Titanium

Question 1

What are the sectors that use titanium?

Answer 1

Commercial aerospace
military aerospace
Power generation
CPI and Desalination

Question 2

What are the advantages of titanium?

Answer 2

Low density
Excellent corrosion resistance
High melting point
High specific strength
Compatible with CFRP
Excellent properties at high temperatures

Question 3

What are the disadvantages of Titanium

Answer 3

Expensive to machine
Low wear resistance
Difficult to form
Pick up of oxygen + nitrogen ^ 500*C
Expensive £25k/tonne
lots of work to remove oxygen

Question 4

Why is titanium with CFRP?

Answer 4

Similar linear expansion coefficient
Similar electrochemical potential
Can join easily - no galvonic corrosion
Similar youngs modulus (stifnnes)

Question 5

What is the order of the FFC cambridge process?

Answer 5

1. Tio2 and MeOx
2. Blend
3. Press
4. Sinter
5. Electrochemical process

Question 6

In FFC what are the components of the electrochemical process

Answer 6

Anode - Graphite
Cathode - TiO2/MeOx
Crucible - Titanium
Liquid - molten CaCl2 800-1100*C

Question 7

What process is used for the extraction of titanium?

Answer 7

Kroll Process

Question 8

What are the components of the Kroll process?

Answer 8

1. Rutile + Chlorine + Coke
2. Magnesium and TIckle
3. MgCl2 off product
4. Alloys and scrap added to sponge
5. Electrode
6. Melt process

Question 9

What is the general processing of titanium sponge?

Answer 9

1. Titanium sponge
2. Compaction
3. Manufacture electrodes
4. VAR (vacuum arc remelting)
5. Ingots
6. Breakdown Forging
7. Blooms

Question 10

What are some Alpha-Stabilising elements?

Answer 10

Aluminium
Oxygen
Nitrogen

Question 11

What are the Beta-Stabilising elements?

Answer 11

Molybdenum
Iron
Vanadium
Chromium
Manganese

Question 12

What does increasing Alpha stabilisers do?

Answer 12

Promotes alpha Phase

Question 13

How can you promote the beta phase

Answer 13

Increase the quantity of beta stabilisers

Question 14

What are the properties of Alpha dominant structures?

Answer 14

Higher Creep strength
Improved weldability

Question 15

What are the properties of beta dominant structures?

Answer 15

Higher density
Increased heat treatment response
Higher short term strength
Increased strain rate sensitivity
Improved fabricability

Question 16

What is meant by the beta transus?

Answer 16

The temperature at which titanium alloy transforms from alpha to beta form

Question 17

What temperature is the beta transus

Answer 17

883*C

Question 18

What is the structure of the atoms before and after beta transus

Answer 18

before - BBC
after - HCP

Question 19

What is the effect of increasing interstitial elements on the properties of titanium?

Answer 19

Increases the tensile strength
Decreases the weld joint bend elongation

Question 20

What is the order of interstitial elements in terms of effect on properties?

Answer 20

N > O > C

Question 21

How can Alpha alloys be strengthened?

Answer 21

1. Solution Strengthening from OXYGEN
2. Grain Refinement (Hall Petch)
   3.Cold work

Question 22

What phase are non-heat treatable products?

Answer 22

Alpha
composition is such that beta cannot be retained at room temp in any form.
Always alpha
Martensite formed

Question 23

What are the applications of alpha alloys?

Answer 23

CLadding in chemical plants
Hydraulic piping
Cooling towers

Question 24

What are the benefits of Alpha Alloys

Answer 24

Highly corrosion resistant
Low maintanence cost

Question 25

What are the applications of near alpha alloys?

Answer 25

Compressor disks Compressor blades Gas turbine engines (compressor section)

Question 26

Why are near alpha alloys good for creep resistance?

Answer 26

1. Silicon pins dislocations 2. Large prior beta grain size - inhibits grain boundary sliding 3. Alpha Structure - slow diffusion up to 600*C

Question 27

What are the applications of

Answer 27

Bulk heads for F22 High performance aircraft

Question 28

What are the benefits of Near beta alloys?

Answer 28

Good hardenability

Question 29

Applications of near beta alloys?

Answer 29

Landing gear components Rotor hub for helicopters

Question 30

Benefits of Beta alloys

Answer 30

Cold formable Omega formation surpassed

Question 31

What effect does grain size have on tensile strength?

Answer 31

Determines strength via Hall-Petch grain size reduction ideal Increase phase boundaries interfere with slip . increased Yield Strength

Question 32

what effect do interstitial elements have on tensile strength

Answer 32

Deleterious effect on ductility Have very potent solis solution strenghtening affect.

Question 33

What affect does age hardening have on tensile strength

Answer 33

hinders slip and increases strength.

Question 34

What is the microstructure influence on fracture toughness?

Answer 34

Lenticular morphologies provide a tortuous path for cracks fine grain structure makes crack path easy Fine grain structure have poor fracture toughness

Question 35

Microstructure influence on fatigue

Answer 35

Fine grain structure will have good crack initiaion resistance Once crack has grown, microstructure ideal to have large grains to reduce ease of crack propogation

Question 36

Fatigue crack initiation resistance

Answer 36

Fine grain structure wanted Stop crack initiation

Question 37

what is the most expensive part in the Kroll process

Answer 37

Thermomechanical process

Question 38

Heating Ti-6Al-4V above the beta transus for 4 hours followed by a furnace cool will lead to…

Answer 38

A single colony alpha structure and grain boundary alpha

Question 39

How are medium strength levels generated in CP-Ti alpha alloys?

Answer 39

Cold working