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Numerical Modeling of the Stability of Face-Centered Cubic Metals with High Vacancy Concentration

Description: The objective of this research is to assess the possibility of forming an atomically porous structure in a low-density metal, e.g., Al with vacancies up to 0.20/lattice site; and to examine the effects of hydrogen and vacancy concentration on the stability of an atomically porous structure that has been experimentally produced in nickel. The approach involves numerical modeling using the Embedded-Atom Method (EAM). High vacancy concentrations cause the Al lattice to disorder at 300K. In contras… more
Date: December 1, 1998
Creator: Somerday, Brian P. & Baskes, M. I.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Point Defect Cluster Formation in Iron Displacement Cascades Up to 50 keV

Description: The results of molecular dynamics displacement cascade simulations in iron at energies up to 50 keV and temperatures of 100, 600, and 900K are summarized, with a focus on the characterization of interstitial and vacancy clusters that are formed directly within the cascade. The fraction of the surviving point defects contained in clusters, and the size distributions of these in-cascade clusters have been determined. Although the formation of true vacancy clusters appears to be inhibited in iron,… more
Date: November 30, 1998
Creator: Stoller, R.E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Evaluation of the intrinsic and extrinsic fracture behavior of iron aluminides

Description: Iron aluminides have excellent corrosion resistance in high-temperature oxidizing-sulfidizing environments; however, there are problems at room and medium temperatures with hydrogen embrittlement as related to exposure to moisture. In this research, a coordinated computational modeling/experimental study of mechanisms related to environmental-assisted fracture behavior of selected iron aluminides has been undertaken. The modeling and the experimental work connect at the level of coordinated und… more
Date: July 27, 1998
Creator: Cooper, B. R. & Kang, B. S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Vacancy supersaturations produced by high-energy ion implantation

Description: A new technique for detecting the vacancy clusters produced by high-energy ion implantation into silicon is proposed and tested. This technique takes advantage of the fact that metal impurities, such as Au, are gettered near one-half of the projected range ({1/2}R{sub p}) of MeV implants. The vacancy clustered region produced by a 2 MeV Si{sup +} implant into silicon has been labeled with Au diffused in from the front surface. The trapped Au was detected by Rutherford backscattering spectrometr… more
Date: January 1, 1998
Creator: Venezia, V.C.; Eaglesham, D.J.; Jacobson, D.C.; Gossmann, H.J.; Haynes, T.E.; Agarwal, A. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Room temperature tensile properties of Fe-Al single crystals strengthened by excess vacancies

Description: Effects of supersaturated excess vacancies on plastic deformation of Fe-Al were investigated by tensile testing at room temperature three different single crystals (Fe-33, 41 and 44mol.% Al). Critical resolved shear stresses (CRSSs) of slowly-cooled specimens (as-homogenized specimens) and well-annealed specimens (vacancy-eliminated specimens) were almost the same and did not show A1 concentration dependence. On the other hand, the CRSS of vacancy-containing specimens (fast-cooled specimens) wa… more
Date: February 1, 1998
Creator: Yoshimi, K.; Saeki, Y.; Hanada, S. & Yoo, M.H.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Layered manganites : magnetic structure at extreme doping levels.

Description: We report powder neutron diffraction results on the crystal and magnetic structures of the bilayer Ruddlesden-Popper phase Sr{sub 3}Mn{sub 2}O{sub 7{minus}{delta}} ({delta} = 0.0, 0.45) and correlate these structures with their magnetic and transport properties. The {delta} = 0.45 compound contains a large number of oxygen vacancies that are disordered in the MnO{sub 2} planes. As a result of this disordered vacancy structure, Sr{sub 3}Mn{sub 2}O{sub 6.55} is a nonmagnetic insulator. Sr{sub 3}M… more
Date: September 11, 1998
Creator: Mitchell, J. F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Room-temperature serrated-flow behavior in Fe-rich FeAl under vacancy supersaturation

Description: In Fe-rich FeAl, serrated plastic-flow behavior has been observed for the first time at room temperature. Serration on the tensile stress-strain curve occurs in single crystals that retained supersaturation of thermal vacancies after fast-cooling from the annealing temperature of 1173 K. In contrast to conventional serrated flow, the serrated flow in FeAl is associated with work hardening, and it becomes more pronounced with increasing Al content from 33 to 44 mol.%. The experimental results ar… more
Date: November 1998
Creator: Yoshimi, K.; Yoo, M.H. & Hanada, S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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