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Austenite, also known as gamma-phase iron (γ-Fe), is a metallic, non-magnetic allotrope of iron or a solid solution of iron with an alloying element. [1] In plain-carbon steel , austenite exists above the critical eutectoid temperature of 1000 K (727 °C); other alloys of steel have different eutectoid temperatures.
Convergent beam electron diffraction (CBED) transmission electron micrograph of a [111] zone axis of austenitic stainless steel. Austenitic stainless steel is one of the five families of stainless steel (along with ferritic, martensitic, duplex and precipitation hardened). [1]
In steel it produces a bainite microstructure whereas in cast irons it produces a structure of acicular ferrite and high carbon, stabilized austenite known as ausferrite. It is primarily used to improve mechanical properties or reduce / eliminate distortion. Austempering is defined by both the process and the resultant microstructure.
The properties of steel depend on its microstructure: the arrangement of different phases, some harder, some with greater ductility. At the atomic level, the four phases of auto steel include martensite (the hardest yet most brittle), bainite (less hard), ferrite (more ductile), and austenite (the most ductile). The phases are arranged by ...
For a eutectoid steel (0.76% C), between 6 and 10% of austenite, called retained austenite, will remain. The percentage of retained austenite increases from insignificant for less than 0.6% C steel, to 13% retained austenite at 0.95% C and 30–47% retained austenite for a 1.4% carbon steel. A very rapid quench is essential to create martensite.
The large radius prevents the propagation of cracks in the material, further resulting in high ductility and good fatigue properties in the material. Some of the austenite phase mentioned above is mechanically metastable and will form martensite when subjected to high stress. The combination of hard, wear-resistant martensite with ausferrite ...
Mechanical properties at room temperature of solution-annealed austenitic–ferritic stainless steels ISO desig. EN num. 0.2% proof stress, min Ultimate tensile strength Elongation, min (%) X2CrNiN23-4 1.4362 400 MPa (58 ksi) 600 to 830 MPa (87 to 120 ksi) 25 X2CrNiMoN22-5-3 1.4462 450 MPa (65 ksi) 650 to 880 MPa (94 to 128 ksi) 25
Carbon content has a strong influence on room temperature strength and thus the specified minimum tensile properties of 304L are 34 MPa (5,000 psi) lower than for 304. However, nitrogen also has a strong influence on room temperature strength and a tiny addition of nitrogen produces 304L with the same tensile strength as 304.