skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Isothermal Nature of Martensite Formation in Pt-Modified beta-NiAl Alloys


No abstract prepared.

; ; ; ; ;
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
Report Number(s):
IS-J 7204
Journal ID: ISSN 1359-6454; ACMAFD; TRN: US200722%%1236
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Materialia
Country of Publication:
United States

Citation Formats

D.J. Sordelet, M.F. Besser, R.T. Ott, B.J. Zimmerman, W.D. Porter, and B. Gleeson. Isothermal Nature of Martensite Formation in Pt-Modified beta-NiAl Alloys. United States: N. p., 2007. Web. doi:10.1016/j.actamat.2006.11.038.
D.J. Sordelet, M.F. Besser, R.T. Ott, B.J. Zimmerman, W.D. Porter, & B. Gleeson. Isothermal Nature of Martensite Formation in Pt-Modified beta-NiAl Alloys. United States. doi:10.1016/j.actamat.2006.11.038.
D.J. Sordelet, M.F. Besser, R.T. Ott, B.J. Zimmerman, W.D. Porter, and B. Gleeson. Tue . "Isothermal Nature of Martensite Formation in Pt-Modified beta-NiAl Alloys". United States. doi:10.1016/j.actamat.2006.11.038.
title = {Isothermal Nature of Martensite Formation in Pt-Modified beta-NiAl Alloys},
author = {D.J. Sordelet and M.F. Besser and R.T. Ott and B.J. Zimmerman and W.D. Porter and B. Gleeson},
abstractNote = {No abstract prepared.},
doi = {10.1016/j.actamat.2006.11.038},
journal = {Acta Materialia},
number = ,
volume = ,
place = {United States},
year = {Tue Jan 30 00:00:00 EST 2007},
month = {Tue Jan 30 00:00:00 EST 2007}
  • Oxide growth stresses were measured in situ at 1100 C on commercial Pt-modified NiAl and NiCoCrAlY bond coat alloys using synchrotron X-rays. Measurements were taken on samples that had no preoxidation, as well as on samples that had experienced 24 one-hour thermal exposures at 1150 C, a condition known to induce rumpling in the Pt-modified NiAl alloy, but not in the NiCoCrAlY alloy. The NiCoCrAlY alloy showed continuous stress relaxation under all conditions, whereas the Pt-modified NiAl alloys would typically stabilize at a fixed (often non-zero) stress suggesting a higher creep strength in the 'Thermally Grown Oxide' on the lattermore » alloy, though the precise behavior was dependent on initial surface preparation. The formation of martensite in the Pt-modified NiAl alloys was also observed upon cooling and occurred at temperatures below 200 C for all of the samples observed. Based on existing models, this M{sub s} temperature is too low to account for the rumpling observed in these alloys.« less
  • The experimental information on isothermal {alpha} martensite in ferrous alloys is reviewed. From the kinetics one can clearly distinguish between three groups of alloys yielding isothermal martensite. The first group contains high alloy steels with a low M{sub s} temperature. They form isothermal martensite with a temperature dependence corresponding to a very low activation energy, possibly 7 kJ/mol. The second group contains steels with an appreciable amount of carbon. Its rate of formation of isothermal martensite can be explained by assuming that it is triggered by submicroscopic plates of bainite formed with a rate controlled by carbon diffusion. The thirdmore » group contains Fe-Ni alloys with up to about 25% Ni. There the temperature dependence corresponds to an activation energy of about 80 kJ/mol. It is proposed that their transformation is related to the transformation causing plateau II in experiments with very rapid cooling a transformation which has previously been proposed to be related to the formation of bainite.« less
  • The present paper is concerned with the nature of the martensite, which provides the basis for the maraging treatment. Rather than forming martensite during cooling, 1RK91 develops martensite when held at a constant temperature in a range from room temperature and below. Isothermal martensite formation showing C-curve kinetics was found to occur in the maraging steel 1RK91, the nose temperature being about {minus}40 C. The kinetics was found to be enhanced for higher austenitizing treatment temperatures, presumably through a combination of larger grain size and a larger number of quenched in nuclei for isothermal martensite transformation. Experiments involving different coolingmore » rates showed that fast cooling enhanced the transformation kinetics. Based on this observation it is suggested that quenched-in vacancy clusters provide suitable strain embryos for isothermal martensite nucleation.« less
  • Molybdenum oxycarbide formed from oxidized Mo{sub 2}C or reduced MoO{sub 3} is an active and very selective catalyst for the isomerization of n-heptane compared to supported Pt. Deactivation experiments performed on the catalysts with different concentrations of organosulfur compounds show that molybdenum oxycarbide exhibits a very high resistance to deactivation, whereas with platinum-based catalysts deactivation occurs even at low sulfur concentration in the feed. Deactivation can be slowed by increasing the hydrogen partial pressure from 6 to 20 bar. In these conditions, the molybdenum oxycarbide shows no deactivation with sulfur concentrations up to 120 ppm of S. In addition, themore » deactivated molybdenum catalysts can be easily regenerated by mild oxidative treatment under flowing air at atmospheric pressure and 723 K for 2 h followed by a reactivation period under the hydrogen and hydrocarbon mixture.« less