metals

Question 1

What is the rolling load equation?

Answer 1

F = x.w. sqrt(R.(ho - hf) ).sflow

Question 2

What is extrusion?

Answer 2

A round billet is placed into a chamber and forced through a die opening by a ram
The die dictates the final shape of the product and may be simple (round) or more complex (I-section, T-section etc)
lead is extruded at room temperature

Question 3

What temperature are steel and aluminium extruded at?

Answer 3

steel - 1000-1200°C
aluminium - 350-550°C

Question 4

What is indirect extrusion?

Answer 4

where the die moves towards the billet

Question 5

What is the extrusion ratio equation?

Answer 5

R = Ao/Af

Question 6

What is the extrusion pressure equation?

Answer 6

P/s = a+bLn(R)

Question 7

What is the forging load (upsetting force) equation?

Answer 7

P = s (1+ 2μr/3h)

Question 8

What is open die forging?

Answer 8

the deformation or upsetting of a
normally cylindrical specimen between two platens

Question 9

What is impression die forging?

Answer 9

the material acquires the shape of the die cavities whilst it is being deformed

Question 10

What is a flash in impression die forging?

Answer 10

when some of the material flow sideways

Question 11

What is friction stir welding?

Answer 11

joining metals without the need for filler materials

Question 12

What process is good for small parts?

Answer 12

metal injection moulding

Question 13

What are light elements?

Answer 13

elements with specific gravities of less than 5

Question 14

How do non heat treatable alloys derive their strength?

Answer 14

m refinement of grain size, solid solution
strengthening and cold working

Question 15

What is the purpose of solid solution?

Answer 15

take back into solid solution (dissolve) as
much as possible all the alloy additions that contribute to age hardening
As high a temperature as possible and for as short a time as possible

Question 16

What is the purpose of quenching?

Answer 16

Material quenched after solution treatment stored at low temperature to reduce natural ageing

Question 17

At what temperature is ageing carried out?

Answer 17

100 to 190°C for 8 to 16 hours

Question 18

What is a slip plane?

Answer 18

plane of greatest packing density

Question 19

What is slip direction?

Answer 19

closest-packed direction within a plane

Question 20

Why is ageing important?

Answer 20

form useful
precipitates within
grains

Question 21

What is hot working?

Answer 21

working where T/Tm > 0.6
For lead, deformation at room temp. is actually
warm working (Tm = 327°C)

Question 22

What are the advantages and disadvantages of work hardening?

Answer 22

increase in strength but decrease in ductility

Question 23

What are the benefits of annealing?

Answer 23

increased ductility

Question 24

What are the benefits of reducing grain size?

Answer 24

increase strength and toughness

Question 25

What is Solid Solution Strengthening?

Answer 25

Substitutional atoms are the basis of alloying which is used to improve many properties of metals

Question 26

What is the role of the fibres and the matrix?

Answer 26

The role of the fibres is to carry the load and the role of the matrix is distribute the load to the fibres

Question 27

What is a metal matrix composite made of?

Answer 27

Two components, one the metal matrix, and the other a reinforcement, usually an intermetallic oxide, carbide, or nitride

Question 28

What are connecting rods made from?

Answer 28

aluminium and reinforced with stainless steel fibres

Question 29

What are the advantages of discontinuous MMCs?

Answer 29

Mainly focused on aluminium and silicon carbide High strength High elastic modulus Low sensitivity to changes in T High wear resistance

Question 30

What are the dissadvantages of discontinuous MMCs?

Answer 30

cost Lower fracture toughness than matrix alloy Fabrication and joining problems Thermal fatigue problems

Question 31

When are cluster mills used?

Answer 31

These are very rigid and are used in rolling thin sheet of high strength materials such as stainless steel

Question 32

What causes surface defects?

Answer 32

inclusions in the material, scale, rust or roll markings

Question 33

Why does surface cracking occur from extrusion?

Answer 33

if the extrusion temperatures are either too high or too low, or if the extrusion speed is too high to allow the material to deform

Question 34

what is near net shape forging?

Answer 34

where the part formed is very close to the final required dimensions, and the dies are machined to greater accuracy than in other operations. Aluminium and magnesium are suited to this, as the forging loads are low and there is little die wear

Question 35

What is friction stir welding used for?

Answer 35

wings and fuel tanks

Question 36

Where do non heat treatable alloys derive their strength?

Answer 36

refinement of grain size, solid solution strengthening and cold working

Question 37

Where do heat treatable alloys derive their strength?

Answer 37

precipitation strengthening

Question 38

What is used in upper wing structures?

Answer 38

7xxx Al-Zn

Question 39

Why are vacancies produced?

Answer 39

solidification or a result of atomic vibrations

Question 40

What is the purpose of homogenisation?

Answer 40

Get rid of uneven chemical composition caused by casting

Question 41

Why does strength increase with smaller grain size?

Answer 41

there are more grain boundaries that are more likely to stop the movement of dislocations