Precipitation Sequence and Kinetics in an Fe-Si-Ti Alloy

Abstract:

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The Fe-Si-Ti system is known to show nanoscale precipitation of the Fe2SiTi Heusler phase with potentially high volume fraction (~4%), very high density and a size ranging from 1 to 20nm after artificial aging. The strong hardening potential of these precipitates make these steels candidates for automotive applications; however no understanding of the precipitation sequence (competition with other phases) nor the precipitation kinetics are available. The present study presents a quantitative study of the precipitation kinetics (size, volume fraction and number density) in a wide temperature range (450-800°C), realised by coupling systematically Small Angle Neutron Scattering (SANS), Transmission Electron microscopy (TEM) and Tomographic Atom Probe (TAP). Tensile tests were also carried out so as to determine the microstructure/properties relationships. Along the complete temperature range, it is shown that a compromise between time for precipitation and small precipitate sizes can be reached around 550°C. At this intermediate temperature, precipitation is shown to occur in two steps, linked with a second nucleation process after nucleation & growth of the first family of Fe2SiTi has been completed. This second precipitation step results in a temporary decrease in precipitate size and an increase in hardness. The nature of these precipitates is discussed in view of the TEM and TAP observations.

Info:

Periodical:

Solid State Phenomena (Volumes 172-174)

Edited by:

Yves Bréchet, Emmanuel Clouet, Alexis Deschamps, Alphonse Finel and Frédéric Soisson

Pages:

833-838

DOI:

10.4028/www.scientific.net/SSP.172-174.833

Citation:

M. Perrier et al., "Precipitation Sequence and Kinetics in an Fe-Si-Ti Alloy", Solid State Phenomena, Vols. 172-174, pp. 833-838, 2011

Online since:

June 2011

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Price:

$35.00

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