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materials screener > Final > Flashcards

Final Flashcards

1
Q

What is the difference between welding and brazing?

A

Welding joins metals using heat to melt parts together and filler material can be used to form a joint while brazing are metals joined by melting and flowing a filler into the joint.

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2
Q

What is the difference between steel and iron?

A

Steel has carbon and sometimes other stuff in it while iron is pure.

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3
Q

What are some BCC stabilizers?

A

CrAlTiSiMoWV

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4
Q

What are some FCC stabilizers?

A

NiCoMn

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5
Q

What is the crystal structure of RPV steels, liner and zircalloy for cladding?

A

BCC, FCC and HCP

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6
Q

Name the elemental species in nuclear fuel for LWRS before irradiation and after irradiation.

A

Before: UO2
Afterwards, fuel is approximated by 5 fission groups: Dissolved in UO2, Metallic inclusions, Second Oxide Phase, Alkali Metals and Rare Gases

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7
Q

What elements are takein into accoun in “Dissolved in UO2” fission group?

A

RE + Mo + Zr

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8
Q

What elements are takein into accoun in

“Metallic inclusions” fission group?

A

Noble Metals + Mo

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9
Q

What elements are takein into accoun in “Second Oxide Phase fission group?

A

Ba + Zr as BaZrO3

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10
Q

What elements are takein into accoun in “Alkali Metals” fission group?

A

Cs as Cs2O or Cs2UO4

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11
Q

What elements are takein into accoun in “Rare Gases” fission group?

A

Xe + Kr

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12
Q

How is the energy of an ion lost to the material if E > Ec and E < Ec?

A

When E > Ec: energy lost to ionizing (electrons)

When E < Ec: energy lost to displacements in collisions

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13
Q

What is IASCC? How does it happen?

A

Irradiation Assisted Stress Corrosion Cracking. Irradiation induces depletion of chromium at GB which normally protects against corrosion, causes radiation hardening, irradiation creep, etc.

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14
Q

What is IGSCC? Why does it happen?

A

InterGranular Stress Corrosion Cracking. If excessive corrosion and cracking ocurrs at grain boundaries.

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15
Q

How would you predict if a solid solution is possible of element a and b?

A

Hume-Rothery rules

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16
Q

Why does SCC occurs?

A

Due to a combination of stresses above certain threshold and a corrosive environment

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17
Q

What are the Hume-Rother rule?

A
  1. atomic radius differ by no more than 15%
  2. crystal structure must match or be similar
  3. valence electrons must be similar
  4. must have similar electronegativity
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18
Q

What happen to the davis bessy power plant and what caused it?

A

Borated water (coolant) leaked from cracked control rod drivemechanisms above the reactor (eating more than sx inches of carbon steel RPV. Boric Acid corrosion.

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19
Q

What does SANS stand for?

A

Small Angle Neutron Scattering

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20
Q

What does EDS stand for?E

A

Energy dispersive X-ray spectroscopy

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21
Q

What does TEM stand for?

A

Transmission electron microscope

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22
Q

What does SEM stand for?

A

Scanning Electron microscope

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23
Q

What is the importance of kirkendalls findings and what did it prove?

A

Its the motion of the interface between two metals that ocurr as a consequence of a difference in diffusion rates of the metal atoms. Important sice it proved that diffusion ocurrs through vacancy movement.

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24
Q

What is a spallation source

A

High powered proton accelerator where protons are collided with a spallation target which results in neutrons.

25
Q

what are some disrable properties of a spallation target material?

A

good thermal conductivity, small thermal exp. coefficient, good-elastic properties, good ductility, moderate activation and afterheat production, resistance to corrosion.

26
Q

What graph would you use to evaluate cooling rates to form martensite

A

TTT Graph

27
Q

Why steady-state concentration of vacancies is larger than self interstitial atoms under irradiation?

A

Dislocations are biased sink for self interstitials therefore vacancies are foten left behind.

28
Q

What are the slip planes and slip directions for FCC, BCC and HCP?

A

FCC (111) <110>
BCC (110) <111>
HCP (0001) <11-20>

29
Q

Do mechanical properties of a metal change if it is cold worked and why?

A

Yes, it affects mainly the yield strength which increases with %CW, tensile strength (increases with %CW), and Ductility (decreases with %CW) since cold working increases the # of dislocations and also reduces the size of the grains therefore also increasing the barriers to dislocation movement.

30
Q

What is a stacking fault?

A

A missing plane in the normal stacking sequence of a crystal structure

31
Q

What does the E-modulus describe in a material on an atomic level?

A

It describes the resistance to separation of interatomic atoms. It describes the elasticity of the atomic bonds and is characterize by the slope of the energy-separation curve at equilibrium

32
Q

Does the E modulus depend on orientation and why?

A

It does since stress = E * strain. Stress and strain depend on factors like grain orientation.

33
Q

What other property is related to the E-modulus?

A

The thermal expansion coefficient and the melting temperature

34
Q

What occurs in a material during a martensitic phase transformation (heat treatment) and what graph shows the fatures formed during this treatment?

A

Once in austenitic phase (heated up) the steel is quenched (rapidly cooled) not allowy interstitial C atoms to diffuse therefore creating a BCT crystal structure. TTT Graph

35
Q

What 3 factors must be fulfilled that the diffusion of a substitutional atom can occur?

A
  1. Must have enough vibrational energy to move to the next spot
  2. There must be a vacancy in a neighboring lattice space
  3. It must move towards the vacancy.
36
Q

A dislocation loop is created by a migration of what type of defects? Name all type of dislocations which characterize a dislocation loop

A 
Point Defects (Vacancies and Interstitials)
Edge, Screw and Mixed
37
Q

What does schmidts law describe?

A

describes the stress along the slip plane when uniaxial force is applied in a direction not perpendicular to the slip plane

38
Q

What type of figures are used to describe texture?

A

Pole figure

39
Q

What does texture mean?

A

It means the material has preferential orientation in certain direction which means macroscopic properties will be anisotropic (they differ depending on the direction).

40
Q

How much martensite will form in 316SS using a cooling rate of 5 degrees celcius per second and why?

A

None since 316SS is austenitic.

41
Q

A liquid solidifies. How can we determine the critical radius needed to form a solid crystal? What forces are competing?

A

The volume term and the surface tension term compete. The critical radius is calculated by summing both terms.

42
Q

A fine cold worked and an annealed alloy are exposed to C rich environment at elevated temperature. Which mmaterial will carburize faster?

A

The cold worked metal because it will carburize along the grain boundaries.

43
Q

Is diffusion faster for open or close-packe crystal structures?

A

open crystal structures

44
Q

Is diffusion slower at higher temperatures or lower temperatures?

A

Higher Tm

45
Q

Is diffusion slower for larger diffusing atoms or smaller diffusing atoms?

A

Slower for larger diffusing atoms

46
Q

Is diffusion faster for higher or lower densities?

A

Faster for lower densities

47
Q

What map gives ifnormation about deformation creep?

A

Ashby Map

48
Q

What is dislocation glide

A

When stress levels are high the creep rate is given by the ease of which dislocations are impeded by obstacles

49
Q

What is dislocation climb

A

When dislocations climb due to vacancy movement.

50
Q

Where does cobe and Nabarro creep diffuse through

A

Cobe diffuses mainly on GB and Nabarro diffuses through grains.

51
Q

Name some assumptions of the Kinchin-Pease Model

A
  1. casacade created by two-body elastic collisions
  2. Energy consumed in displacing atom neglected in energy balance
  3. energy loss by electronic stopping is treated by a cutoff energy
  4. energy transfer cross section given by hard-sphere model
  5. Arrangement of atoms in the soild is randome.
52
Q

What three types of grains are formed post-irradiation of the oxide fuel?

A

Columnar and Equiaxed Grains and Intergranular porosity

53
Q

What crystal strucrture is more brittle generally? BCC or FCC and why?

A

BCC since it has more slip systems and a lack of closed-slip plane therefore affecting ductility

54
Q

What does an intrinsic stacking fault have in common with a dislocation?

A

Stacking fault always shares a border with a partial dislocaiton

55
Q

What causes extrinsic stacking fault?

A

Interstitial accumulation

56
Q

What causes intrinsic faults?

A

vacancy accumulation.

57
Q

Explain why cold work increases a materials strength?

A

Cold work introduces dislocations (dislocaiton density increases) thereefore hindering dislocation movement resulting in increased strength.

58
Q

Does carbon diffuse faster in bcc or fcc and why?

A

In BCC. FCC intesrtitials are big but they act as a trap for carbon atoms therefore requiring more energy to release them

59
Q

Name some recommendations for extending RPV lifetime at EOL?

A

Application of low leakage core, increase ECCS water temperature, inserting dummy elements, vessel annealing, decrease conservatism of NRC.

materials screener (11 decks)

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