Definition
A controlled heat-treatment process applied to a hardened metal in which the metal is reheated to a specific temperature below its critical point, held there, and then cooled. Tempering reduces the brittleness produced by hardening and produces a balance of hardness, strength, and toughness suited to the part's intended use.
Plain English
Tempering is a way of reheating a hardened piece of metal to a chosen temperature so it becomes less brittle and tougher, while keeping most of its strength.
Context Anchor
Seen in aircraft maintenance, sheet-metal repair, and material specifications for parts such as aluminum skin, brackets, and fittings.
Derivation
From the Latin temperare, meaning 'to mix in proper proportion' or 'to moderate.' In metalwork the word kept that idea -- tempering moderates the extreme hardness of a freshly hardened part so the metal is balanced rather than brittle.
Why Pilots Care
Many aircraft components rely on a specific temper for safe service. A part that has been overheated in service or during repair can lose its temper, becoming weaker or more brittle than the design requires, which can lead to failure under load.
Intuition Check
Temper does not mean anger or mood here. In aircraft materials, it means the physical condition of a metal after it has been treated to give it certain strength and hardness.
Example Sentence 1
After hardening the steel, the technician tempered it at the specified temperature to reduce brittleness before returning the part to service.
Example Sentence 2
Before installing the bracket, verify the material certification lists the correct temper to avoid using an annealed piece in a high-load area.