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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 classes of stainless steel as defined by crystalline structure (along with ferritic, martensitic, duplex and precipitation hardened). [1]
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.
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 manganese has an effect similar to nickel, i.e. it stabilizes the austenite phase. Hence, depending on their manganese content, Fe-Mn maraging steels can be fully martensitic after quenching them from the high temperature austenite phase or they can contain retained austenite. [7]
2) Deformation in non-recrystallization regions. Austenite grains are elongated by rolling. Deformation bands might present within the band as well. Elongated grain boundaries and deformation bands are all nucleation sites for ferrite. 3) Deformation in austenite-ferrite two phase region. Ferrite nucleates and austenite are further work-hardened.
Typically Grade EN 1.4462 (also called 2205). It is typical of the mid-range of properties and is perhaps the most used today Super-duplex (PREN range: 38–45) Typically grade EN 1.4410 up to so-called hyper duplex grades (PREN: >45) developed later to meet specific demands of the oil and gas as well as those of the chemical industries.
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 ...
Diffusional transformations like austenite transforming to a cementite and ferrite mixture can be explained using the sigmoidal curve; for example the beginning of pearlitic transformation is represented by the pearlite start (P s) curve. This transformation is complete at P f curve. Nucleation requires an incubation time.