NASA Scientific and Technical Aerospace Reports

Using an Atomic Force Microscope, we have examined the surface topographies associated with crevice coupons
representing the six classes of coupons of Titanium Grade 16 removed from Long-Term Corrosion testing after two years of
immersion. Only on coupons removed from Simulated Concentrated Well Water do we observe features which are likely to
represent embryonic pit formation. The coupons removed from the Simulated Acidified Well Water were too rough to yield
representative measurements.
NTIS
Titanium; Corrosion Tests; Cracks
20040070993 Lawrence Livermore National Lab., Livermore, CA
Characterization of Nanostructural Features in Irradiated Reactor Pressure Vessel Model Alloys
Wirth, B. D.; Odette, G. R.; Asoka-Kumar, P.; Howell, R. H.; Sterne, P. A.; Aug. 01, 2001; In English
Report No.(s): DE2003-15005550; UCRL-JC-145544; No Copyright; Avail: National Technical Information Service (NTIS)
Irradiation embrittlement in nuclear reactor pressure vessel steels results from the formation of a high number density of
nanometer-sized copper rich precipitates and sub-nanometer defect-solute clusters. We present results of small angle neutron
scattering (SANS) and positron annihilation spectroscopy (PAS) characterization of the nanostructural features formed in
binary and ternary Fe-Cu-Mn alloys irradiated at (approx) 290 degrees C. These complementary techniques provide insight
into the composition and character of both types of nanoscale features. The SANS measurements indicate populations of
copper-manganese precipitates and smaller vacancy-copper-manganese clusters. The PAS characterization, including both
Doppler broadening and positron lifetime measurements, indicates the presence of essentially defect-free Cu precipitates in
the Fe-Cu-Mn alloy and vacancy-copper clusters in the Fe-Cu alloy.
NTIS
Nanostructures (Devices); Irradiation; Pressure Vessels; Nuclear Reactors; Manganese Alloys
20040073496 NASA Marshall Space Flight Center, Huntsville, AL, USA
Studies of Nucleation and Growth, Specific Heat and Viscosity of Undercooled Melts of Quasicrystals and
Polytetrehedral-Phase-Forming Alloys
Biological and Physical Space Research Laboratory 2002 Science Review; December 2003, pp. 19; In English; See also
20040073490; No Copyright; Abstract Only; Available from CASI only as part of the entire parent document
By investigating the properties of quasicrystals and quasicrystal-forming liquid alloys, we may determine the role of
ordering of the liquid phase in the formation of quasicrystals, leading to a better fundamental understanding of both the
quasicrystal and the liquid. A quasicrystal is solid characterized by a symmetric but non-periodic arrangement of atoms,
usually in the form of an icosahedron (12 atoms, 20 triangular faces). It is theorized that the short-range order in liquids takes
this same form. The degree of ordering depends on the temperature of the liquid, and affects many of the liquid s properties,
including specific heat, viscosity, and electrical resistivity. The MSFC role in this project includes solidification studies, phase
diagram determination, and thermophysical property measurements on the liquid quasicrystal-forming alloys, all by
electrostatic levitation (ESL). The viscosity of liquid quasicrystal-forming alloys is measured by the oscillating drop method,
both in the stable and undercooled liquid state. The specific heat of solid, undercooled liquid, and stable liquid are measured
by the radiative cooling rate of the droplets.
Author
Melts (Crystal Growth); Liquid Alloys
20040073508 NASA Marshall Space Flight Center, Huntsville, AL, USA
Effects of Traveling Magnetic Field on Dynamics of Solidification
Biological and Physical Space Research Laboratory 2002 Science Review; December 2003, pp. 15; In English; See also
20040073490; No Copyright; Abstract Only; Available from CASI only as part of the entire parent document
The Lorentz body force induced in electrically conducting fluids can be utilized for a number of materials processing
technologies. An application of strong static magnetic fields can be beneficial for damping convection present during
solidification. On the other hand, alternating magnetic fields can be used to reduce as well as to enhance convection. However,
only special types of time dependent magnetic fields can induce a non-zero time averaged Lorentz force needed for convection
control. One example is the rotating magnetic field. This field configuration induces a swirling flow in circular containers.
Another example of a magnetic field configuration is the traveling magnetic field (TMF). It utilizes axisymmetric
magnetostatic waves. This type of field induces an axial recirculating flow that can be advantageous for controlling axial mass
transport, such as during solidification in long cylindrical tubes. Incidentally, this is the common geometry for crystal growth
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