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and then working by plastic deformations to reductions of cross section area between 20% and 40% of the original. The process produces dislocation densities up to 10/cm. The great number of dislocations, combined with precipitates that originate and pin the dislocations in place, produces a very hard
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that interfere with cementite nucleation, but more often than not, the nucleation is allowed to proceed to relieve stresses. Since quenching can be difficult to control, many steels are quenched to produce an overabundance of martensite, then tempered to gradually reduce its concentration until the
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and is called lath martensite. For steel with greater than 1% carbon, it will form a plate-like structure called plate martensite. Between those two percentages, the physical appearance of the grains is a mix of the two. The strength of the martensite is reduced as the amount of retained austenite
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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
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of the iron-carbon system because it is not an equilibrium phase. Equilibrium phases form by slow cooling rates that allow sufficient time for diffusion, whereas martensite is usually formed by very high cooling rates. Since chemical processes (the attainment of equilibrium) accelerate at higher
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essential to create martensite. For a eutectoid carbon steel of thin section, if the quench starting at 750 °C and ending at 450 °C takes place in 0.7 seconds (a rate of 430 °C/s) no pearlite will form, and the steel will be martensitic with small amounts of retained austenite.
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temperatures. Martensite has a lower density than austenite, so that the martensitic transformation results in a relative change of volume. Of considerably greater importance than the volume change is the
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preferred structure for the intended application is achieved. The needle-like microstructure of martensite leads to brittle behavior of the material. Too much martensite leaves steel
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grows. If the cooling rate is slower than the critical cooling rate, some amount of pearlite will form, starting at the grain boundaries where it will grow into the grains until the M
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because the process is a diffusionless transformation, which results in the subtle but rapid rearrangement of atomic positions, and has been known to occur even at
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at such a high rate that carbon atoms do not have time to diffuse out of the crystal structure in large enough quantities to form
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temperature is reached, then the remaining austenite transforms into martensite at about half the speed of sound in steel.
501:(in German and English), vol. 1 (1 ed.), Leuven, Belgium: A.Q. Khan, University of Leuven, Belgium, p. 300
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PTCLab---Capable of calculating martensite crystallography with single shear or double shear theory
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New book for free download, on Theory of
Transformations in Steels, the University of Cambridge
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temperature, martensite is easily destroyed by the application of heat. This process is called
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Lecture by Prof. HDKH Bhadeshia , from the University of Cambridge
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Metallurgy for the Non-Metallurgist from the
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C). Austenite is gamma-phase iron (Îł-Fe), a solid solution of iron and
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Comprehensive resources on martensite from the
University of Cambridge
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The effect of morphology on the strength of copper-based martensites
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steel. This property is frequently used in toughened ceramics like
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For steel with 0–0.6% carbon, the martensite has the appearance of
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622:(with corrections ed.). London: Institute of Materials.
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The growth of martensite phase requires very little thermal
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is reached, at which time the transformation is completed.
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Marks' Standard
Handbook for Mechanical Engineers, 8th ed
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594:(with corrections ed.). Oxford: Pergamon Press.
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0.35% carbon steel, water-quenched from 870 °C
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262:crystalline structure. It is named after German
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515:Baumeister, Avallone, Baumeister (1978). "6".
547:: CS1 maint: multiple names: authors list (
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309:elements. As a result of the quenching, the
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344:reaches the martensite start temperature (M
313:austenite transforms to a highly strained
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564:Steel Metallurgy for the Non-Metallurgist
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27:Type of steel crystalline structure
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340:begins during cooling when the
317:form called martensite that is
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239:Martensite in AISI 4140 steel
32:Diffusionless transformations
271:diffusionless transformation
30:For the transformation, see
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562:Verhoeven, John D. (2007).
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392:and in special steels like
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390:yttria-stabilized zirconia
193:Other iron-based materials
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523:. McGraw Hill. pp.
315:body-centered tetragonal
281:Martensite is formed in
129:Widmanstätten structures
592:Engineering Materials 2
616:Bhadeshia, H. K. D. H.
285:by the rapid cooling (
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620:Geometry of Crystals
497:(March 1972) , "3",
311:face-centered cubic
124:Tempered martensite
495:Khan, Abdul Qadeer
329:steel is 400
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682:Ceramic materials
588:Ashby, Michael F.
401:activation energy
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226:Wrought iron
216:Ductile iron
155:Spring steel
150:Carbon steel
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394:TRIP steels
375:In certain
160:Alloy steel
104:Spheroidite
18:Martensitic
676:Categories
474:References
468:Tool steel
277:Properties
254:is a very
252:Martensite
211:White iron
185:Tool steel
119:Ledeburite
81:Martensite
618:(2001) .
543:cite book
448:Eutectoid
422:tempering
405:cryogenic
357:eutectoid
342:austenite
327:pearlitic
299:cementite
291:austenite
289:) of the
287:quenching
206:Gray iron
201:Cast iron
76:Cementite
71:Austenite
443:Eutectic
437:See also
426:tungsten
338:reaction
307:alloying
293:form of
258:form of
109:Pearlite
86:Graphite
431:brittle
331:Brinell
137:Classes
114:Bainite
66:Ferrite
687:Steels
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527:, 18.
355:For a
323:carbon
57:Phases
41:Steels
321:with
260:steel
624:ISBN
596:ISBN
568:ISBN
549:link
529:ISBN
365:lath
295:iron
256:hard
301:(Fe
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