Materials, Properties and Selection of Metals
What the domain tests
Materials, Properties and Selection of Metals tests your ability to classify ferrous and nonferrous metals, relate properties to service conditions, and choose a material for a stated component. Expect questions on carbon content, alloying, identification tests and heat-treatment response.
Core rules
- Ferrous metals contain iron; nonferrous metals do not. Plain carbon steels are classified by carbon content: low carbon (up to about 0.3%), medium carbon (0.3–0.6%) and high carbon (0.6–1.0%).
- Strength resists load; hardness resists indentation and abrasion; ductility allows drawing; malleability allows shaping by hammering; toughness absorbs impact; conductivity carries heat or electricity.
- Alloying changes properties: stainless steel contains chromium for corrosion resistance; brass is copper-zinc; bronze is copper-tin; aluminium alloys are light and corrosion resistant.
- Select by function, load, environment, manufacturing process and cost, not by “strongest” alone.
Worked example
A cold chisel must hold a sharp edge while surviving hammer blows. Mild steel is ductile but too soft, so it would blunt. A medium- or high-carbon steel (about 0.6–0.8% C) can be hardened and tempered: hard at the cutting edge, tougher at the struck end. The selection is justified by hardness, wear resistance and controlled toughness.
Traps
Do not confuse hardness with toughness, or say stainless steel never corrodes. Do not choose high-carbon steel for a welded bracket without considering weldability. In identification, a magnet proves only ferromagnetic behaviour, not exact composition; spark and file tests need experience.