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time-temperature transformation

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Series: ASM Technical Books
Publisher: ASM International
Published: 01 March 2006
DOI: 10.31399/asm.tb.pht2.t51440009
EISBN: 978-1-62708-262-4
... on transformations and on the classification of steels by carbon content. The chapter ends with a discussion on the effect of time on transformation and on the use of time-temperature-transformation diagrams. allotropy austenite-to-ferrite transformation carbon content commercially pure iron...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 March 2012
DOI: 10.31399/asm.tb.pdub.t53420303
EISBN: 978-1-62708-310-2
... Abstract This chapter examines two important strengthening mechanisms, martensitic and bainitic transformations, both of which occur under nonequilibrium cooling conditions. It explains how time-temperature-transformation diagrams are constructed and how they are used to understand and control...
Series: ASM Technical Books
Publisher: ASM International
Published: 31 December 2020
DOI: 10.31399/asm.tb.phtbp.t59310055
EISBN: 978-1-62708-326-3
... transformation (CCT) diagram (shaded) and isothermal transformation diagram of a carbon steel with a eutectoid composition. Source: Ref 1 Isothermal transformation diagrams, also referred to as time-temperature transformation (TTT) diagrams, are used to describe either the...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 March 2012
DOI: 10.31399/asm.tb.pdub.t53420143
EISBN: 978-1-62708-310-2
... ] where k 0 is a constant, Q is the activation energy, R is the universal gas constant, and T is the temperature. Thus, the growth rate is very dependent on temperature, particle shape, and time. Figure 8.17 illustrates this with a time-temperature-transformation (TTT) diagram showing the time...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 March 2012
DOI: 10.31399/asm.tb.pdub.t53420015
EISBN: 978-1-62708-310-2
..., many particles will form where the growth rate is lower, and the resulting transformation product will be much finer. Fig. 2.15 Transformation rate as a function of temperature. Source: Ref 2.4 as published in Ref 2.2 The rate of transformation and the time required for the...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 November 2011
DOI: 10.31399/asm.tb.jub.t53290099
EISBN: 978-1-62708-306-5
... will be a function of both the surface power density and the time. Figure 5.1 shows how this temperature will vary on steel with power densities that range from 400 to 8000 W/cm 2 . At the lower value, it takes 2 min to melt the surface. If that heat source were a point on the flat surface, then the...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 November 2007
DOI: 10.31399/asm.tb.smnm.t52140083
EISBN: 978-1-62708-264-8
... eventually begin to transform to one of the three product constituents. Consider a pearlite steel, such as steel A in Fig. 9.2 . After the sample has been quenched to the temperature labeled T nose for the time labeled “1” on the IT diagram at the left, the austenite will start to form pearlite. This...
Series: ASM Technical Books
Publisher: ASM International
Published: 31 December 2020
DOI: 10.31399/asm.tb.phtbp.t59310163
EISBN: 978-1-62708-326-3
... or soaking for several minutes after the steel has reached the proper austenitizing temperature throughout its cross section. Very coarse cementite or alloy carbides require longer times to dissolve and diffuse into the austenite. Total heating time for a specific thickness is a function of the...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 November 2013
DOI: 10.31399/asm.tb.mfub.t53740271
EISBN: 978-1-62708-308-9
.... At rapid cooling rates, it is necessary to use a time-temperature-transformation (TTT) diagram (also called an isothermal transformation, or IT, diagram). The TTT diagrams are so named because they depict transformations as a function of time and temperature. A fully developed TTT curve with the...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 May 2018
DOI: 10.31399/asm.tb.hma.t59250059
EISBN: 978-1-62708-287-7
... ( FIG. 5.4 ). They showed for the first time that the transformation to hard martensite did not occur until the steel being quenched had cooled to temperatures well below that where the two-phase microstructure of pearlite formed. A few years later (1922), American metallurgist W.R. Chapin showed that...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 March 2012
DOI: 10.31399/asm.tb.pdub.t53420239
EISBN: 978-1-62708-310-2
... time are then analyzed for deviations from the smooth curve found for materials undergoing no phase changes ( Fig. 12.1 ). Fig. 12.1 Ideal cooling curve with no phase change. Source: Ref 12.1 When a pure element is cooled through its freezing temperature, its temperature is maintained...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 September 2008
DOI: 10.31399/asm.tb.fahtsc.t51130255
EISBN: 978-1-62708-284-6
..., ferrite, and cementite. The formation of these products and the proportions of each are dependent on the time and temperature cooling history of the particular alloy and the elemental composition of that alloy. The transformation products formed are typically illustrated with the use of transformation...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 September 2008
DOI: 10.31399/asm.tb.fahtsc.t51130001
EISBN: 978-1-62708-284-6
... temperature. Dimensional changes are possible, depending on the carbon content and microstructural transformation product formed. The volume change (%) is [4.64–0.53 (%C)] for the reaction from austenite to martensite. The two most commonly used transformation diagrams are time-temperature transformation...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 September 2008
DOI: 10.31399/asm.tb.fahtsc.t51130285
EISBN: 978-1-62708-284-6
... ratio. At that time, all the experiments were performed at room temperature, because no one anticipated that temperature may also have an effect on the results. The effect of test temperature received attention in the beginning of 1944, when Jolivet and Vidal introduced experiments at different...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 November 2007
DOI: 10.31399/asm.tb.smnm.t52140117
EISBN: 978-1-62708-264-8
... finish temperature, M f .) Fig. 12.1 Cooling curve at the surface and center of a rapidly quenched bar of 5140 steel superimposed on the continuous transformation curve There was a considerable amount of research done on water and oil quenching at approximately the time period when...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 November 2007
DOI: 10.31399/asm.tb.smnm.t52140071
EISBN: 978-1-62708-264-8
... 360 1 250 Coarse 2 180 3 125 4 90 Medium 5 65 6 45 7 32 Fine 8 22 9 16 10 11 Very fine 11 8.0 12 5.6 13 4.0 Ultrafine 14 2.8 15 2.0 As austenite is heated to higher temperatures or held for longer times at temperature...
Series: ASM Technical Books
Publisher: ASM International
Published: 31 December 2020
DOI: 10.31399/asm.tb.phtbp.t59310029
EISBN: 978-1-62708-326-3
... , meaning that sufficient time is needed for the metal to reach equilibrium for a given phase change. Enough energy, referred to as latent heat, must be added or released to complete an equilibrium transformation. Experimental latent-heat values at the transformation temperatures of pure iron are given in...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 November 2007
DOI: 10.31399/asm.tb.smnm.t52140021
EISBN: 978-1-62708-264-8
... cementite plates of its pearlite are transformed completely into austenite in progressively shorter time frames as the temperature is raised. Because the method requires particles of cementite to be present in the cooling austenite, hypoeutectoid steels cannot be held for very long above the A 1...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2001
DOI: 10.31399/asm.tb.aub.t61170417
EISBN: 978-1-62708-297-6
... reduce ductility and creep strength. Zirconium is a weak beta stabilizer, but does retard the rates of transformation. Molybdenum is an important beta stabilizer that promotes hardenability and short-time elevated-temperature strength. Molybdenum makes welding more difficult and reduces long-term...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 March 2012
DOI: 10.31399/asm.tb.pdub.t53420117
EISBN: 978-1-62708-310-2
... driving force is zero at the peritectic temperature. The time dependence is pronounced for the peritectic transformation. Therefore, the amount of β phase formed will depend on the cooling rate or on holding time if isothermal conditions are established. Localized nucleation of β and shape changes of...