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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.
Its primary crystalline structure is austenite (face-centered cubic). Such steels are not hardenable by heat treatment and are essentially non-magnetic. [2] This structure is achieved by adding enough austenite-stabilizing elements such as nickel, manganese and nitrogen.
The specific cooling rate that is necessary to avoid the formation of pearlite is a product of the chemistry of the austenite phase and thus the alloy being processed. The actual cooling rate is a product of both the quench severity, which is influenced by quench media, agitation, load (quenchant ratio, etc.), and the thickness and geometry of ...
Microstructures of four kinds of duplex stainless steel in each direction. Duplex stainless steels are usually divided into three groups based on their pitting corrosion resistance, characterised by the pitting resistance equivalence number, PREN = %Cr + 3.3 %Mo + 16 %N.
Austenite is gamma-phase iron (γ-Fe), a solid solution of iron and alloying elements. As a result of the quenching, the face-centered cubic austenite transforms to a highly strained body-centered tetragonal form called martensite that is supersaturated with carbon. The shear deformations that result produce a large number of dislocations ...
Austenite has much higher stacking-fault energy than martensite or pearlite, lowering the wear resistance and increasing the chances of galling, although some or most of the retained austenite can be transformed into martensite by cold and cryogenic treatments prior to tempering.
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 results in good wear properties, as the regions near a crack tip strengthen and prevent further propagation.
Austenite exhibits a face-centered cubic (FCC) unit cell, whereas the transformation to martensite entails a distortion of this cube into a body-centered tetragonal shape (BCT). This transformation occurs due to a displacive process, where interstitial carbon atoms lack the time to diffuse out. [ 5 ]