Definition
A heat treatment process in which a metal is heated to a specific temperature and then cooled slowly, usually in the furnace or in an insulating material, to soften it, relieve internal stresses, and make it easier to machine, form, or work.
Plain English
Heating a metal up and then letting it cool down very slowly so it becomes softer and easier to bend, cut, or shape.
Context Anchor
Seen in aircraft maintenance and metal repair work, especially when working with sheet metal, tubing, or parts that must be shaped without cracking.
Derivation
From the Old English 'onǣlan,' meaning 'to set on fire' or 'to heat.' The original sense was simply 'to heat'; over time it came to mean the controlled heating and slow cooling used to soften metal, which is exactly the aviation meaning.
Why Pilots Care
Annealed metal behaves differently from hardened metal. A technician who needs to bend or form a part may anneal it first; if the wrong temper is used in a structural location, the part may not have the required strength.
Grounding Statement
Picture a stiff piece of metal being heated and cooled carefully so it relaxes enough to be shaped without splitting.
Intuition Check
Annealing is not just heating a part until it is hot. The correct temperature, time at that temperature, and cooling method are what make it annealing.
Example Sentence 1
The technician annealed the aluminum sheet before forming it around the tight curve of the fairing.
Example Sentence 2
Proper annealing prevents work-hardening cracks during extensive sheet metal repairs.