Website Glossary:
Heat-treatment and Metallurgy Terms
- Alloy – A combination of two or more metals, designed to have properties not found in any single metal.
- Annealing – A heat-treatment process that alters the properties of a material, typically to increase its ductility and reduce its hardness.
- Austenite – A solid solution of carbon in face-centered-cubic (FCC) iron, which exists at high temperatures.
- Bainite – A two-phase microstructure consisting of ferrite and cementite. Formed during certain conditions of isothermal transformation.
- Carburizing – A heat-treatment process where carbon is introduced into the surface layer of a steel.
- Cementite – An iron carbide, Fe₃C, which is a hard and brittle phase found in most steels and cast irons..
- Hardening – The process of making a material harder through heat treatment or alloying.
- Hardness – The resistance of a material to localized deformation.
- Heat Treatment – Controlled heating and cooling processes used to change the structure and properties of metals and alloys.
- Hot rolling – A metalworking process where metals are rolled at temperatures above their recrystallization point.
- Hypo-eutectoid steel – Steel with less than the eutectoid composition of carbon.
- Hypo-eutectic alloy – Alloy with a composition less than the eutectic composition.
- Decarburization – The removal of carbon from the surface layer of a steel when heated in a medium that is not carbon neutral.
- Ductility – The ability of a material to deform plastically before fracturing.
- Eutectic – A mixture of two or more phases that solidifies at a constant temperature.
- Eutectoid – A homogeneous solid solution which, upon cooling, decomposes into two or more new phases at a fixed temperature.
- Ferrite – A phase of iron and small amounts of carbon, with a body-centered-cubic (BCC) structure.
- Grain boundaries – The interface separating two grains, or crystallites, in a polycrystalline material.
- Isothermal transformation – A process in which a material is held at a constant temperature, allowing it to transform structurally over time.
- Martensite – A very hard metastable structure formed by rapid cooling of austenite.
- Normalizing – A heat treatment process that involves heating a material and then allowing it to cool in open air.
- Pearlite – A two-phase lamellar structure in steels, consisting of alternating layers of ferrite and cementite.
- Phase diagram – A graphical representation showing the equilibrium phases as a function of temperature, pressure, and composition.
- Precipitation hardening – A heat treatment technique that involves the precipitate formation of a secondary phase to increase strength and hardness.
- Quenching – Rapid cooling of a material, usually metal, from high temperatures.
- Recrystallization – The formation of a new set of strain-free and equiaxed grains in a material during heating.
- Slag – The byproduct, typically consisting of oxides, silicates, and other compounds, that forms during the smelting of ores.
- Sintering – A process that involves compacting and heating powdered material just below its melting point to form a solid mass.
- Solution heat treatment – Heating an alloy to a temperature where one or more phases dissolve, then cooling rapidly to obtain a supersaturated solution.
- Tempering – A process where previously hardened steel or cast iron is heated to a temperature below the critical point, then cooled, to improve toughness.
- Tensile strength – The resistance of a material to breaking under tension.
- Thermal expansion – The tendency of a material to change in volume or shape with temperature.
- Toughness – The ability of a material to absorb energy and deform without fracturing.
- Transformation temperature – The temperature at which a phase change occurs in a material.
- Work hardening – The strengthening of a metal or polymer by plastic deformation.
- Yield strength – The stress at which a material begins to deform plastically.
- Cold working – Deforming metals below their recrystallization temperature, leading to work hardening.
- Cryogenic treatment – Treating materials at very low temperatures to improve their properties.
- Diffusion – The movement of atoms in a material, leading to homogenization.
- Elastic modulus – The measure of stiffness in a material.
- Homogenization – A heat treatment process that results in a uniform distribution of the constituents or phases within an alloy.
- Intergranular corrosion – Corrosion that occurs along grain boundaries, typically because of impurity segregation.
- Malleability – The ability of a material to be hammered or rolled into thin sheets.
- Reduction atmosphere – An environment where oxidation is chemically unfavorable.
- Retained austenite – Austenite that remains at room temperature after quenching, which can impact the steel’s hardness and strength.
- Solid solution – A homogenous crystalline phase with one or more types of atoms, ions, or molecules in its lattice.
- Supercooling – Cooling a liquid below its freezing point without it becoming solid.
- Twinning – A form of plastic deformation which results in a mirror-image reorientation of part of the crystal lattice.
This glossary provides a foundation for those new to heat-treatment and metallurgy. There are many more terms and nuances to explore within the field, and readers are encouraged to delve deeper into specific areas of interest.
