User Program study with D. Chandra, J. Smith, M. Coleman of University of Nevada Reno
| Researchers from
the Metallurgical Engineering Department at the University of Nevada,
Reno, visited HTML’s
Diffraction User Center to identify phase equilibria in zirconium iron
alloy
(SAES St198). This alloy consists mainly of Zr2Fe, with some Fe2Zr and
Zr.
These intermetallic phases have important applications for the
gettering
of hydrogen and tritium. However, the phase equilibria under different
atmospheres
had not been fully evaluated and understood. X-ray diffraction studies
were
undertaken using HTML's unique controlled atmosphere high temperature
X-ray
diffractometer, which enabled comparative studies under nitrogen,
hydrogen,
and inert atmospheres. Preliminary results under N2/H2 environment
indicate
that stable zirconium iron forms nitrides above 700°C. The Zr2Fe
phase
was actually a supercooled phase, and the equilibrium Zr3Fe phase was
obtained
after heating to 600°C. Heating the supercooled Zr2Fe phase
in
hydrogen environment showed that Zr3FeHx phase formed. Zr3FeH5.6
remained
stable between 300-400°C in pure hydrogen. Experiments in
96%N2-4%H2
gas mixtures showed that the Zr3FeH5.6 disproportionates to ZrN at
approximately
700°C. Thermal aging of Zr3FeH5.6 in 96%N2-4%H2 showed
disproportionation
to ZrN and α−Fe and others phases, yet to be determined. The HTML shared in two “best poster” awards for presentations describing User projects completed with UNR. The winning posters were: "High Temperature X-Ray Diffraction Studies During Hydriding of Zr2Fe" by J. Smith, D. Chandra, J.R. Wermer, and E.A. Payzant; and "Solid State Phase Transitions of NH4NO3-KNO3 Binary System" by W.-M. Chien, D. Chandra, J. Smith, NV, C.J. Rawn, and A.K. Helmy. |
||
|
|
|
|
| Instruments | Applications | Recent Projects | Publications
| Staff | Map
User Facility Access and
Proposal Form
Diffraction UC | Residual Stress UC | Thermophysical Properties UC
Diffraction & Thermophysical Prop. Group | High Temperature Materials Laboratory
Metals & Ceramics Division | Oak Ridge National Laboratory
Acknowledgments
URL: http://www.html.ornl.gov/duc/tisic.html