CASA06A-Non-Ferrous Metals

What defines a non-ferrous metal?

A metal that has an element other than iron as its base

What are the four most common alloying elements for aluminium?

Copper, magnesium, manganese and zinc

What are the two main classes of aluminium alloys?

Wrought alloys (rolled from ingot or extruded) and cast alloys (poured into moulds)

What does the 1xxx aluminium series indicate?

Minimum 99% pure aluminium with no major alloying element. Strain-hardenable with high formability, corrosion resistance and electrical conductivity

What is the major alloying element in the 2xxx series and what is the main drawback?

Copper. Susceptible to intergranular corrosion when improperly heat-treated

What are the two most commonly used 2xxx alloys in aircraft skins and rivets?

2017 and 2024

What is the 3xxx series alloyed with and is it heat-treatable?

Manganese. Generally non-heat-treatable. Most common is 3003 offering moderate strength and good working characteristics

What is the 4xxx series alloyed with and what is its key property?

Silicon. Lowers melting temperature making it suitable for welding and brazing

What is the 5xxx series alloyed with and what are its properties?

Magnesium. Good welding and corrosion resistance. Susceptibility to corrosion increases with high temperatures or excessive cold-working

What is the 6xxx series and its properties?

Magnesium and silicon. Medium strength with good forming and corrosion-resistance properties

What is the 7xxx series alloyed with and what is it used for?

Zinc. Used where high strength and little forming is required

Give examples of 7xxx alloy applications on a medium passenger aircraft

7075: frames, stringers, keel, floor beams, wing ribs. 7079: bulkheads, window frames, landing gear beam. 7178: wing upper skin, spars, beams. 7175: landing gear beam. 7055: wing lower skin

What is the 8xxx series used for?

Aerospace applications requiring exceptionally high strength and stiffness combined to reduce component weight

What is Alclad and why is it used?

Pure aluminium coating rolled onto both surfaces of heat-treated aluminium alloy sheet. Greatly increases corrosion resistance. If penetrated the alloy beneath is exposed to corrosion. Scratches and abrasions must be avoided

What are the two types of heat treatment used on aluminium alloys?

Solution heat treatment and precipitation heat treatment

What is solution heat treatment?

Heating aluminium alloy in a recirculating hot-air furnace to just below melting point until the alloying element is uniform throughout then quenching rapidly within approximately 10 seconds

Why must quenching occur within 10 seconds of removing aluminium from the furnace?

As the metal cools alloying metals begin to precipitate out. If not stopped large grains form and weaken the alloy causing intergranular corrosion

What quenching medium is used for aluminium alloys?

A water bath

How long does it take solution heat-treated aluminium to reach full strength?

Four to five days. Starts to harden within 30 minutes of quenching

What is precipitation heat treatment?

Also called artificial ageing or age hardening. Carried out after solution heat treatment in an oven at lower temperature for a longer period. No quenching required

What is annealing of aluminium?

Raising temperature to annealing temperature and holding until heat-soaked then cooling. Softens the metal and decreases internal stress

Why must clad aluminium be heated quickly during annealing?

Excessive heat causes core material to mix with the cladding reducing corrosion resistance

How many heat treatments can clad aluminium generally receive?

No more than three as repeated treatments diffuse core material into cladding decreasing corrosion resistance

What does the T temper designation mean?

Heat treatment temper. One or more Arabic numerals follow T to specify the exact process

What does T3 mean?

Solution heat-treated followed by strain-hardening. A second digit indicates the amount of strain-hardening

What does T6 mean?

Solution heat-treated followed by artificial ageing (precipitation heat-treated)

What does T42 mean?

Solution heat-treated followed by natural ageing at room temperature to a stable condition. Carried out in the workplace

What does T5 mean?

Artificially aged after being rapidly cooled during a fabrication process such as extrusion or casting

What does the H temper designation mean?

Work hardening temper. Strength improved through work hardening with or without subsequent heat treatment

What does H1 mean?

Simple work hardening only with no additional heat treatment

What does H2 mean?

Work hardened beyond requirement then strength reduced by incomplete annealing to specified level

What does H3 mean?

Work hardened then stabilised by low temperature heat treatment

What does H4 mean?

Work hardened then undergoes incomplete annealing caused by painting after work hardening

What does the O temper designation mean?

Annealed condition. Lowest strength after complete annealing

What does the W temper designation mean?

Solution heat treatment temper. Unstable temper applicable to alloys naturally aged at room temperature after solution heat treatment

What does the F temper designation mean?

Free machining temper. No special requirements for work hardening or heat treatment. Mechanical properties not specified

What does the digit after H1/H2/H3 indicate?

Degree of strain-hardening. Number 8 represents maximum tensile strength. O indicates annealed state

What is strain-hardening (cold-working)?

Mechanically working metal below its critical temperature range by rolling, drawing or pressing. Alters grain structure and hardens the metal

Which aluminium series are non-heat-treatable?

1000, 3000, 4000 and 5000 series. Properties adjusted by cold work or cold-rolling

What are the drawbacks of using magnesium in aircraft?

High susceptibility to corrosion. Tendency to crack when formed (overcome by heating during forming). Readily burns in dust or particle form

How do you extinguish a magnesium fire?

Smother with dry sand or other dry material that excludes air. Never use water as it intensifies the fire

What does solution heat treatment do to magnesium alloys?

Increases tensile strength, ductility and resistance to shock

What does precipitation heat treatment do to magnesium alloys after solution heat treatment?

Increases hardness and yield strength

What are the key properties of titanium?

Lightweight, very high strength, excellent corrosion resistance especially to salt water. Sensitive to nitrogen and oxygen at high temperatures becoming brittle

What percentage of titanium is used in modern jet transport structural areas?

10% to 15%

What are the two most commonly used nickel alloys in aircraft?

Monel and Inconel

What is Monel composed of and where is it used?

Nickel and copper with small amounts of iron and manganese. Used in gears, exhaust systems and high-strength corrosion-resistant applications. Can be welded

What is Inconel composed of and where is it used?

Nickel and chromium with small amounts of iron. Used in turbine engines including nozzle supports, fan casings and blades due to high strength and corrosion resistance at extreme temperatures

How do you differentiate between Inconel and stainless steel?

They are similar in appearance. Differentiation requires a chemical test

What are the three primary copper alloys used on aircraft?

Brass (copper and zinc) for electrical components. Bronze (copper and tin) for bushings, bearings, fuel metering valves and valve seats. Beryllium copper for diaphragms, precision bearings and spring washers

Why is beryllium copper classified as a hazardous material?

Grinding dust or fumes produce airborne contaminants. Identified in Safety Data Sheets

Why is copper primarily used for electrical wiring in aircraft?

Excellent electrical and thermal conductivit