Metals & Alloys

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GCSE DT RevisionMetals and Alloys

Key facts

Ferrous metals (contain iron)

Mild steel — iron + ~0.3% carbon. Strong, tough, cheap, malleable. Rusts without protection. Car bodies, general structures, fabrication.
High carbon steel — iron + 0.6–1.4% carbon. Very hard but brittle. Cutting tools, drill bits, springs, files.
Cast iron — iron + 2–4% carbon. Very hard and brittle, cannot be bent. Engine blocks, manhole covers, cookware.
Stainless steel — iron + chromium (+ nickel). Rust resistant, hygienic, attractive. Cutlery, medical instruments, kitchen equipment.
All ferrous metals except stainless steel will rust (corrode) in moist air.

Non-ferrous metals (no iron)

Aluminium — lightweight, good strength-to-weight ratio, corrosion resistant, good conductor. Aircraft, drinks cans, window frames.
Copper — excellent electrical and thermal conductor, malleable, corrosion resistant. Electrical wiring, plumbing, PCB tracks.
Brass (Cu + Zn alloy) — golden appearance, corrosion resistant, machinable. Door fittings, musical instruments, bathroom taps.
Titanium — very high strength, lightweight, excellent corrosion resistance. Aerospace, medical implants. Expensive.

Alloys and why they are harder

An alloy = a mixture of a metal with one or more other elements, improving properties.
Different-sized atoms distort the regular crystal lattice → harder for atom layers to slide → harder and stronger.
Brass (Cu + Zn) — better machinability and corrosion resistance than pure copper.
Bronze (Cu + Sn) — harder than copper. Bearings, statues, medals.
Duralumin (Al + Cu + Mg) — much stronger than pure aluminium. Aircraft structures.
AQA often asks: which alloy/metal for a specific application — always link property to product requirement.

Exam questions — 4 questions · 10 marks · real AQA 8552 past papers

1 markMetal for door handlesAQA 8552 Jun 2024 Q1

A designer needs a metal for decorative door handles — corrosion resistant, golden appearance, easy to machine. Which is most suitable?

A Mild steel

B Brass

C Cast iron

D High carbon steel

1 markFerrous identificationAQA 8552 style

Which of the following is a ferrous metal?

A Aluminium

B Copper

C Mild steel

D Brass

4 marksScrewdriver blade materialAQA 8552 Nov 2021 Q14 style

A screwdriver blade must be hard and durable to turn screws without the tip wearing. Identify a suitable metal and explain why its properties make it appropriate. (4 marks)

Hint: Name a specific metal (high carbon steel / chrome vanadium). Give TWO properties and explain why each matters for a screwdriver.

+40 XP

2 marksWhy alloys are harderAQA 8552 Jun 2022 Q11 style

Explain why alloys are generally harder than the pure metals they are made from. (2 marks)

Hint: Two-mark chain: different-sized atoms → distort lattice → layers cannot slide → harder.

+20 XP

Ferrous metals (contain iron)

Non-ferrous metals (no iron)

Alloys and why they are harder

Module complete!