NASA Scientific and Technical Aerospace Reports

20040111168 California Univ., Lawrence Berkeley National Lab., Berkeley, CA, USA, California Univ., Davis, CA, USA,
Los Alamos National Lab., NM, USA
Atomistic Simulations of fcc Pt(75)Ni(25) and Pt(75)Re(25) Cubo-octahedral Nanoparticles
Wang, G.; Van Hove, M. A.; Ross, P. N.; Baskes, M. I.; 2004; 10 pp.; In English
Report No.(s): DE2004-822978; No Copyright; Avail: Department of Energy Information Bridge
We have developed interatomic potentials for Pt-Ni and Pt-Re alloys within the modified embedded atom method
(MEAM). Furthermore, we applied these potentials to study the equilibrium structures of Pt75Ni25 and Pt75Re25
nanoparticles at T=600 K using the Monte Carlo method. In this work, the nanoparticles are assumed to have disordered fcc
cubo-octahedral shapes (terminated by (111) and (100) facets) and contain from 586 to 4033 atoms (corresponding to a
diameter from 2.5 to 5 nm). It was found that, due to surface segregation, (1) the Pt75Ni25 nanoparticles form a
surface-sandwich structure: the Pt atoms are enriched in the outermost and third atomic shells, while the Ni atoms are enriched
in the second atomic shell; (2) the equilibrium Pt75Re25 nanoparticles adopt a core-shell structure: a Pt-enriched shell
surrounding a Pt-deficient core.
NTIS
Atoms; Embedded Atom Method; Nanoparticles; Order-Disorder Transformations
20040111181
Development of a Cast Iron Fatigue Properties Database for Use in Modern Design Methods
DeLaO, J. D.; Gundlach, R. B.; Tartaglia, J. M.; 2003; In English
Report No.(s): DE2003-815140; No Copyright; Avail: National Technical Information Service (NTIS)
A reliable and comprehensive database of design properties for cast iron is key to full and efficient utilization of this
versatile family of high production-volume engineering materials. A database of strain-life fatigue properties and supporting
data for a wide range of structural cast irons representing industry standard quality was developed in this program. The
database primarily covers ASTM/SAE standard structural grades of ADI, CGI, ductile iron and gray iron as well as an
austempered gray iron. Twenty-two carefully chosen materials provided by commercial foundries were tested and fifteen
additional datasets were contributed by private industry. The test materials are principally distinguished on the basis of grade
designation; most grades were tested in a 25 mm section size and in a single material condition common for the particular
grade. Selected grades were tested in multiple sections-sizes and/or material conditions to delineate the properties associated
with a range of materials of the given grade.
NTIS
Cast Alloys; Fatigue (Materials); Iron Alloys
20040111307 NASA Langley Research Center, Hampton, VA, USA
A Design of Experiments Approach Defining the Relationships Between Processing and Microstructure for Ti-6Al-4V
Wallace, Terryl A.; Bey, Kim S.; Taminger, Karen M. B.; Hafley, Robert A.; [2004]; 12 pp.; In English; 15th Solid Freeform
Fabrication Symposium, 2-4 Aug. 2004, Austin, TX, USA
Contract(s)/Grant(s): 762-55-LD; No Copyright; Avail: CASI; A03, Hardcopy
A study was conducted to evaluate the relative significance of input parameters on Ti- 6Al-4V deposits produced by an
electron beam free form fabrication process under development at the NASA Langley Research Center. Five input parameters
where chosen (beam voltage, beam current, translation speed, wire feed rate, and beam focus), and a design of experiments
(DOE) approach was used to develop a set of 16 experiments to evaluate the relative importance of these parameters on the
resulting deposits. Both single-bead and multi-bead stacks were fabricated using 16 combinations, and the resulting heights
and widths of the stack deposits were measured. The resulting microstructures were also characterized to determine the impact
of these parameters on the size of the melt pool and heat affected zone. The relative importance of each input parameter on
the height and width of the multi-bead stacks will be discussed. .
Derived from text
Aluminum Alloys; Microstructure; Titanium Alloys; Vanadium Alloys
20040111472 Academy of Sciences of the Ukraine, Kiev
Investigation of Structure, Properties and Deformation Mechanisms of Elevated Temperature Al Alloys with High
Specific Properties
Milman, Yuly V.; Jan. 31, 2004; 113 pp.; In English; Original contains color illustrations
Report No.(s): AD-A425413; EOARD-STCU-00-8005; No Copyright; Avail: CASI; A06, Hardcopy
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