Isothermal martensite formation at sub-zero temperatures

Allan Stojko (Invited author), Mikkel Fougt Hansen (Invited author), Jan Slycke (Invited author), Marcel A. J. Somers (Invited author)

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Abstract

Sub-zero treatment of steels with an Mf below zero degrees Celsius relies (partly) on a continuation of the martensite formation. The present work reports on the observation of isothermal martensite formation in the sub-zero temperature regime for two steels: AISI 1070 and AISI 52100. Samples were austenitized and quenched in oil and thereafter investigated with vibrating sample agnetometry, which allows a quantitative assessment of the fraction of retained austenite as a function of the subzero temperature and time. Isothermal martensite formation was observed on interrupting the continuous cooling (5 K/min) with vibrating sample magnetometry at several temperatures in the range 80-233 K. The kinetics of isothermal martensite formation depends strongly on the temperature. Similar isothermal experiments with dilatometry indicated the occurrence of volume increase on isothermal holding, consistent with a continuation of the martensitic transformation. On prolonged isothermal holding a volume reduction was observed for AISI 52100, but not for AISI 1070. A mechanism is proposed that explains the occurrence of isothermal martensite formation.
Original languageEnglish
Title of host publication18. IFHTSE congress
Publication date2010
Publication statusPublished - 2010
EventInternational Federation for Heat Treatment and Surface Engineering - Rio de Janeiro, RJ, Brazil.
Duration: 1 Jan 2010 → …

Conference

ConferenceInternational Federation for Heat Treatment and Surface Engineering
CityRio de Janeiro, RJ, Brazil.
Period01/01/2010 → …
SeriesANAIS / Proceedings
ISSN1516-392x

Keywords

  • Sub-zero treatment
  • Magnetometry
  • Isothermal martensite
  • Dilatometry

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