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Elastic and plastic strains and the stress corrosion cracking of austenitic stainless steels. Progress report, April 30, 1977--December 30, 1977

Description: A newly developed test environment based on NaCl, Na/sub 2/SO/sub 4/, and HCl has provided some insight to several aspects of SCC in a transformable austenitic stainless steel. Current vs. time curves indicated the presence of the formation of a ''protective'' film which drastically reduced the anodic current leading to failure. This film, not indicated by the polarization curves, is subject to highly localized damage such as pitting. Thus, although it allows only very small corrosion currents, it is not truly protective. Hence, it is pseudo-passive. The critical cracking potential did not exhibit any difference between the annealed and the maximum (25%) deformation examined. The corrosion or open circuit potential for both annealed and deformed material behaved in a similar manner, becoming more noble with time until it reached the critical cracking potential and SCC ensured. The failure time for the deformed specimens was substantially shorter than for the annealed ones, but the incubation time was essentially the same. Within the range of experimental conditions examined thus far, it appears that the critical parameters leading to SCC in a chloride environment are primarily dependent on surface-environment interactions and not dependent on the bulk properties.
Date: January 1, 1978
Creator: Troiano, A.R.
Partner: UNT Libraries Government Documents Department

Elastic and plastic strains and the stress corrosion cracking of austenitic stainless steels. Progress report, April 30, 1975--December 30, 1975

Description: Homogeneous deformation of type 310 austenitic stainless steel only slightly influenced the corrosion potential in a boiling 3 percent NaCl aqueous environment. The difference in a deaerated solution was of the order of 25 mV and somewhat more for an aerated solution. Elastic strains appeared to have little or no influence on the corrosion potential for fully annealed as well as 10 percent and 25 percent homogeneously deformed 310 steel. Oxygen in the environment shifted the corrosion potential several hundred millivolts in the less active direction. The critical cracking potential in a deaerated 3 percent NaCl solution was approximately the same for the annealed and homogeneously deformed specimens at approximately -125 mV SCE.
Date: December 1, 1975
Creator: Troiano, A.R.
Partner: UNT Libraries Government Documents Department

Solid state physics program. Final report

Description: During the 17 year period of this research, experimental and theoretical investigations were completed in many aspects of cohesive properties of metals and alloys and dielectric properties of various crystals and glasses together with the temperature and pressure derivatives of both properties. Studies of the magnetization and magnetic anisotropy indicate superparamagnetism is common in oligatomic condensed films and any decreased magnetic moment must be associated with surface atoms. Large intrinsic stresses are associated with growth morphology and impurities at grain boundaries. Transport properties in normal metals have been investigated theoretically. A number of basic theorems for disordered systems were derived. (204 references) (auth)
Date: June 1, 1975
Partner: UNT Libraries Government Documents Department

Solid state physics program. Annual progress report

Description: The present status of seven problems tn thin films and sunface physics, six in cohesive and dielectric properties, and two in solid state theory is described. The magnetoresistance of a metal having a spherical Fermi surface, but cubic symmetry for the electron scattering, was calculated by the magnetic- scattering eigenfunction approach. A method was developed for determining accurately the orientation of single crystals from Lane photographs. (auth)
Date: November 1, 1973
Partner: UNT Libraries Government Documents Department

Materials research and evaluation for geothermal corrosion environments. Progress report, December 15, 1974--December 15, 1975. [Ni Co Cr Mo alloy]

Description: Bent beam and self-stressed specimens have been employed and shown to give results consistent with other types of specimens as reported in the literature. All tests have been conducted in the standard NACE, H/sub 2/S environment for initial screening and then in a 20 percent NaCl modified NACE solution. Among the higher strength corrosion resistant alloys, K Monel at 135 ksi yield strength did not fail in either environment at temperatures up to 425/sup 0/F stressed at the yield strength. Age hardenable A286 failed at 325/sup 0/F when stressed to the 190 ksi yield strength, but did not fail when stressed to an overaged yield strength of 135 ksi. A new NiCoCrMo age hardenable alloy heat treated to 220 ksi yield strength and stressed to this value did not fail in either environment at temperatures up to 420/sup 0/F. Also, this material was substantially ''brighter'' after the tests than either the K-Monel or A286.
Date: December 1, 1975
Creator: Troiano, A. R. & Hehemann, R. F.
Partner: UNT Libraries Government Documents Department

Investigations of the biological effects of radiation: a multi-discipline approach. Progress report, September 1, 1976--August 31, 1977

Description: The quasi-free electron attachment rate, k/sub e/, and mobility, ..mu../sub e/, were studied in non-polar solutions using pulsed conductivity techniques. Measurements of k/sub e/ of >50 nitro compounds in liquids have ..mu../sub e/ ranging from <0.1 to 100 cm/sup 2//volt sec at temperatures from -100 to +40/sup 0/C indicated electron-dipole interactions are important in liquids having ..mu../sub e/ < 1 cm/sup 2//volt sec. The Smoluchowski equation was modified to include electron-dipole interactions and calculated k/sub e/'s agreed with observations within +-20%. The cellular enhancement ratio, CER, of nine of the nitro compounds were measured and a correlation between k/sub e/ and CER was found which was used to refine a model of cellular radiosensitization involving quasi-free electrons. Diffusion-controlled k/sub e/'s were observed for several carcinogens and in reversed micellar solutions. Field-dependent k/sub e/'s were measured in liquids having ..mu../sub e/ ranging from 10/sup -4/ to 500 cm/sup 2//volt sec and were found to increase at ..mu../sub e/ < 1 and decrease at ..mu../sub e/ > 70 cm/sup 2//volt sec with increasing field. The ..mu../sub e/ of liquid C/sub 2/H/sub 6/ was measured from -40/sup 0/C through the critical temperature at fields up to 180 kV/cm and a transition from polaron to delocalized electron conduction was observed. A pico-second (ps) pulse conductivity technique was developed and hot electron and/or autoionization processes were observed in tetramethylsilane, TMS, 200 ps after the ionizing pulse. A dose, field, and polarity dependent conductivity spike having a lifetime of 100 ps was observed in TMS and is interpreted as a prebreakdown phenomenon.
Date: September 1, 1977
Creator: Friedell, H.L.
Partner: UNT Libraries Government Documents Department

Repair of DNA treated with. gamma. -irradiation and chemical carcinogens. Progress report, February 1, 1976--February 28, 1977. [Endonuclease reactions in E. coli]

Description: Enzymes from E. coli which recognize damage in DNA due to chemical carcinogens and ..gamma..-irradiation are under study. Endonuclease II, which recognizes DNA treated with methylmethane sulfonate, methylnitrosourea, 7-bromomethyl-12-methylbenz(a)anthracene and ..gamma..-irradiation. Apurinic endonuclease (endonuclease VI) recognizes apurinic and apyrimidinic acid sites. These enzymes have now been purified to homogeneity and separated from exonuclease III which other groups have thought to be identical with one or both of the endonucleases. A series of mutants of E. coli were found to lack one, two, or all of these enzymes. The genetic loci for the two endonucleases are very close to the Exonuclease III locus at 38.2 minutes. An attempt to relate in vivo sensitivity to MMS to lack of specific enzymes has been made. Substrates for endonuclease II have been examined. ..beta..-propiolactone treated DNA has been found to be substrate and details of this are being examined. The nature of the lesion in ..gamma..-irradiated DNA is under investigation. A search for mammalian enzymes which are N-glycosidases is underway.
Date: January 1, 1977
Creator: Goldthwait, D. A.
Partner: UNT Libraries Government Documents Department

Repair of DNA treated with. gamma. -irradiation and chemical carcinogens. Progress report, June 1, 1975--January 31, 1976. [MMS, methylnitrosourea, 7-bromomethyl-12-methylbenz(a)-anthracene, Escherichia coli]

Description: Enzymatic mechanisms of DNA repair are under investigation. From E. coli an endonuclease active on apurinic acid has been separated from endonuclease II active on DNA treated with methylmethane sulfonate, methylnitrosourea, 7-bromomethyl-12-methylbenz(a)anthracene and ..gamma..-irradiation. Mutants have been identified for each enzyme. The purification of both enzymes is proceeding and the mechanism of action of endonuclease II which has both an N-glycosidase and a phosphodiester hydrolase activity is under investigation. Evidence demonstrating exonuclease III is an enzyme separate from the apurinic acid endonuclease and endonuclease II has been accumulated but this is still under investigation. Work has been completed on 7-bromomethyl-12-methylbenz(a)anthracene treated DNA as a substrate and is being continued on the inhibitory effects of phorbol ester on endonuclease II. Finally, the properties of an enzyme from calf liver active on depurinated DNA have been compared with those of a comparable enzyme from calf thymus. Evidence that they are isozymes has been found.
Date: February 1, 1976
Creator: Goldthwait, D. A.
Partner: UNT Libraries Government Documents Department

Spin--wave spectrum of an amorphous ferromagnet

Description: The spin-wave spectruin of an amorphous Heisenberg ferromagnet is calculated by a diagrammatic expansion making use of a transformation due to Taylor and Wu Phys. Rev., B2: 1752 (1970). The upper limit of the spectrum is found to occur at frequencies below that of the corresponding crystalline system, while the low-frequency part of the spectrum is enhanced. Internal van Hove singularities are absent in the spin-wave spectrum of the amorphous ferromagnet. (auth)
Date: January 1, 1973
Creator: Gubernatis, J.E. & Taylor, P.L.
Partner: UNT Libraries Government Documents Department

Dislocation-solute atom interactions in alloys. Technical progress report, February 1, 1973--January 31, 1974

Description: Research is reported in: alloy hardening and softening in bcc metals, effects of solute gradients on strengthening in bcc materials 10 in Nb), mechanical behavior of hydrogenated bcc metals, carbon-vacancy interactions in austenitic alloys, and Snoek anisotrophy in bcc metals. (10 figures, 40 references) (DJC)
Date: October 31, 1973
Creator: Gibala, R.; Vasudevan, A.K.; Sethi, V.K.; Slane, J.A. & Krupitzer, R.P.
Partner: UNT Libraries Government Documents Department

Plastic deformation in oxide ceramics. Progress report, January 1, 1977--December 31, 1977

Description: Research on plastic deformation in oxide ceramics has been undertaken. Specifically, the effects of non-stoichiometry on slip on the ''hard'' slip systems in Al-rich Mg--Al spinel and oxygen-rich UO/sub 2 + x/ single crystals is under investigation. In the case of spinel, dislocation structures in both stoichiometric and alumina-rich specimens deformed in compression at elevated temperatures (1500 to 1900/sup 0/C) have been studied using transmission electron microscopy. Unusual dislocation structures are observed after large plastic strains, which are attributed to extensive climb and unique node reactions are observed which are the result of climb dissociation. This climb dissociation is attributed to the presence of large concentrations of vacancies produced by non-conservative dislocation motion.
Date: September 1, 1977
Creator: Heuer, A.H.
Partner: UNT Libraries Government Documents Department

Dislocation-solute atom interactions in alloys. Technical progress report, February 1, 1975--January 31, 1976

Description: New results were obtained in two major project areas: (1) surface oxide softening and solute gradients in niobium and tantalum, and (2) mechanical properties of Nb--H and Nb--D alloys. The important results include: (a) observation and characterization of an extremely large softening and ductilizing effect of bcc metals (niobium and tantalum) by application of thin (500 to 1000 A) oxide films coupled with injection of a high density of mobile dislocations; (b) determination of the relative strengthening ductility changes caused by hydrogen and deuterium in niobium. (auth)
Date: October 31, 1975
Creator: Gibala, R.; Sethi, V.K. & Fournier, R.
Partner: UNT Libraries Government Documents Department