Southwest Indian Craft Arts. Clara Lee Tanner. University of Arizona Press, Tucson, 1968. 206 pp., illus. $15

Judd, Neil M.

doi:10.1126/science.163.3871.1053

Cited by 4 publications

(10 citation statements)

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“…[3] A separate kinetic model is used for the ferrite region that surrounds the pearlite. The diffusion-limited model for the austenitization of ferrite is very similar to others (Oddy et al, [15] Judd and Paxton, [5] and Molinder [4] ). The differences between the current model and the earlier models will be discussed after our model is presented.…”

Section: B Austenitization Kineticsmentioning

confidence: 86%

“…[1] through [6] is similar to that developed by others. Judd and Paxton [5] and Molinder [4] used similar expressions for the diffusional decomposition of the ferrite. However, both studies limited the model to temperatures below the A e3 line.…”

Section: B Austenitization Kineticsmentioning

confidence: 97%

“…For these models to be applicable, they must describe the phase transformation kinetics associated with both the on-heating and on-cooling transformations, and these descriptions must be experimentally validated. In general, the formation of austenite in steels has received less attention than the decomposition of austenite, although there have been a number of experimental [1][2][3][4][5][6] and numerical studies [7][8][9][10][11][12] of the process. These studies have yielded significant insight into the transformation from both mechanistic and computational perspectives, but there are some limitations and difficulties in applying this insight to large scale process modeling.…”

Section: Introductionmentioning

confidence: 99%

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A method for extracting phase change kinetics from dilatation for multistep transformations: Austenitization of a low carbon steel

Dykhuizen

Robino

Knorovsky

1999

Metall Mater Trans B

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This article describes the development of a method for determining phase change kinetics for multistep diffusion limited solid-state transformations from dilatation data. Since each step in a multistep reaction proceeds at a different rate, and the volume changes for the transformations are, in general, not equal, determination of the reaction kinetics from the dilatation data is not straightforward. Thus, a model is developed for the phase change process in which the transient dilatation is calculated based on the fractional extent of the various phases present. In this way, kinetic parameters are determined that allow the best match to the experimental data. However, both random and systematic experimental errors make reproduction of the experimental dilatation difficult. Therefore, a selfcalibration process is developed that uses portions of the dilatation data to obtain the density variation of the various phases with temperature to help correct for experimental uncertainties. This procedure also enables the model to be used in situations where accurate property data are not available. The model and procedures are applied to the formation of austenite in a pearlite/ferrite low carbon steel where the pearlite and ferrite regions transform at different rates. A single kinetic parameter set allows reproduction of transformation transients of significantly different heating rates. These parameters can then be used to describe the austenitization for any time-temperature path. Excellent agreement between the model and experimental data is shown.

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Section: B Austenitization Kineticsmentioning

confidence: 86%

Section: B Austenitization Kineticsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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A method for extracting phase change kinetics from dilatation for multistep transformations: Austenitization of a low carbon steel

Dykhuizen

Robino

Knorovsky

1999

Metall Mater Trans B

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“…Long-range diffusion of carbon has been shown to be the rate controlling mechanism during austenitization of spheroidized ferrite-carbide aggregates. [10] In this case, isolated spherical carbide particles, several micrometers in diameter, act as the source of carbon as an austenite/ferrite interface proceeds outward from the carbide while the austenite/carbide interface proceeds inward until there is no carbide remaining. In a plain carbon eutectoid steel, there are extensive nucleation sites for austenite in lamellar eutectoid colonies due to the large number of ferrite/cementite boundaries in these regions.…”

Section: Introductionmentioning

confidence: 99%

“…These include experimental studies on the influence of starting microstructures on the transformation kinetics, [7][8][9][10] dilatometry, [9,11,12] and modeling of the transformation during continuous heating at varying scales of complexity. [13][14][15][16] As a result of these studies, there is some understanding of the austenite nucleation and growth process under limited conditions.…”

Section: Introductionmentioning

confidence: 99%

A Study of Diffusion- and Interface-Controlled Migration of the Austenite/Ferrite Front during Austenitization of a Case-Hardenable Alloy Steel

Schmidt

Damm

Sridhar

2007

Metall Mater Trans A

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Migrating austenite/ferrite interfaces in the ferrite regions of an alloy steel, containing 0.20 wt pct C, 0.87 wt pct Mn, and 0.57 wt pct Cr, with a ferrite/pearlite microstructure have been observed during austenitization by a high-temperature confocal scanning laser microscope in order to determine the mechanisms of transformation. The samples were subjected to isothermal (790°C to 850°C) and nonisothermal (0.5°C to 20°C/s) temperature profiles. The kinetic rates extracted from the observations were compared to models for long-range diffusion-controlled and interface reaction-controlled migration. The transition between the two mechanisms was found to occur at T 0 , which defines the temperature and composition at which a partitionless phase transformation is possible. Occurrence of the partitionless, interface-controlled transformation was confirmed by an analysis of carbon distribution and microstructure before and after a sample was subjected to a particular thermal profile. The mobility of such interfaces was found to be in the range 1.6AE10 )13 to 2AE10 )12 m 4 AEJ )1 AEs )1 , which is consistent with previous studies on interface-controlled migration of the reverse reaction, a to c, during cooling of dilute substitutional iron alloys. The diffusioncontrolled migration, at temperatures below T 0 , was found to occur in two stages: an initial stage, at which the growth rate can be predicted by a semi-infinite diffusion model; and a second stage, at which the growth slows more rapidly, possibly due to the overlap of diffusion fields.

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Laser transformation hardening of tempered 4340 steel

Shiue

Chen

1992

Metall Trans A

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A CO2 laser with a fixed laser power of 1.8 KW was employed to harden the surface of some AISI 4340 steel specimens, with a scan rate from 5 to 10 mm/s. The influence of scan rates and tempering treatments of the alloy on the hardness profile and microstructure of the laserhardened zone was analyzed. Microstructures in the hardened zone consisted of mainly lath and twinned martensites. However, depending on the scan rate, autotempered martensite has also been found. In the transition zone of laser-treated specimens, partially dissolved carbides with austenite envelopes and/or austenite islands in a matrix of martensite were observed. The time required for complete carbide dissolution into austenite during laser treatment depended on the tempering conditions. A lower tempering temperature of the alloy produced a deeper hardened zone and a narrower transition zone in the hardness profile. A simple mathematical estimation of the hardness profile, based on the carbon diffusion distance in austenite, was performed. The calculated results are in reasonably good agreement with the measured hardness profiles and the microstructural observations in the laser transformation hardening process.

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Southwest Indian Craft Arts. Clara Lee Tanner. University of Arizona Press, Tucson, 1968. 206 pp., illus. $15

Cited by 4 publications

References 0 publications

A method for extracting phase change kinetics from dilatation for multistep transformations: Austenitization of a low carbon steel

A method for extracting phase change kinetics from dilatation for multistep transformations: Austenitization of a low carbon steel

A Study of Diffusion- and Interface-Controlled Migration of the Austenite/Ferrite Front during Austenitization of a Case-Hardenable Alloy Steel

Laser transformation hardening of tempered 4340 steel

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