Topic 2: Materials

Question 1

Metals

Answer 1

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

Question 2

Ceramics

Answer 2

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

Question 3

Polymers

Answer 3

Large molecular structure
low density
flexible

Question 4

Composites

Answer 4

Combination of materials from different groups.

Question 5

Interstitial Solution

Answer 5

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

Question 6

Substitutional Solution

Answer 6

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

Question 7

Homogenous

Answer 7

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

Question 8

Heterogenous

Answer 8

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

Question 9

Phase

Answer 9

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

Question 10

Equilibrium

Answer 10

state of a system where the phase characteristics remain constant

Question 11

Alloy

Answer 11

Material composed of at least two different elements

Question 12

Main/parent/base metal

Answer 12

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

Question 13

Impurities

Answer 13

chemical substances that differ from the chemical composition of the material

Question 14

Solid Solubility

Answer 14

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

Question 15

States of matter

Answer 15

gas, liquid.solid

Question 16

Solidification and Cystallisation

Answer 16

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

Question 17

Complete solid solubility

Answer 17

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.

Question 18

Equilibrium cooling

Answer 18

cooling occurs slowly in which the phase equilibrium is maintained.

Question 19

Non-Equilibrium cooling

Answer 19

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.

Question 20

Cored Grains

Answer 20

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

Question 21

Inverse Lever Rule

Answer 21

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.

Question 22

Eutectic Mixtures

Answer 22

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

Question 23

Eutectoid Transformations

Answer 23

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

solid+solid->solid

Question 24

Peritectic changes

Answer 24

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.

Question 25

Complete solid insolubility

Answer 25

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

Question 26

Eutectic point

Answer 26

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

Question 27

Eutectic Structure

Answer 27

alternating layers of two materials with eutectic composition-> Lamella

Question 28

Partial Solid Solubility

Answer 28

Original materials mix to produce a new solid

Question 29

Eutectoid point

Answer 29

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

Question 30

Effect of carbon on steel

Answer 30

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

Question 31

Austenite

Answer 31

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

Question 32

Ferrite

Answer 32

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

Question 33

Cementite

Answer 33

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

Question 34

Pearlite

Answer 34

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

Question 35

Ledeburite

Answer 35

Mixture of 4.3% carbon Eutectic mixture of austenite and cementite

Question 36

Hypoeutectoid steel

Answer 36

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

Question 37

Hypereutectoid steel

Answer 37

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

Question 38

Low carbon steel

Answer 38

0.07-0.15% carbon Uses: Automobile body parts, wire, chains Properties: soft, weak, cold workable, malleable, ductile, low tensile strength

Question 39

Mild carbon steel

Answer 39

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

Question 40

Medium carbon steel

Answer 40

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

Question 41

High carbon steel

Answer 41

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

Question 42

Ultra-high carbon steel

Answer 42

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.

Question 43

Quench Hardening

Answer 43

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

Question 44

Tempering

Answer 44

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

Question 45

Thermoplastic plastics

Answer 45

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.

Question 46

Thermosetting plastics

Answer 46

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

Question 47

Polyethylene

Answer 47

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

Question 48

Polypropylene

Answer 48

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

Question 49

ABS

Answer 49

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

Question 50

PLA

Answer 50

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

Question 51

PVC

Answer 51

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

Question 51

Nylon

Answer 51

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