Quenching

Quenching rapidly cools a material to suppress slower transformations and retain or create a particular structure. It is used especially to control the microstructure and properties of metals and alloys.

Cooling curve: A graph showing how a material's temperature changes over time during cooling. Its slope helps describe the cooling rate that governs transformations during a quench.
Martensitic transformation: A diffusionless transformation in which a crystal changes structure through coordinated atomic motion. In steel, quenching can trigger this transformation and produce hard martensite.
Austenitization: Heating steel to form austenite before a heat treatment such as quenching. Steel must usually enter the austenite phase before quenching can form martensite.
Annealing: A heat treatment that heats and slowly cools a material to soften it or refine its structure. Unlike quenching, annealing allows more time for transformations and diffusion.
Quench cracking: Cracking caused by stresses generated during rapid cooling and phase transformation. It is a direct failure mode when quenching stresses exceed a material's strength.
Time-temperature-transformation diagram: A diagram showing when phase transformations occur at constant temperatures over time. It reveals which transformation windows rapid cooling must bypass.
Martensite: A hard, metastable phase formed in some steels by rapid cooling from austenite. It is the principal structure sought when steel is quenched for hardness.
Austenite: A face-centered cubic phase of iron that can dissolve substantial carbon. It is the high-temperature starting phase for many steel quenching treatments.
Normalizing: A steel heat treatment involving austenitization followed by cooling in still air. Air cooling is generally slower than a severe quench and produces different steel structures.
Quench distortion: A change in a workpiece's shape or dimensions during quenching. Uneven cooling and nonuniform transformation can warp a quenched component.

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