GRADUATE STUDENT RESEARCH HIGHLIGHTS
2015 Spring Seminar Series
Friday, January 23, 2015
307 SERF Building
2:00 – 2:15
Adam Lindsey
(Zhuravleva’s Research Group)
Dept. of Materials Science & Engineering
The Development of a Cost Effective Multi-Ampoule
Growth Station for Large Volume Bulk Production
of Metal Halide Scintillator Crystals
A significant portion of the cost of synthesizing bulk
single crystals of metal halide scintillators can be
attributed to the cost of the equipment in a typical
Bridgman growth station comprised of a multi-zone
furnace and translation components. In an effort to
reduce these costs, the Multi-Ampoule Growth Station
(MAGS) has been developed as a prototype to
investigate the effectiveness of simultaneous growth of
multiple crystals in a singular growth station. This
experimental test bed was developed to minimize the
cost of the furnace construction while exploring the
advantages and potential challenges to growth of high
quality crystals using multiple ampoule bays. The goal
with this technology is to develop control,
reproducibility, and maintainability of the growth
station while maintaining an overall reduction in the
equipment cost over conventional Bridgman furnace
design. The objective of this research is to investigate
the capability of this cost effective solution to the
advanced manufacturing processes specifically required
by single crystal synthesis of the metal halide class of
materials.
2:20 – 2:35
Bilin Chen
(Liaw’s Research Group)
Dept. of Materials Science & Engineering
Studying the Deformation Behavior of an
X52 Pipeline Steel by Neutron-Diffraction
Measurements
In-situ neutron-diffraction experiments were
performed to study the deformation behavior
around the crack tip of an X52 [Fe-0.071C1.06Mn-0.24Si-0.026Nb, weight percent (wt. %)]
pipeline
steel
sample,
using
the VULCAN Engineering
Diffractometer
at
Spallation Neutron Source (SNS), Oak Ridge
National Laboratory (ORNL). Compact-tension
(CT) specimen was employed in the study.
Samples were precracked to a certain crack length,
and then they were divided into two groups. One
group was hydrogen-charged in a high pressure
hydrogen atmosphere, the other served as
reference. Both samples were tested to detect the
influence of hydrogen. Figures of Lattice
parameter versus distance from the crack tip was
plotted at various load levels during one fatigue
(loading-unloading) cycle. It was shown that
lattice parameters were expanded because of the
presence of hydrogen, while they were expanded
differently with locations and load levels.
Join us for refreshments at
1:30 in 307 SERF
2:40 – 2:55
Haoyan Diao
(Liaw’s Research Group)
Dept. of Materials Science & Engineering
Mechanical properties of 3 most-studied highentropy alloys (HEAs)
High-entropy alloys (HEAs), a new class of materials,
are equiatomic, multi-element systems that can
crystallize as a single phase, despite containing
multiple elements with different crystal structures. In
this talk, I will review the mechanical properties of 3
representative and most-studied HEAs, CoCrFeMnNi,
AlxCoCrCuFeNi, and refractory HEAs. The
CoCrFeMnNi is confirmed to be consisted of a
single face-centered cubic (FCC) solid-solution
phase which solidifies dendritically. The elastic
behavior studied by neutron diffraction, plastic
behavior studied by tensile tests, and fracture
toughness at low temperature are summarized to
reveal the deformation mechanism of HEAs. The
aluminum ratio effect on the structure type
transition
and
fatigue
properties
of
AlxCoCrCuFeNi are presented. The hightemperature mechanical properties of refractory
HEAs are presented and compared with
conventional alloys. All in all, even though the
mechnical properties of HEAs scatter in a wide
range, many properties are still promising.