Non-Ferrous Materials
Aluminium, titanium, magnesium, copper and nickel alloys, age hardening and their aircraft uses.
Non-ferrous materials, summary notes
- Aluminium alloys are the primary airframe material for their strength-to-weight ratio. 2024 (Al-Cu, 'duralumin') is a high-strength structural alloy; 7075 (Al-Zn) is stronger still; both need corrosion protection such as Alclad (a pure-aluminium cladding) or anodising.
- Heat-treatable aluminium alloys gain strength by precipitation (age) hardening: solution heat-treat, quench, then age naturally or artificially, strength develops over hours/days, which is why 2024 rivets are kept refrigerated to stay soft until driven.
- Titanium alloys give an excellent strength-to-weight ratio, outstanding corrosion resistance and retain strength at high temperature, used for firewalls, engine parts and highly loaded structure; they are expensive and harder to machine.
- Magnesium is the lightest structural metal, used in castings (gearboxes, wheels), but corrodes readily and is flammable as fine chips or powder, it needs careful protection and special fire precautions.
- Copper alloys (brass, bronze) serve as bushes, bearings and electrical parts; nickel alloys (Inconel, Nimonic) handle the highest engine temperatures.
- ⚠ Exam trap: a magnesium fire must NOT be fought with water (it reacts and spreads), use a dry powder/class-D agent. And heat-treatable alloys (2024/7075) age with time, whereas non-heat-treatable alloys (1100/5052) are strengthened only by work (cold) hardening.
Why are 2024-T (DD) aluminium alloy rivets stored in a freezer, and what happens if they are left on the bench too long?
2024 is a heat-treatable alloy that age-hardens at room temperature. After solution treatment it is kept refrigerated ('ice-box' rivets) to slow ageing so it stays soft enough to drive. Left out, it hardens; once it has aged past the drive-time limit it must be re-solution-treated or it will crack when bucked.
Non-ferrous materials concept map
Non-Ferrous Materials
Non-ferrous materials quiz
Non-Ferrous Materials, quiz
1. The main alloying element that gives duralumin its strength is:
CopperZincLead2. Titanium alloys are chosen for hot structure because they:
Keep their strength at high temperature and resist corrosionAre the cheapest metal available for the duty, which is why they displaced steel in hot areasConduct heat better than any other structural alloy, carrying it away from the hot section3. The primary airframe material chosen for its strength-to-weight ratio is:
Aluminium alloyCast ironLead4. 'Alclad' aluminium sheet is protected by:
A cladding of pure aluminiumA layer of steelA coat of magnesium5. 2024 and 7075 aluminium alloys gain strength by:
Precipitation (age) hardeningSimple cold rolling onlyAdding carbon6. Titanium is prized for structure and engine parts because it:
Has high strength-to-weight and keeps strength when hotIs very cheap to produce and machine, which is why it has displaced steel in so many applicationsIs strongly magnetic, allowing simple magnetic particle inspection of finished components7. A magnesium fire should be extinguished with:
A dry powder (class D) agent, not waterWaterA CO₂ jet of water8. Magnesium alloys are mainly used because they are:
The lightest structural metalThe most corrosion-resistantThe strongest metal available