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engineering qce ea > Topic 2: Materials > Flashcards

Topic 2: Materials Flashcards

1
Q

Metals

A

Good conductors of heat and electricity
Not transparent
lustrous
strong but able to be deformed

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2
Q

Ceramics

A

Godo insulators of electricity and heat
resistant to high temperatures
hard but brittle

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3
Q

Polymers

A

Large molecular structure
low density
flexible

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4
Q

Composites

A

Combination of materials from different groups.

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5
Q

Interstitial Solution

A

solute atoms are small in comparison to solvent atoms. Solute atoms occupy spaces present in the crystal lattice of the solvent

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6
Q

Substitutional Solution

A

Solute atoms take up positions normally occupied by atoms of solvent-> atoms swap or substitute themselves into the lattice. Solute and solvent atoms are same size.

Ordered- atoms occupy similar lattice positions in the structure
Disordered- substitution is random

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7
Q

Homogenous

A

composed of parts/elements that are the same kind-> single phase

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8
Q

Heterogenous

A

composed of parts/elements that are different kinds. Components don’t disperse uniformly.

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9
Q

Phase

A

A homogenous portion of a system-> uniform physical and chemical characteristics that can be physically seperated

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10
Q

Equilibrium

A

state of a system where the phase characteristics remain constant

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11
Q

Alloy

A

Material composed of at least two different elements

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12
Q

Main/parent/base metal

A

most important component in an alloy-> usually over 90% of the alloy material

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13
Q

Impurities

A

chemical substances that differ from the chemical composition of the material

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14
Q

Solid Solubility

A

the extent of a metal to be able to form a solid solution with another metal

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15
Q

States of matter

A

gas, liquid.solid

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16
Q

Solidification and Cystallisation

A
  1. Crystals start nucleation
  2. crystal growth
  3. grains form as crystals grow together
  4. Grain boundaries are formed
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17
Q

Complete solid solubility

A

Two elements re able to become one solution in the solid phase

Former when:
1. Metals have same crystal structure
2. atoms exhibit similar chemical characteristics and are similar in size
3. solid solutions are designated by alpha, beta and gamma.

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18
Q

Equilibrium cooling

A

cooling occurs slowly in which the phase equilibrium is maintained.

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19
Q

Non-Equilibrium cooling

A

Diffusion is used to readjust the composition of solid and liquid phases. During the cooling one metal is more abundant in the centre of the grains as the remaining liquid is richer in the other metal.

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20
Q

Cored Grains

A

Result of Non-Equilibrium/industrial cooling. One metal is more abundant in the centre of the grain.

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21
Q

Inverse Lever Rule

A

Used to calculate proportions of solid and liquid at a temperature.

To find the amount of solid measure the distance from composition to the liquidus

To find the amount of liquid measure the distance from the composition to the solidus.

22
Q

Eutectic Mixtures

A

Formed in an alloy system when two solid phases separate simultaneously at a constant temperature from a single liquid phase.
The phase present in a eutectic mixture are alternating layers of the two pure metals.

solid+solid->liquid

23
Q

Eutectoid Transformations

A

Occurs when an existing single solid phase breaks down into two separate phases which are mixed in the transformed alloy.

solid+solid->solid

24
Q

Peritectic changes

A

During the solidification of a cooling alloy, the solid already formed may react with residual liquid to form another solid solution or compound between the first solid present and the liquid.

25
Q

Complete solid insolubility

A

Contains a eutectic point to indicate the composition to the lowest melting point of alloying elements.
If the complete solid insolubility is in the solid state, the metals won’t mix and will remain separate->eutectic point

26
Q

Eutectic point

A

point on phase diagram indicating chemical composition and temperature corresponding to the lowest melting point of alloying elements.

27
Q

Eutectic Structure

A

alternating layers of two materials with eutectic composition-> Lamella

28
Q

Partial Solid Solubility

A

Original materials mix to produce a new solid

29
Q

Eutectoid point

A

point in aphase diagram indicating the chemical composition and temperature to the location where three solid phases co exist

30
Q

Effect of carbon on steel

A

from the eutectoid composition

as the carbon content decreases, alpha ferrite increases-> causes increased ductility but less strength

as the carbon content increases, cementite increases-> causes increases mechanical strength but less ductility

31
Q

Austenite

A

single phase solid solution
FCC Orientation
can contain up to 2% carbon
exists above eutectoid temperature of 727C
Austinite is denser and has larger holes that ferrite to dissolve more carbon
dense structure has more slip planes-> easily flattened

32
Q

Ferrite

A

Single phase solid solution
BCC orientation
only exists above 1394C
More porous but holes are small-> can only dissolve up to 0.03% carbon
Soft, Ductile, low tensile strength

33
Q

Cementite

A

Is the compound iron carbide
Contains 6.67% carbon
very hard, brittle, low tensile strength, high compressive strength

34
Q

Pearlite

A

Is the eutectoid composition
Contains 0.77% carbon
Alternating bands of ferrite and cementite

35
Q

Ledeburite

A

Mixture of 4.3% carbon
Eutectic mixture of austenite and cementite

36
Q

Hypoeutectoid steel

A

contains less than 0.77% carbon
Consists of pearlite and ferrite at room temp

37
Q

Hypereutectoid steel

A

contains more than 0.77% carbon
Consists of pearlite and cementite at room temp

38
Q

Low carbon steel

A

0.07-0.15% carbon

Uses: Automobile body parts, wire, chains

Properties: soft, weak, cold workable, malleable, ductile, low tensile strength

39
Q

Mild carbon steel

A

0.15-0.3% carbon

Uses: structural plates, brackets, bolts, stampings, forgings, seamless tubes, boiler plate, car wheels

Properties: doesn’t harden well when quenched, weldable, cold workable, strong, ductile, very tough

40
Q

Medium carbon steel

A

0.3-0.6% carbon

Uses: forgings, Automotive components-> crankshafts, axels, gears, train rails, wheels, axles

Properties: can be hot or cold formed, suitable for forging and heat treatment, strong, ductile, tough

41
Q

High carbon steel

A

0.6-1.25% carbon

Uses: Suspension, springs, wires, cutting tools, punches, dies, cables, industrial knives, wear plates

Properties: Heat treatable, Very strong, Very hard

42
Q

Ultra-high carbon steel

A

1.25-2% carbon

Uses: High tempered non industrial knives, punches, ball bearings, roller bearings

Properties: high wear resistance, high impact resistance, very hard, very brittle, high compressive strength.

43
Q

Quench Hardening

A

steel alloys are strengthened and hardened by cooling from high temperatures.

44
Q

Tempering

A

method of heat treatment used on steel allows to achieve higher toughness but hardness is decreased. Also increases the ductility

Tempering is done by heating the hardened material to a temperature below the austenite eutectoid temperature.
Heating above the eutectoid temperature will destroy the hard martensite achieved from quenching

45
Q

Thermoplastic plastics

A

made of lines of long chain molecules with few cross linkage
allows softening when heated so that they can be bent into different shapes and become stiff when cooled.

46
Q

Thermosetting plastics

A

made of molecules that are heavily cross linked.
Creates a rigid structure that becomes permanently stiff and solid.

47
Q

Polyethylene

A

Properties: tough, flexible, low density, very chemical and electrical resistant, non toxic, easily moulded, heat sealable. wide colour range

Uses: plastic containers, water pipes, cable insulation

48
Q

Polypropylene

A

Properties: strong, tough, flexible, high impact resistance, high electrical, chemical, and heat resistance, medium density, easily moulded, chrome platable

Uses: Lab equipment, electronics, Automotive products-> instrument panels, sheathing cables, carpet

49
Q

ABS

A

Properties: high impact and tensile strength, absorbs and redistributes energy on impact, good chemical, weather and UV resistance, very tough, hard, wide colour range, chrome platable

Uses: automotive body parts, household electronics, electrical appliances, business equipment

50
Q

PLA

A

Properties:carbon neutral, non toxic, dissolvable with organic solvents, high tensile strength, smooth appearance, castable, low melting point, weldable, transparent

Uses: Automotive interiors, medical implants-> screws, plats, pins, rods, mesh

51
Q

PVC

A

Properties: High tensile strength, tough, good impact and abrasion resistance, hardness can be controlled, flexible, poor conductivity, nonflammable, can be transparent or coloured, good chemical resistance

Uses: automobile parts-> instrument panels, sun visor, seat coverings, mud flaps, floor coverings, drain pipes, furniture, Electronic equipment-> insulation, bedding

51
Q

Nylon

A

Properties: strong, good abrasion, heat, and electrical resistance, resists petroleum oils and solvents, translucent, wide colour range, flexible, can operate at high temperatures, able to be moulded

Uses: Gears, rollers, guides, bearings, wear pads

engineering qce ea (3 decks)

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