically deformed and then heated.

Back 54

No

Front 55

True or False: Cold working, work hardening and strain hardening all refer to the phenomena by which a ceramic becomes harder as it is plastically deformed.

Back 55

False

Front 56

True or False:
Edge, screw and mixed dislocations move (slip) in response to shear stresses applied along a slip plane and in a slip direction.

Back 56

True

Front 57

True or False:
Addition of substitutional components into a metal will strengthen the metal (this is called solid-solution strengthening).

Back 57

True

Front 58

Slip is where elastic deformation occurs within a plane.

Back 58

False

Front 59

Would you expect a crystalline ceramic material to strain harden at room temperature?

Back 59

No; because ceramics are brittle and cannot plastically deform.

Front 60

Factors that may lead to scatter in fatigue life data include:

Back 60

Variation in mean stress, specimen fabrication and surface preparation, specimen alignment and test apparatus, metallurgic variables, variation in test cycle frequency.

Front 61

The type of fracture where crack propagation is along grain boundaries is termed:

Back 61

Intergranular

Front 62

True or False:
Creep results from cyclic loading

Back 62

False

Front 63

True or False:A material’s tendency to exhibit creep decreases with increasing temperature.

Back 63

False

Front 64

The type of fracture where the crack passes through the grains, is termed:

Back 64

Transgranular

Front 65

When designing structures (that are subject to stresses) sharp corners should be avoided because they act as points of stress concentration, or "stress raises."

Back 65

True

Front 66

For metal alloys, select three metallurgical/processing techniques that enhance creep resistance:

Back 66

dispersion strengthening by using insoluble second phase, solid solution alloying, increasing the grain sized or producing a grain structure with preferred orientation.

Front 67

True or false:
A material’s tendency to exhibit creep increases with increasing temperature.

Back 67

True

Front 68

Fatigue results from cyclic loading?

Back 68

True

Front 69

The term that describes brittle crack propagation corresponding to the successive and repeated breaking of atomic bonds along specific crystallographic planes.

Back 69

Cleavage

Front 70

True or False:
Inset square edges are places that can initiate creep cracks.

Back 70

False

Front 71

Fatigue strength and fatigue life are parameters used to characterize the fatigue behavior of metals and alloys.

Back 71

True

Front 72

Some low strength steel alloys have a ductile-to-brittle transition which suggests:

Back 72

The alloy changes to a brittle behavior with decreasing temperature.

Front 73

Cup and Cone fractures are usually associated with what type of fracture?

Back 73

Ductile