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Topic: Martensite

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	Martensite -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-20)
		Martensite has a very similar crystalline structure to (A solid solution of ferric carbide or carbon in iron; cools to form pearlite or martensite) austenite, and identical chemical composition.
		Martensite has a lower density than ferrite, so that the transformation between phases often results in a relative change of volume: this can be seen vividly in the Japanese (additional info and facts about Katana) Katana, which is straight before (The act of extinguishing; causing to stop burning) quenching.
		The difference between austenite and martensite is, in some ways, quite small: while the average unit cell of austenite is, on average, a perfect little cube, the transformation to martensite sees this cube distorted, so that it's a tiny bit longer than before in one dimension and a little bit shorter in the other two.
	www.absoluteastronomy.com /encyclopedia/m/ma/martensite.htm (582 words)

	Encyclopedia: Martensite (Site not responding. Last check: 2007-10-20)
		Martensite has a lower density than ferrite, so that the transformation between phases often results in a relative change of volume: this can be seen vividly in the Japanese Katana, which is straight before quenching.
		Because phases such as ferrite, cementite, and austenite are more chemically stable at any composition and temperature, martensite is not in thermodynamic equilibrium; for this reason, martensite is not shown in the equilibrium phase diagram of the iron-carbon system.
		Martensite can be seen as an interim structure that the material takes on until a stable state can be reached; this phenomenon is known as metastability.
	www.nationmaster.com /encyclopedia/Martensite (1333 words)

	Cover Story: Microstructure of Ferrous Alloys (Site not responding. Last check: 2007-10-20)
		Martensite is a phase when formed by quenching but becomes a constituent after tempering as in decomposes from body centered tetragonal (bct) martensite to body centered cubic (bcc) ferrite and cementite.
		These martensite start and end temperatures are depressed to such an extent that the austenite is not fully converted to martensite during quenching and the remaining austenite, called retained austenite, is present (but not necessarily stable) at room temperature.
		Martensite is a generic term for the body-centered tetragonal phase that forms by diffusionless transformation, and the parent and product phases have the same composition and a specific crystallographic relationship.
	www.industrialheating.com /CDA/ArticleInformation/coverstory/BNPCoverStoryItem/0,2830,17985,00.html (3469 words)

	The Tempering of Martensite: Part One (Site not responding. Last check: 2007-10-20)
		Martensite is a highly supersaturated solid solution of carbon in iron, which, during tempering, rejects carbon in the form of finely divided carbide phases.
		Essentially, martensite is a highly supersaturated solid solution of carbon in iron, which, during tempering, rejects carbon in the form of finely divided carbide phases.
		Martensite formed in medium and high carbon steels (0.3-1.5% C) is not stable at room temperature because interstitial carbon atoms can diffuse in the tetragonal martensite lattice at this temperature.
	www.key-to-steel.com /ViewArticle.asp?ID=127 (1200 words)

	Tempered Martensite
		Given that carbon is able to migrate in martensite even at ambient temperature, it is likely that some of it redistributes, for example by migrating to defects, or by rearranging in the lattice such that the overall free energy is minimised.
		Martensite is said to be supersaturated with carbon when the concentration exceeds its equilibrium solubility with respect to another phase.
		Figure: (a) Martensite (α') is hindered by austenite grain boundaries whereas allotriomorphic ferrite (α) is not.
	www.msm.cam.ac.uk /phase-trans/2004/Tempered.Martensite/tempered.martensite.html (3808 words)

	June 2003 JMR
		The relationship between the nanohardness and the microstructures in the Fe-C martensite was studied to understand the contributions of the matrix and the grain boundary to the macroscopic strength.
		As-quenched martensite was examined for five kinds of Fe-C alloys with various carbon contents in the range of 0.1-0.8 mass%, while quench-tempered martensite was investigated for an Fe-0.4% C alloy.
		For the quench-tempered specimens, a significant reduction of the grain boundary effect occured at the tempering temperature of 723 K. It is mainly due to the depression of the locking parameter caused by the disappearance of the film-like carbides on the boundaries.
	www.mrs.org /publications/jmr/jmra/2003/jun/026.html (194 words)

	Untitled (Site not responding. Last check: 2007-10-20)
		Martensite structures do not form at a constant temperature, rather the austenite is converted to martensite as the steel cools to ambient temperature.
		These carbides upset the uniform structure of the martensite crystals, and are a significant factor in the brittleness of hardened and tempered steel.
		It is at this point that complete martensite transformation will have occured and the part may be allowed to return to ambient temperature at a rate which will minimize internal stresses.
	lennon.pub.csufresno.edu /~rlk16/cryo.html (1623 words)

	SQUIDs and MBN for NDT of Steel
		Detection and characterisation of small amounts of martensite in such steels is very useful for early detection of fatigue damage and hence for evaluation of in-service degradation [1].
		Since marteniste is a magnetic phase in a non-magnetic austenite matrix, it is possible to exploit the magnetic methods of NDE for characterisation of martensite.
		This difference in behaviour is attributed to the orientation relationship between the easy magnetisation direction, [100] of the martensite and the direction of the applied magnetic field.
	www.geocities.com /raobpc/SQUIDs.html (3149 words)

	Heat Treatments: Softening: Annealing
		This brittleness is caused by a predominance of Martensite.
		The prevalent Martensite is a somewhat unstable structure.
		When heated, the Carbon atoms diffuse from Martensite to form a carbide precipitate and the concurrent formation of Ferrite and Cementite, which is the stable form.
	www.efunda.com /processes/heat_treat/softening/tempering.cfm (474 words)

	Martensite (Site not responding. Last check: 2007-10-20)
		Named for the German metallurgist Adolph Martens, Martensite is the hardened microstructure of steel that is obtained by cooling Austenite fast enough to trap carbon atoms within the cubic iron matrix distorting it into a body centered tetragonal structure.
		The temperature at which martensite begins to form in an alloy is given the designation Ms (martensite start) the temperature at which martensite is done forming is Mf.
		Formation occurs in "packets", with lathe martensite, as the crystalline structure begins with single plane forming across the grain with many subsequent branches nucleating from the central one in a parallel "fern' or "feather" like configuration.
	www.cashenblades.com /Info/Martensite.htm (236 words)

	A Brief History of Martensites
		Owen, "Martensite", ASM International, 1992: "A History of Martensite: Some Thoughts on the Early Hardening of Iron" by R. Maddin, and "A History of Martensite: Early Ideas on the Structure of Steel", by C.
		By dissolving carbon into it, one stabilizes highly distorted martensitic domains leading to hard, brittle cast-iron; by tempering to draw out the carbon into precipitates, one then toughens the material making it resistant to cracks, forming steel.
		Martensite "needles" in a matrix of austenite in a high carbon steel.
	www.lassp.cornell.edu /sethna/Tweed/Martensite_History.html (753 words)

	Untitled Document (Site not responding. Last check: 2007-10-20)
		Martensite is the phase of shape memory alloys that occurs at lower temperatures.
		If the SMA is unstressed and heated from the martensitic phase, the transformation from martensite to austenite begins at the temperature As, the temperature at which the phase transformation begins, and continues to change until the material is completely austinite, which occurs at the temperature Af.
		The stress induced martensite mechanism is based upon the fact that the stress needed to form stress induced martensite is higher than the stress that the martensite reverts to austenite.
	www.uvm.edu /~swgordon/231-03/finprojects/Stephanie/sma2.htm (2912 words)

	CRYOGENIUS-Cryogenic Technical Article. (Site not responding. Last check: 2007-10-20)
		Peaks (211) of martensite and peaks (311) of the retained austenite were employed.
		It was seen that the (011) martensite plane is parallel to the (010) n-carbide plane, the (111) martensite direction is parallel to the (101) n-carbide direction.
		This existence of the lattice correspondence between two phases implies that (010) n-carbide plane is derived from (110) martensite plane, and (100), (010) and (001) n-carbide directions are derived from (110), (110) and (001) martensite directions respectively.
	www.cryogenius.co.za /Cryo_Tech_Article1.html (2192 words)

	Microstructure of ausformed lath martensite in 18%Ni maraging steel
		The microstructure of ausformed lath martensite in 18%Ni maraging steel was studied by analyzing electron backscatter diffraction pattern obtained by scanning electron microscopy and Kikuchi diffraction pattern obtained by transmission electron microscopy.
		In non-ausformed lath martensite structure, blocks and packets are clearly observed by optical microscopy.
		By ausforming of 60% at 773 K, packet and block widths of lath martensite decrease whereas the packet is elongated along rolling direction.
	www.edpsciences.org /articles/jp4/abs/2003/11/jp4pr10p453/jp4pr10p453.html (169 words)

	Engineering Materials – NOTES – Chapter 9 – Phase Diagrams (Site not responding. Last check: 2007-10-20)
		Martensite is the strongest and hardest phase in steel and is very important in the heat treatment and hardenability of steels.
		Note that rapid quenching to form martensite may crack a metal due to the internal stresses that are produced by the different transformation rates within the metal (the surface cools fast, producing martensite, while the interior cools more slowly).
		Martensite is a Body-Centered Tetragonal (BCT) structure (similar to BCC, except one side is longer than the other two sides).
	www.uwplatt.edu /~mirth/me3040ch10.htm (1320 words)

	Features Item: Understanding The Jominy End Quench Test (Site not responding. Last check: 2007-10-20)
		For example, the cooling rate at a distance of 10 mm (0.390 in.) from the quenched end is equivalent to the cooling rate at the center of an oil-quenched 28-mm (1.1 in.) diameter bar.
		The transformation from austenite to martensite may then be incomplete when the steel is quenched to room temperature, which leads to retained austenite.
		This composite microstructure of martensite and austenite results in a lower steel hardness, although the hardness of the martensite phase itself is still high (Fig.
	www.industrialheating.com /CDA/ArticleInformation/features/BNP__Features__Item/0,2832,62981,00.html (2011 words)

	Metal and Metallurgy engineering - Martensite content in 304SS
		As we know this martensite content can reduce the toughness strength of parent material and become more brittle that can be easily to crack in cryogenic temperature.
		This discusses the martensite transformation in some detail and gives equations (with references) for temperature induced and deformation induced martensite transformations as a function of composition.
		Martensite Content has been measured by using Induction Magnetic Technique.In the last measurement (June 2002) carried out by loading arm's manufacturer, ferrite content are 14% in welded area and 12% in the base material.
	www.eng-tips.com /viewthread.cfm?qid=41326 (1126 words)

	Steel - Open Encyclopedia (Site not responding. Last check: 2007-10-20)
		Cementite is a stochiometeric phase with the chemical formula of Fe Cementite often forms in regions of higher carbon content while other areas revert to ferrite around it, leading to a patterned layering known as perlite due to its pearl-like microscopic structure, or the similar but unpatterned bainite.
		Another important allotrope is martensite, a complex mixture of austenite and ferrite with about four to five times the strength of ferrite.
		Martinsite has a different unit cell structure than either ferrite or austenite and is produced by rapidly quenching austenite to room temperature.
	open-encyclopedia.com /Steel (2972 words)

	[No title]
		Martensite- very hard and very brittle steel and forms when steel is rapidly cooled from the austenite state.
		Bainite is formed which is the region of transformation between the rapid cooling curves for martensite and slower cooling pearlite.
		Structure is combination of bainite and tempered martensite.
	www.csuchico.edu /~jpgreene/itec104/m104_ch10-02_files/m104_ch10-02.ppt (762 words)

	ENGR 321: Homework Set 6
		At 25 C we have passed the Ms temperature, so we expect to see about 37% martensite (rough interpolation of 25 C between the Ms and Mf temperatures), with the rest metastable GAMMA.
		The highest strength component is the martensite, followed by the tempered martensite.
		a) 650 C for 1 sec: 100% martensite; 10 sec: 50% martensite, 50% pearlite; 1000 sec: 100% pearlite.
	oregonstate.edu /instruct/engr321/Homework/HomeworkW97/HW6.html (732 words)

	Heat Treatment of Steels — An Overview
		An appreciation of the thermal behaviour, with the accompanying microstructural changes, is fundamental to the understanding of heat treatment and the mechanical properties so generated.
		As is the austenite/ferrite transformation temperature and Ms is the martensite start transformation temperature.
		Martensite is a strong, hard, but brittle structure.
	www.azom.com /details.asp?ArticleID=314 (586 words)

	University of Wisconsin - Madison Internships in Public Science Education (IPSE) \| Quick Reference Activity Guide: ...
		In the martensite phase, the boundaries between regions with different orientations (the variants) appear to act as baffles for vibrations, resulting in a more muffled-sounding thud when martensitic samples are dropped
		In contrast, a rod that is in the low-temperature martensite phase at room temperature is comparatively flexible.
		The end of an austenitic rod will scratch the martensite, but a martensitic rod will not scratch the surface of the austenite.
	mrsec.wisc.edu /Edetc/IPSE/educators/memMetal.html (2081 words)

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