Austeniidne

Austeniidne refers to a phase of iron or steel that is stable at high temperatures. It is named after Sir William Chandler Roberts-Austen, a British metallurgist. Austeniidne is a solid solution of carbon in gamma-iron (γ-Fe), which has a face-centered cubic (FCC) crystal structure. This structure allows a greater amount of carbon to dissolve in the iron compared to ferrite, the phase stable at lower temperatures.

The transformation of iron and steel into austeniidne occurs upon heating above a specific temperature, which depends on the carbon content. For pure iron, this transformation begins at 912 degrees Celsius. The presence of alloying elements can significantly alter the temperature range in which austeniidne is stable. For example, nickel and manganese tend to expand the austeniidne phase field, while chromium and molybdenum tend to contract it.

Austeniidne is generally non-magnetic and is known for its ductility and toughness. It is a critical phase in the heat treatment of steel. When steel is heated into the austeniidne phase and then rapidly cooled (quenched), various hardened microstructures such as martensite can form. Conversely, slower cooling allows for the formation of other phases like pearlite or bainite, which have different properties. The ability to form austeniidne and its subsequent transformations are fundamental to achieving the desired mechanical properties in many steel alloys.