6.2 Flashcards
Why is titanium used?
High strength, light weight, good temperature and corrosion resistance
How much lighter is titanium compared to steel?
56%
The strength of titanium is maintained to what temperatures?
800F (427C)
What temperatures must titanium be protected?
1000F (583C)
Why must you have a fire extinguisher when working with titanium?
Because sparks will ignite titanium dust
What temperature will titanium ignite at when oxygen is present?
1950F (1065C)
Why is pure aluminium highly corrosion resistant?
Because it forms a non-porous oxide coating
Why must pure aluminium be alloyed?
Because its too soft in a pure form
What are most structural aircraft parts made from?
Heat-treated aluminium alloys
What is alloying?
Mixing aluminium with with other metals to make it stronger
Wrought and cast aluminium’s are identified by a four digit number, designated by who?
Aluminium association of America
What is the wrought and cast aluminium’s identification system called?
AA-numbers
What is the first digit in the AA-number represent?
The major alloying element
What is the second digit in the AA-number represent?
Alloying modification
What do the last two digits in the AA-number represent?
Alloy designator
Aluminium is how much lighter than steel?
Three times lighter
How much more electrical conductivity does aluminium have compared too copper?
Twice as much
Why is remelting aluminium so efficient?
Because it remains un-charged
How much energy is needed to remelt aluminium compared to production?
5%
How is cladding of aluminium alloys completed?
Thin layers are rolled on all sides at high temperature
What is the thickness of clad layers?
3-5% of the material thickness
What does the direction of text on ALclad indicate?
Direction of grain structure
What is cladding usually made from?
Pure aluminium with 1% zinc
What is special about the 1000 series in aluminium designation?
10xx means 99% and xx54 means 0.54% (1054=99.54%)
What is work hardening also known as?
Strain hardening or cold working
What is work hardening ?
Strengthening of a metal by plastic deformation
What’s the time frame from furnace to quench?
10 seconds
Why does quenching of aluminium needs to be done quickly?
Because its alloying metals begin to precipitate from the base metal
What are aluminium alloys heated in?
Molten sodium, potassium nitrate bath, hot-air furnace
What are the three ways to harden alloy after it has been heated and quenched?
- cold working
- natural age hardening
- artificial ageing
What is natural age hardening?
When left at room temperature for days to allow the alloy to precipitate at the grain boundary
What is artificial ageing?
When the temperature is raised which increases the precipitation at the grain boundary
How can age hardening be slowed down?
By freezing the alloy immediately after quenching
How many times can clad material be heat-treated?
3
Why can you only use heat treatment processes a certain amount of times on clad material?
Because small amounts of alloying agents can precipitate out into the clad layer causing corrosion
What does F stand for in basic heat treatment designation?
As fabricated
What does O stand for in the basic heat treatment designation?
Annealed
What does H stand for in the basic heat treatment designation?
Strain hardened
What does W stand for in basic heat treatment designation?
Solution heat-treated
What does T stand for in the basic heat treatment designation?
Heat-treated to produce stable tempers other than F, O, or H
In the basic heat treatment designation what is T followed by?
Numbers 1 to 10 depending on type of heat-treatment
How are non-heat treatment alloys hardened?
By cold working/ strain hardening
For non-heat treatable alloys what are the second digits and what do they represent?
Hx2= 1/4 hard Hx4= 1/2 hard Hx6= 3/4 hard Hx8= full hard Hx9= extra hard
What are the three reasons magnesium is rarely used on aircraft today?
- highly corrosive
- difficult to work with
- highly flammable
Why is pure magnesium alloyed with other elements used?
It is 2/3 the weight of aluminium and its not magnetic
Where is magnesium mostly used on an aircraft?
Instrument casings
Because magnesium has no classification system due to international acceptance, what is mostly used instead?
American society for testing materials (ASTM)
What is used to put out a magnesium fire?
Noble gases (helium or argon) or sand
What are the three heat treatments for magnesium alloys?
- solution treatment (T4)
- precipitation hardening (T5)
- annealing (T6)
Why must magnesium never be heated in a salt bath?
It may result in an explosion
What is GLARE?
GLAss REinforced Laminate
What are fibre metal laminates (FMLs)?
Material consisting of thin layers of metal sheets and uni-directional fibre layers
What is the range of thickness for the aluminium in GLARE?
0.2-0.5mm
What determines the grade of GLARE?
The number of epoxy prepreg layers
What are the three parts of the laminate coding system?
E.g 4B-4/3-0.4
1st= fibre grade and orientation
2nd= X layers of aluminium / X layers of fibre
3rd= aluminium layer thickness (mm)
E.g 4B-4/3-0.4
Where is GLARE mostly used?
- fuselage skin material
- blast resistant containers
- cargo floors and liners
What are the advantages of fibre metal laminates?
- high strength
- fatigue resistant
- damage tolerant
- impact and blast resistant
- fire resistant
- thermal isolation
What are the two functions of a leading edge?
Maintain the right aerodynamic shape and to protect the aircraft
What is a blast resistant container (FAP) made from?
Glare with an aluminium frame
