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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.
490:(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
American Society for Metals
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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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611:(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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583:(with corrections ed.). Oxford: Pergamon Press.
368:, martensite can be formed by working the steel at M
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0.35% carbon steel, water-quenched from 870 °C
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251:crystalline structure. It is named after German
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504:Baumeister, Avallone, Baumeister (1978). "6".
536:: CS1 maint: multiple names: authors list (
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298:elements. As a result of the quenching, the
404:Martensite is not shown in the equilibrium
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302:austenite transforms to a highly strained
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553:Steel Metallurgy for the Non-Metallurgist
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16:Type of steel crystalline structure
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329:begins during cooling when the
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228:Martensite in AISI 4140 steel
21:Diffusionless transformations
260:diffusionless transformation
19:For the transformation, see
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551:Verhoeven, John D. (2007).
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381:and in special steels like
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379:yttria-stabilized zirconia
182:Other iron-based materials
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512:. McGraw Hill. pp.
304:body-centered tetragonal
270:Martensite is formed in
118:Widmanstätten structures
581:Engineering Materials 2
605:Bhadeshia, H. K. D. H.
274:by the rapid cooling (
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609:Geometry of Crystals
486:(March 1972) , "3",
300:face-centered cubic
113:Tempered martensite
484:Khan, Abdul Qadeer
318:steel is 400
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671:Ceramic materials
577:Ashby, Michael F.
390:activation energy
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215:Wrought iron
205:Ductile iron
144:Spring steel
139:Carbon steel
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383:TRIP steels
364:In certain
149:Alloy steel
93:Spheroidite
665:Categories
463:References
457:Tool steel
266:Properties
243:is a very
241:Martensite
200:White iron
174:Tool steel
108:Ledeburite
70:Martensite
607:(2001) .
532:cite book
437:Eutectoid
411:tempering
394:cryogenic
346:eutectoid
331:austenite
316:pearlitic
288:cementite
280:austenite
278:) of the
276:quenching
195:Gray iron
190:Cast iron
65:Cementite
60:Austenite
432:Eutectic
426:See also
415:tungsten
327:reaction
296:alloying
282:form of
247:form of
98:Pearlite
75:Graphite
420:brittle
320:Brinell
126:Classes
103:Bainite
55:Ferrite
676:Steels
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516:, 18.
344:For a
312:carbon
46:Phases
30:Steels
310:with
249:steel
613:ISBN
585:ISBN
557:ISBN
538:link
518:ISBN
354:lath
284:iron
245:hard
290:(Fe
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