Introduction to materials

Question 1

What is materials science?

Answer 1

The use of materials and our ability to exploit our environment

Question 2

Human history is divided by technological sophistication in creating tools. Name the different ages…

Answer 2

Paleolithic

Mesolithic

Neolithic

Chalcolithic

Bronze age

Iron age

Question 3

What are intrinsic material properties dictated by?

Answer 3

Atomic structure and crystal formation

Question 4

What does the atomic scale dictate?

Answer 4

reactivity of the material, density, reflectivity, thermal and electrical conductivity

Question 5

What does the crystal scale dictate?

Answer 5

Mechanical properties:

ductility, what loads it can withstand without yielding

Question 6

What can control the overall properties of a product made from the material being processed?

Answer 6

The size and directionality of the crystals, presence of any unexpected features, e.g. inclusions

Question 7

What influence does the scale of a material have

Answer 7

The finer the scale the, least influence we can have

atomic bonding is fixed

crystal structure can be influenced by processing, can dictate the conditions that prevent the formation of crystals leading to noncrystalline or amorphous materials

we can do more to influence the growth of crystals and the phases the form, having greater effect on the properties of a material.

Question 8

What are the classifications of materials?

Answer 8

• Metals, ductile with high electrical and thermal conductivities
• Polymers, soft and viscous and low mp
• Ceramics, brittle and high mp
• Composites, comprised of particles or fibres of one type of a retrial embedded in another

Question 9

Properties of Metals

Answer 9

• High mp (up to 1536 oC for Fe)
• Can be casted
• Ductile, due to metallic bonding and atomic packing, can be readily deformed = rolling, deformation is easier if material is hotter –> reduces yield stress = easier plastic deformation requiring less force
• Forging
• Extrusion
• Machining
• Welding

Question 10

Forging?

Answer 10

Metal is deformed to a new shape by the application of force

Question 11

Extrusion?

Answer 11

Metal is forced through a die to form a new cross-section , and drawing, to make cup-shaped objects

Question 12

Machining?

Answer 12

(plastic deformation process), machine tool deforms the workpiece resulting in pieces of metal being sheared away which break off

Question 13

Welding?

Answer 13

Low mp, so can locally melt and allows molten parts to mix together so when they solidify they are a single component

Question 14

What are the properties of Polymers?

Answer 14

• low mp compared to metals (few 100 oC)
• combustible
• v. viscous in liquid state
• can be plastically deformed
• Commonly extruded, made into shapes and sheets and be welded to metals
• v. viscous therefore can’t be cast, but can be squeezed –> injected into die or rolled into sheet
• low thermal conductivity

Question 15

Viscous?

Answer 15

liquid polymers can support their own shape while in the liquid phase, leading to shaping processes that could not be applied to metals, e.g. blowing to make polymer bottles

Question 16

Low thermal Conductivity?

Answer 16

not easily uniformly melted, rapping heating can lead to localised combustion instead –> other heating methods with good mixing required

Question 17

What are the properties of ceramics?

Answer 17

• High mp, cannot be cast
• Brittle (not ductile), cannot be plastically deformed
• Shaped using powder processing
• worked in a slurry

Question 18

Powder processing of ceramics?

Answer 18

ceramics are reduced to powders which are moulded into the required shape and then heated. At a high enough T, powders bond (sinter) to form a dense product

Question 19

Working ceramics in a slurry

Answer 19

slurry is poured into a mould and then carrier liquid is drawn off to leave a viscous layer at the surface, to be removed then sintered or fired. ceramics can be treated like liquids despite different properties

Question 20

What are composites?

Answer 20

Mixtures of different materials

Question 21

What is the reinforcement used for composites?

Answer 21

Can be either particulate or whisker form, and be introduced into a matrix of metals, polymers and ceramics

Question 22

What is the result of a composite?

Answer 22

New material, with mixture of properties from reinforcement and matrix material

Question 23

Name 2 examples of composites

Answer 23

1. GRF ( glass- reinforced plastic), matrix of resin into which glass fibres are mixed
2. MMCs (metal-matrix composites) a mixture of ceramic particles in a metal matrix

Question 24

Name the 3 material structures that influence properties

Answer 24

Atomic bond

Atomic packing arrangement

Micro or macro structure

Question 25

What structures combine to give the overall properties of metals?

Answer 25

mp, ductility - metallic bond that keeps the atoms together

ductility - atomic packing

Question 26

What structures combine to give the overall properties of Polymers?

Answer 26

low mp - covalent bonding

deformability - molecular architecture, long chain molecules

Question 27

What structures combine to give the overall properties of Ceramics ?

Answer 27

high mp, lack of ductility- ionic nature of bonding

Question 28

Do the processing methods have a bearing on the properties obtained?

Answer 28

Yes

Question 29

How can the macro and microstructure of materials be changed?

Answer 29

Processing operation

Question 30

Process operations involving metals

Answer 30

shaping - heating = phase changes that alter the microstructure , hence strength

Question 31

Process operations involving polymers

Answer 31

changes the amount of crystallinity (microstructure) , alters the polymer strength

Question 32

Process operations involving ceramics

Answer 32

sintering - has variable effect on the removal of pores that naturally occur between powder particles packed together. Amount of piers alters mechanical properties

Question 33

What is archaeomaterials?

Answer 33

science of the study of how materials were exploited in the past

extends to study of material original’s, extraction form ore, trading, processing, structure, and subsequent properties