5.7C - Uses and properties of metals and alloys

Match properties to the job

Materials are chosen for the job they must do. Ductile metals can be drawn into wires; malleable metals can be hammered or rolled into shape. Electrical conductivity suits a wire, while thermal conductivity suits the base of a cooking pan. Low density keeps the mass small for a given volume.

[DIAGRAM: asset_name: Property-use matching map - diagram 1; asset_slug: 126_5_7c_uses_and_properties_of_metals_and_alloys_diagram1; file: diagram_assets/126_5_7c_uses_and_properties_of_metals_and_alloys_diagram1.png; recommended_method: deterministic_drawn; description: Exact monochrome teaching map showing the reasoning route use asked for -> required property -> suitable metal or alloy, with examples for wiring/copper, aircraft parts/magnalium and jewellery/gold alloy. The diagram is conceptual but label-dependent, so deterministic drawing is used. Nearby prose gives all assessed chemistry for accessibility.]

The map gives three examples of this reasoning. Start with what the object must do, identify the properties needed, then choose a material that supplies them. Several materials may work; the best choice depends on the full set of requirements.

Aluminium and magnalium

Aluminium has low density, so a given volume has less mass than many other metals. It is malleable, conducts electricity and heat, and resists corrosion because of a thin protective aluminium oxide layer. Corrosion resistance does not mean that aluminium is an unreactive metal.

Magnalium is an alloy of aluminium and magnesium. Suitable compositions combine low density with greater strength or hardness than pure aluminium, useful for aircraft or vehicle parts that must be light and withstand forces.