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Materials Exam Upload > Metals and Ceramics > Flashcards

Metals and Ceramics Flashcards

1
Q

What is a crystalline and amorphous/non-crystalline material?

A

Crystalline:
A material whose molecules are arranged in a highly ordered structure.

Non-crystalline:
A lack of systematic and regular arrangement of molecules.

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2
Q

What are the three common lattice structure?

A
  • Body Centered Cubic (BCC)
  • Face Centered Cubic (FCC)
  • Hexagonal Closed Packed (HCP)
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3
Q

What are some properties of ceramic crystal structures? (2)

A
  • Composed of atleast two elements
  • Electrically charged ions instead of atoms
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4
Q

What influences the crystal structure in ceramic crystals? (2)

A
  • Charge of ions
  • Relative size of cations and anions
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5
Q

What are the kinds of lattice defects? (4)

A
  • 0-dimentional
  • 1-dimensional
  • 2-dimensional
  • 3-dimensional
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6
Q

What are the 0-dimensional defects?

A

Point defects

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7
Q

What are the 1-dimensional defects?

A

linear defects, dislocations

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8
Q

What are the 2-dimensional defects?

A

Interfacial defects, stacking faults, grain boundaries

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9
Q

What are the 3-dimensional defects?

A

Precipitates, Impurities, Voids

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10
Q

What are some examples of a point defect?

A

Atom from crystal / foreign atom in interstitial site (Interstitial / self-interstitial atom)

Foreign atom in lattice structure (substitutional atom)

Unoccupied lattice site (vacancies)

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11
Q

Explain some 1-dimensional defects (2)

A

Edge dislocation: A line around which some atoms are misaligned

Screw dislocation: Topological defect formed by distortion due to sheer stress.

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12
Q

What is a process that increases the number of dislocations in a material?

A

Cold forming.

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13
Q

What are Interfacial / 2-Dimensional defects?

A

Regions of the material with different crystal structure or orientation.

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14
Q

What are some benefits of grain boundaries? (2)

A
  • Block Migration of dislocations
  • Give the material better strength behavior
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15
Q

What are bulk / 3-dimensional defects? Gives examples (3)

A

They are macroscopic defects. Like pores, cracks and inclusions.

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16
Q

What is slip?

A

The process by which plastic dislocation is produced by dislocation motion.

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17
Q

What is the slip plane?

A

The crystallographic plane along which the dislocation line traverses

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18
Q

What is a slip plane?

A

It is the combination of a slip plane and a slip direction

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19
Q

What is the formula for finding the number of slip systems?

A

Slip plane x Slip direction

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20
Q

What is the number of slip planes and slip directions in BCC?

A

6, 2

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21
Q

What is the number of slip planes and slip directions in FCC?

A

4, 3

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22
Q

What is the number of slip planes and slip directions in HCP?

A

1, 3

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23
Q

What are the two properties strengthening mechanisms aim to improve?

A

Yield point and Tensile strength

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24
Q

What are the strengthening methods? (3)

A
  • Solid Solution Strengthening
  • Strengthening by Grain Size Reduction
  • Strain Hardening
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25
Q

What is solid solution strengthening?

A

Foreign atoms are introduced to hinder dislocation movement by distorting structure.

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26
Q

What is strengthening by grain size reduction?

A

Increasing number of grain boundaries hence hindering movement of dislocations.

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27
Q

What is Strain Hardening / Cold Working

A

Plastically deforming a metal at low enough temperature so that the atoms cannot rearrange themselves.

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28
Q

What is a Single Crystal?

A

A crystal with perfect repeated arrangement of atoms with same orientation throughout specimen.

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29
Q

What is a Polycrystalline material?

A

A material with many grains with different crystallographic orientations separated by grain boundaries.

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30
Q

What is an isotropic material?

A

Material in which physical properties are independent of direction.

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31
Q

What are anisotropic materials?

A

Material in which physical properties depend on direction.

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32
Q

What are the advantages of larger grain size? (3)

A
  • Higher melting temperature
  • Higher elastic modulus
  • Higher creep resistance
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33
Q

What are advantages of smaller grain size? (2)

A
  • Higher creep
  • Better toughness and strength
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34
Q

What is a phase diagram?

A

Phase diagram in metals represents the physical states and transformations as a function of alloy constituents and temperature.

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35
Q

What is lever rule for liquid phase?

A

S/R+S

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36
Q

What is lever rule for solid phase?

A

R/R+S

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37
Q

What are the two microstructures in Iron-Iron Carbide Phase diagram?

A

Ferrite and Austenite

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38
Q

What are the three points of interest in Iron-Iron Carbide phase diagram and where are they located?

A

Peritectic – Top left intersection

Eutectic – Top right intersection

Eutectoid – Bottom left intersection

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39
Q

Describe Eutectoid

A

0.76% C at 727C

40
Q

What structure is present at Eutectoid?

A

Pearlite: alternating layers of Cementite and Ferrite surrounded by austenite.

41
Q

What are lever rules for hypoeutectoid fraction?

A

Lever rule for perlite: T/T+U

Lever Rule for ferrite: U/T+U

42
Q

What are lever rules for Hypereutectoid fraction?

A

Lever rule for perlite: X/V+X

Lever rule for cementide: V/V+X

43
Q

What are lever rules for total structure?

A

Lever rule for cementide: T/T+U+V+X

Lever rule for ferrite:
U+V+X/T+U+V+X

44
Q

What are the two main groups of heat treatment?

A

Hardening: Very fast cooling up to quenching for non-equilibrium microstructure

Annealing: Slow cooling rates for fully diffused equilibrium maintaining microstructure

45
Q

What three structures can be produced from Austenite by hardening and what is the cooling method used?

A
  • Pearlite: Slow cooling
  • Bainite: Moderate cooling
  • Martensite: Rapid quench
  • Tempered Martensite:
    Rapid quench + reheat
46
Q

What are the six types of annealing?

A
  1. Stress relief annealing
  2. Homogenizing
  3. Coarse grain annealing
  4. Tempering
  5. Normalizing
  6. Spheroidizing
47
Q

What is normalizing?

A

Removal of uneven structures of the microstructure to obtain a constant small uniform grain for an optimum strength and toughness.

48
Q

What is spheroidizing?

A

Heat treatment to make steels more soft and ductile for machining.

49
Q

What is stress relief annealing?

A

Annealing to dismantle internal stress from previous processes and heat treatments.

50
Q

What is homogenizing?

A

Homogenizing of local differences in the microstructure in heterogeneous grain distribution.

51
Q

What is coarse grain annealing?

A

Creation of a large grain structure to improve machinability.

52
Q

What is tempering?

A

Tempering enhances ductility and toughness.

53
Q

What is recrystalization?

A

Process for reverting from cold worked state.

54
Q

What are some properties of Low-Carbon Steels?(6)

A
  • Less than 0.25 % C
  • Ferrite and Pearlite microstructure
  • Strengthening performed by cold work
  • Low strength and hardness, high ductility and toughness
  • Machinable and weldable
  • Cheap
55
Q

What are some properties of medium carbon steels? (3)

A
  • Between 0.25% and 0.6% C
  • Heat treated to improve properties
  • Stronger than low carbon steels, but less toughness and ductility
56
Q

What are some properties of High-carbon steels? (2)

A
  • Between 0.6% and 1.4% wrt C
  • Hardest and strongest but least ductile
57
Q

What are some properties of stainless steels? (3)

A
  • Resistant to corrosion
  • Atleast 11% Chromium
  • High temperature resistance, low creep
58
Q

What are some properties of Aluminum? (7)

A
  • Third most common material
  • Good strength with regard to density
  • High resistance against weather and seawater
  • Good formability and machinability
  • High electrical conductivity
  • High thermal conductivity
59
Q

What are some properties of pure Aluminium? (3)

A
  • High formability
  • Strong corrosion resistance
  • Surface can be polished using electrolysis for reflector applications
60
Q

What are some Aluminum alloying elements and what properties do they improve? (6)

A

Silicon - Increases Castability

Magnesium - Increases strength

Copper - Increases hardenability

Zinc - Increases strength

Manganese - Increases recrystallization temperature

Lithium - Decreases density

61
Q

What are some properties of Copper? (6)

A
  • High electric conductivity
  • High thermal conductivity
  • Strength increased by cold deformation
  • Excellent formability
  • Good weldability and solderability
  • High corrosion resistance
62
Q

What are some properties of pure copper? (3)

A
  • High corrosion resistance
  • Low tensile strength
  • Good conductivity
63
Q

What are the two important copper alloys and what are their compositions?

A

Brass: Copper zinc with less than 50% Copper

Bronze: Copper tin with less than 60% copper

64
Q

What are some properties of Magnesium? (9)

A
  • High availability
  • Low density
  • Low strength
  • Low elasticity
  • Medium cost
  • Excellent machinability
  • Good dampening
  • Good castability
  • Low corrosion resistance
65
Q

What are some properties of Pure Magnesium? (5)

A
  • High reactivity
  • Hexagonal lattice
  • Poor formability
  • Low toughness
  • High notch sensitivity
66
Q

What are some important Magnesium alloying elements and what do they do? (6)

A

Aluminum/Zinc:
- Increase toughness
- Decrease notch
sensitivity

Manganese:
- Increases corrosion
resistance

Cerium/Thorium:
- Increases strength at high
temperature

Zirconium:
- Grain refinement
- Increases formability and
strength

67
Q

What are some properties of Titanium? (6)

A
  • Fourth most common
  • High strength
  • Low density
  • High cost
  • High corrosion resistance
  • High working
    temperature
68
Q

What are some properties of pure titanium? (2)

A
  • Ductile and forgeable
  • Used for corrosion resis.
69
Q

What is alpha and beta titanium?

A

Alpha titanium has hexagonal structure

Beta titanium has cubic space centered structure

70
Q

What is technical titanium?

A

Titanium with portions of iron and oxygen

71
Q

How do properties of technical titanium vary with grade?

A

They are better with grade

71
Q

What are some properties of alpha titanium?(3)

A
  • Low to medium strength
  • Low density
  • Good weldability
72
Q

What are some properties of Nickel? (5)

A
  • Face-Centered Cubic structure
  • High strength
  • Very high density
  • High material cost
  • High working temperature
73
Q

What are some properties of pure nickel? (2)

A
  • Ferromagnetic
  • Corrosion resistant
74
Q

What are some important Nickel alloys and what effect do they have? (5)

A

Copper: Strength

Chromium: Toughness

Cobalt: Wear resistance

Iron: Temperature resistance

Molybdenum: Corrosion resistance

75
Q

What are some properties of Nickel-based super alloys?(5)

A
  • High strength
  • Long fatigue life
  • Resistance against creep
  • Resistance against stress rupture
  • Resistance against corrosion and oxidation
76
Q

What are the three main types of ceramics?

A

Consumer, Functional, and Structural

77
Q

What types of ceramics are included in consumer ceramics?

A

Silicate ceramics

78
Q

What types of ceramics are included in Functional ceramics?

A

Silicate ceramics and non-oxide ceramics.

79
Q

What types of ceramics are included in structural ceramics?

A

Oxide and non-oxide ceramics

80
Q

What are some examples of Silicate ceramics?(3)

A
  • Porcelain
  • Stoneware
  • Glass ceramic
81
Q

What are some examples of Oxide ceramics?(3)

A
  • Aluminum Oxide
  • Zirconium Oxide
  • Titanium Oxide
82
Q

What are some examples of non-oxide ceramics?(3)

A
  • Carbon
  • Boron Carbide
  • Silicon Nitride
83
Q

What are some forming processes for ceramics? (3)

A
  • Pressing
  • Extrusion
  • Injection Molding
84
Q

What are the two general processes for creating ceramics?

A

Forming,
Sintering(burning)

85
Q

What structure do silicate ceramics have after sintering?

A

Glassy and crystalline phases

86
Q

What structure do oxide and non-oxide ceramics have after sintering process?

A

Polycrystalline structure

87
Q

What features dominate the mechanical properties of ceramics?

A

Pores, inclusions, and manufacturing induced defects.

88
Q

What are most common coordination numbers for ceramic materials?

A

4, 6, 8

89
Q

What are some physical and mechanical properties of ceramics? (6)

A
  • Disposition to brittle fracture
  • Low thermal conductivity
  • Low thermal expansion
  • High hardness
  • Low electrical conductivity
  • High corrosion resistance
90
Q

What is used to characterize ceramics instead of tensile strength?

A

Flexural strength

91
Q

What is used to accurately model ceramic behavior and why is it used?

A

Weibull distribution, because of high degree of scatter in properties.

92
Q

What are some rules for construction with ceramics?(5)

A
  • Avoid sharp edges
  • Avoid abrupt changes in cross section
  • Pressure load to be preferred over tensile load
  • Avoid high edge pressure
  • Consider different thermal expansion coefficients
93
Q

What are some important ceramic materials? (3)

A
  • Aluminum Oxide
  • Dense Silicon Nitride
  • Boron Carbide
94
Q

What are some properties of Aluminum Oxide? (5)

A
  • Good mechanical and chemical properties
  • High hardness
  • Disposition to creep at high temperatures
  • High thermal expansion
  • Medium thermal conductivity
95
Q

What are some properties of dense silicon nitride?(3)

A
  • Suitable for high temperature applications
  • Polyphase material
  • Low chemical resistance
96
Q

What are some properties of Boron Carbide? (7)

A
  • Third hardest material in world
  • High hardness at high temperatures
  • Non-oxide, non-metal ceramic
  • Only machinable with diamonds
  • Thermal conductivity decreases with increasing temperature
  • Low oxidation resistance
  • High chemical resistance

Materials Exam Upload (4 decks)

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