Expertise
Materials processing, amorphous alloys, advanced materials.
Field
of Study
Our group makes fundamental studies of materials far from equilibrium.
This includes synthesis, processing, and characterization of such materials.
Materials of particular interest include:
- Amorphous
and Glassy Metallic Materials
- Nanocrystalline
Materials
- Metallic
Glass Matrix Composites
Past work
has included studies of the crystal to glass transformations, mechanically
alloys nanophase materials, ion solid interactions, and materials processing
by rapid solidification methods.
Recent work focuses on the study of "bulk" metallic glass forming alloys.
We have developed several families of metallic alloys which exhibit unusual
ability to form glass. These materials can be cast as monolithic glass
samples. We carry out research on the glass forming liquids. Studies of
viscosity, flow, atomic diffusion, surface tension, and crystal nucleation
in the undercooled melt are carried out. Fundamental studies of the glass
transition and thermal properties of the liquid and glassy phases are
done.
Characterization techniques employed include x-ray diffraction and small
angle x-ray scattering, neutron scattering (in collaboration with IPNS,
at Argonne Nat. Lab), field ion microscopy, high resolution TEM, thermal
analysis and calorimetry, containerless processing by electromagnetic
and electrostatic levitation of liquids. We have carried out flight experiments
on liquid alloys aboard the IML-2 and MSL-1 flights of the space shuttle.
The mechanical properties of the monolithic glasses are under investigation.
These include measurements of strength, ductility, toughness, and quasi
static and dynamic deformation behavior. Collaborative research with faculty
in the Applied Mechanics option (e.g. Prof. A.J. Rosakis) is part of this
work. Studies of deformation and failure as a function of strain rate
are done using high speed imaging and temperature measurement methods.
Metallic glass matrix composites have been synthesized in which ceramic
reinforcement or ductile metal reinforcement is used to strengthen, toughen,
and otherwise improve the engineering properties of metallic glasses.
The work includes studies of impact, fatigue, and other important engineering
properties of the composites.
Development of casting and processing methods for producing near net shape
components of metallic glass is carried out. Methods for synthesis of
composite materials are explored. The program has a strong emphasis on
applications and technology transfer.
Selected
Publications
Choi-Yim H, Conner RD, Szuecs F, et al., "Processing, Microstructure
and Properties of Ductile Metal Particulate Reinforced Zr57Nb5Al10CU15.4Ni12.6
bulk Metallic Glass Composites", ACTA MATER 50 (10): 2737-2745
JUN 12 2002
Schroers J, Johnson WL, "Extremely Low Critical Cooling Rate for
Pd43Ni10Cu27P20", MATER SCI FORUM 386-3: 111-115 2002
Schroers J, Wu Y, Johnson WL, "Heterogeneous Influences on the
Crystallization of Pd43Ni10Cu27P20", PHILOS MAG A 82 (6): 1207-1217
APR 2002
Schroers J, Johnson WL, "Extremely Low Critical Cooling Rate Measured
on Dispersed Pd43Ni10Cu27P20", APPL PHYS LETT 80 (12): 2069-2071
MAR 25 2002
Johnson WL, "Bulk Amorphous Metal - An Emerging Engineering Material"
JOM-J MIN MET MAT S 54 (3): 40-43 MAR 2002
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