Understanding and Improving High-Temperature Structural Properties of Metal-Silicide Intermetallics Page: 2 of 143
This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
PROJECT SUMMARY
The objective of this project was to understand and improve high-temperature
structural properties of metal-silicide intermetallic alloys. Through research collaboration
between the research team at West Virginia University (WVU) and Dr. J.H. Schneibel at
Oak Ridge National Laboratory (ORNL), molybdenum silicide alloys were developed at
ORNL and evaluated at WVU through atomistic modeling analyses, thermo-mechanical
tests, and metallurgical studies. In this study, molybdenum-based alloys were ductilized
by dispersing MgAl204 or MgO spinel particles. The addition of spinel particles is
hypothesized to getter impurities such as oxygen and nitrogen from the alloy matrix with
the result of ductility improvement. The introduction of fine dispersions has also been
postulated to improve ductility by acting as a dislocation source or reducing dislocation
pile-ups at grain boundaries. The spinel particles, on the other hand, can also act as local
notches or crack initiation sites, which is detrimental to the alloy mechanical properties.
Optimization of material processing condition is important to develop the desirable
molybdenum alloys with sufficient room-temperature ductility. Atomistic analyses were
conducted to further understand the mechanism of ductility improvement of the
molybdenum alloys and the results showed that trace amount of residual oxygen may be
responsible for the brittle behavior of the as-cast Mo alloys.
For the alloys studied, uniaxial tensile tests were conducted at different loading
rates, and at room and elevated temperatures. Thermal cycling effect on the mechanical
properties was also studied. Tensile tests for specimens subjected to either ten or twenty
thermal cycles were conducted. For each test, a follow-up detailed fractography and
microstructural analysis were carried out. The test results were correlated to the size,
density, distribution of the spinel particles and processing time. Thermal expansion tests
were carried out using thermo-mechanical analyzer (TMA). Results showed that the
coefficient of thermal expansion (CTE) value decreases with the addition of spinel and
silicide particles. Thermo-cycling tests showed that molybdenum alloy with 6% wt of
spinel (MgAl204) developed microcracks which were caused by thermal expansion
mismatch between the spinel particles and molybdenum matrix, as well as the processing
conditions. Detailed post-mortem studies of microstructures and segregation of impurities
to the oxide dispersion/Mo interfaces were conducted using x-ray diffraction (XRD),
scanning electron microscpy (SEM), and energy dispersive spectroscopy (EDS).2
Upcoming Pages
Here’s what’s next.
Search Inside
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
Kang, Bruce S. Understanding and Improving High-Temperature Structural Properties of Metal-Silicide Intermetallics, report, October 10, 2005; United States. (https://digital.library.unt.edu/ark:/67531/metadc781526/m1/2/: accessed March 28, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.