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Effect of sulfur on the ductility of copper shaped-charge jets

Description: We have observed that a change in bulk sulfur (S) content imposed by doping has a marked effect on ductility of copper shaped-charge jets as measured by breakup times and length-to-diameter ratios of the particulated jet. Baseline material was Oxygen-Free-Electronic (ofe) copper with a S concentration of 3-4 ppM. Several liners were doped using a Cu sulfide powder pack method to increase the S level up to 9 ppM, while keeping other impurities and microstructure unchanged. Using flash x-ray radiographs to record the formation of jets, both the length-to-diameter ratios of the jet particles and breakup times were measured. Increasing the bulk S content of ofe Cu to 9 ppM, the breakup times decreased from 186 to 147 {mu}s, while the length-to- diameter ratios observed at 260 {mu}s decreased from 8:1 to 5:1. Since the solubility of S in Cu at the processing temperatures is extremely low, we conclude that the bulk rise in S content is due to S segregating to the grain boundaries. Thus, the decrease in ductility of liners doped with S appears directly related to the S content at the grain boundaries.
Date: July 1, 1996
Creator: Lassila, D.H.; Chan, D.K.; King, W.E.; Schwartz, A.J. & Baker, E.L.
Partner: UNT Libraries Government Documents Department

The effect of potential on the high-temperature fatigue crack growth response of low alloy steels: Part II, electrochemical results

Description: Environmentally assisted cracking (EAC) in low alloy steels was found to be dependent on externally applied potential in low sulfur steels in high temperature water. EAC could be turned on when the specimen was polarized anodically above a critical potential. However, hydrogen (H) additions inhibited the ability of potential to affect EAC. The behavior was related to formation of H ions during H oxidation at the crack mouth. A mechanism based on formation of H sulfide at the crack tip and H ions at the crack mouth is presented to describe the process by which sulfides and H ions affect the critical sulfide concentration at the crack tip.
Date: April 1, 1997
Creator: Moshier, W.C. & James, L.A.
Partner: UNT Libraries Government Documents Department

Photovoltaic Devices Employing Ternary PbSxSe1-x Nanocrystals

Description: We report solar cells based on highly confined nanocrystals of the ternary compound PbSxSe1-x. Crystalline, monodisperse alloyed nanocrystals are obtained using a one-pot, hot injection reaction. Rutherford back scattering and energy filtered transmission electron microscopy suggest that the S and Se anions are uniformly distributed in the alloy nanoparticles. Photovoltaic devices made using ternary nanoparticles are more efficient than either pure PbS or pure PbSe based nanocrystal devices.
Date: February 5, 2009
Creator: Ma, Wanli; Luther, Joseph; Zheng, Haimei; Wu, Yue & Alivisatos, A. Paul
Partner: UNT Libraries Government Documents Department

Corrosion fatigue crack growth in clad low-alloy steel. Part 2, Water flow rate effects in high sulfur plate steel

Description: Corrosion fatigue crack propagation tests were conducted on a high- sulfur ASTM A302-B plate steel overlaid with weld-deposited Alloy EN82H cladding. The specimens featured semi-elliptical surface cracks penetrating approximately 6.3 mm of cladding into the underlying steel. The initial crack sizes were relatively large with surface lengths of 22.8--27.3 mm, and depths of 10.5--14.1 mm. The experiments were initiated in a quasi-stagnant low-oxygen (O{sub 2} < 10 ppb) aqueous environment at 243{degrees}C, under loading conditions ({Delta}K, R, cyclic frequency) conducive to environmentally-assisted cracking (EAC) under quasi-stagnant conditions. Following fatigue testing under quasi-stagnant conditions where EAC was observed, the specimens were then fatigue tested under conditions where active water flow of either 1.7 m/sec. or 4.7 m/sec. was applied parallel to the crack. Earlier experiments on unclad surface-cracked specimens of the same steel exhibited EAC under quasi- stagnant conditions, but water flow rates at 1.7 m/sec. and 5.0 m/sec. parallel to the crack mitigated EAC. In the present experiments on clad specimens, water flow at approximately the same as the lower of these velocities did not mitigate EAC, and a free stream velocity approximately the same as the higher of these velocities resulted in sluggish mitigation of EAC. The lack of robust EAC mitigation was attributed to the greater crack surface roughness in the cladding interfering with flow induced within the crack cavity. An analysis employing the computational fluid dynamics code, FIDAP, confirmed that frictional forces associated with the cladding crack surface roughness reduced the interaction between the free stream and the crack cavity.
Date: April 1, 1996
Creator: James, L.A; Lee, H.B.; Wire, G.L.; Novak, S.R. & Cullen, W.H.
Partner: UNT Libraries Government Documents Department

Investment cast AISI H13 tooling for automotive applications

Description: While many techniques exist for production of soft tooling, for die casting there is limited recent experience with cast tooling. The most common US alloy used for manufacture of die casting tooling is wrought AISI H13. If the performance of the cast material is comparable to the wrought counterpart, the use of investment cast HI 3 tooling directly from patterns made via rapid prototyping is of considerable interest. A metallurgical study of investment cast H13 was conducted to evaluate the mechanical behavior in simulated die casting applications. Variable thickness plate investment castings of AISI H13 hot work die steel were produced and characterized in the as-cast and heat-treated conditions. The characterization included light microscopy and mechanical testing. Wrought samples of standard and premium grade H13 were heat-treated and characterized similarly for comparison. Microstructural differences were observed in as-cast samples produced in different section thicknesses. Dendrite cell size and carbide morphology constituted the most prominent microstructural differences observed. After a full heat-treatment, microstructural differences between the wrought material and cast materials were slight regardless of section thickness.The mechanical properties of the cast and heat-treated material proved similar to the properties of the standard heat-treated wrought material. A thermal fatigue testing unit was to con-elate the heat checking susceptibility of H13 steel to its processing and consequent microstructural condition. Surface hardness decreased significantly with thermal cycling, and heat checking was observed in as few as 50 cycles. Thermal softening and thermal fatigue susceptibility were quantified and discussed relative to the microstructural conditions created by processing and heat-treatment. It was found that the premium grade wrought H13 steel provided the best overall resistance to heat checking.
Date: July 1, 1995
Creator: Maguire, M.C.; Baldwin, M.D.; Hochanadel, P.W. & Edwards, G.R.
Partner: UNT Libraries Government Documents Department

Effect of heat treatment and impurity concentration on some mechanical properties V-15Cr-5Ti alloy

Description: The effects of heat treatment and O, N, C, Si, and S impurity level on the yield strength, ductility, and fracture mode for specimens from four different heats of the V-15Cr-5Ti alloy are presented. The heat treatments for the alloy consisted of annealing as-rolled material for one hour at either 950, 1050, 1125, or 1200/sup 0/C. The total oxygen, nitrogen, and carbon impurity concentration ranged from 400 to 1200 wppm. The Si concentration ranged from 300 to 1050 wppm, and the S concentration ranged from 440 to 1100 wppm. The yield strength and ductility for the alloy, regardless of impurity concentration, exhibited minimum and maximum values, respectively, for the 1125/sup 0/C anneal. The primary mode of failure for the tensile specimens was transgranular fracture.
Date: March 1, 1986
Creator: Loomis, B.A.; Kestel, B.J. & Diercks, D.R.
Partner: UNT Libraries Government Documents Department

DX centers in III-V semiconductors under hydrostatic pressure. [GaAs:Si; InP:S]

Description: DX centers are deep level defects found in some III-V semiconductors. They have persistent photoconductivity and large difference between thermal and optical ionization energies. Hydrostatic pressure was used to study microstructure of these defects. A new local vibrational mode (LVM) was observed in hydrostatically stressed, Si-doped GaAs. Corresponding infrared absorption peak is distinct from the Si[sub Ga] shallow donor LVM peak, which is the only other LVM peak observed in our samples, and is assigned to the Si DX center. Analysis of the relative intensities of the Si DX LVM and the Si shallow donor LVM peaks, combined with Hall effect and resistivity indicate that the Si DX center is negatively charged. Frequency of this new mode provides clues to the structure of this defect. A pressure induced deep donor level in S-doped InP was also discovered which has the properties of a DX center. Pressure at which the new defect becomes more stable than the shallow donor is 82 kbar. Optical ionization energy and energy dependence of the optical absorption cross section was measured for this new effect. Capture barrier from the conduction band into the DX state were also determined. That DX centers can be formed in InP by pressure suggests that DX states should be common in n-type III-V semiconductors. A method is suggested for predicting under what conditions these defects will be the most stable form of the donor impurity.
Date: November 1, 1992
Creator: Wolk, J.A.
Partner: UNT Libraries Government Documents Department

Microstructure and hydriding studies of AB/sub 5/ hydrogen storage compounds. Final report

Description: New data on the microstructure, pressure-composition-temperature, and absorption/desorption kinetics of AB/sub 5/ metal hydrides are presented. The most significant result to emerge from the investigation is that many of the AB/sub 5/ metal hydrides, especially the LaNi/sub 5/ related materials, show instantaneous absorption and desorption response in proportion to the amount of cooling or heating which is provided. Eight categories of materials were studied: reference alloys (LaNi/sub 5/, LaNi/sub 4/ /sub 9/Al/sub 0/ /sub 1/, LaNi/sub 3/Co/sub 2/); Ni second phase particles (LaNi/sub 5/ /sub 67/, LaNi/sub 7/, LaNi/sub 11/ /sub 3/); eutectoid microstructure (SmCo/sub 5/); other second phases (LaNi/sub 3/ /sub 8/Fe/sub 1/ /sub 2/, LaNi/sub 3/ /sub 5/Cr/sub 1/ /sub 5/, LaNi/sub 4/Cr, LaNi/sub 4/Si; LaNi/sub 4/Sn, MNi/sub 4/Sn, MNi/sub 4/ /sub 3/Al/sub 0/ /sub 7/); substitutional elements (LaNi/sub 4/Cu, LaNi/sub 4/ /sub 5/Pd/sub 0/ /sub 5/, LaNi/sub 4/ /sub 7/Sn/sub 0/ /sub 3/, LaNi/sub 4/ /sub 8/C/sub 0/ /sub 2/, MNi/sub 4/ /sub 3/Mn/sub 0/ /sub 7/); surface active elements (LaNi/sub 4/ /sub 8/B/sub 0/ /sub 2/, LaNi/sub 4/ /sub 9/S/sub 0/ /sub 1/, LaNi/sub 4/ /sub 9/Se/sub 0/ /sub 1/); large diameter atom substitutions (Mg/sub 0/ /sub 1/La/sub 0/ /sub 9/Ni/sub 5/, Ca/sub 0/ /sub 2/La/sub 0/ /sub 8/Ni/sub 5/, Sr/sub 0/ /sub 2/La/sub 0/ /sub 8/Ni/sub 5/, Ba/sub 0/ /sub 2/La/sub 0/ /sub 8/Ni/sub 5/); other compositions (LaNi/sub 3/); and Pd plating (electroless plated samples and mechanically alloyed specimens).
Date: January 1, 1980
Creator: Goodell, P.D.; Sandrock, G.D. & Huston, E.L.
Partner: UNT Libraries Government Documents Department