Results 1 - 10 of 2003
Results 1 - 10 of 2003. Search took: 0.022 seconds
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[en] For the commercial alluminium, normally used in the condutable cable production, were inoculated atomic portions between 0.02% and 0.2% of titanium and niobium elements. The titanium-boro, used as grain refiner. The niobium was inoculated as alloy and halogen salt. The effects of such elements on the grain size, about the electric conductibility and about the stress ultimate strenght of commercial alluminium are studied. (E.G.)
[pt]Para o aluminio comercial, normalmente utilizado na producao de cabos condutores, foram inoculados em porcentagens atomicas entre 0,02% e 0,2% os elementos Titanio e Niobio. O Titanio-Boro, de uso corrente como refinador de grao. O Niobio foi inoculado na forma de liga-mae e de sal halogenio. Discute-se efeitos de tais elementos sobre o tamanho de grao, sobre a condutibilidade eletrica e sobre o limite de resistencia a tracao do aluminio comercial utilizado. (Autor)
[en] Titanium distribution and its effect on the structure of Nb/Cu-Sn composite different components at introduction of this alloying element into bronze matrix in 0.2 mas.% amount, are studied. Titanium during annelainmg is detrermined to diffuse from bronze matrix via Nb3Sn layer into niobium filaments. In this case, increase of growth rate for diffusion layer is observed, and as a result, growth of its thickness, anisotropy of grain form reduces, though no grin refinement is detected. Thermodynamic and kinetic justification of titanium redistribution along composite components at introduction of this alloying addition both into bronze matrix and into niobium filaments is given
[en] We report on a 520-µJ, 1-kHz mid-infrared femtosecond optical parametric amplifier system driven by a Ti:sapphire laser system. The seeding signal was generated from white-light continuum in YAG plate and then amplified in four non-collinear amplification stages and the idler was obtained in the last stage with central wavelength at 2.8 µm and bandwidth of 525 nm. To maximize the bandwidth of the idler, a theoretical method was developed to give an optimum non-collinear angle and estimate the conversion efficiency and output spectrum. As an experimental result, laser pulse energy up to 1.8 mJ for signal wave and 520 µJ for idler wave were obtained in the last stage under 10-mJ pump energy, corresponding to a pump-to-idler conversion efficiency of 5.2%, which meets well with the numerical calculation.
[en] Prime Candidate Alloy (PCA) has been rapidly solidified and its composition has been modified by increasing carbon and titanium content. Rapidly solidified Path A alloy, with a fine grain size (approximately 5 μm) and controlled TiC dispersion, showed good room temperature tensile properties and favorable rupture strength and ductility at 923 K in the preirradiated condition. Structural modifications which include a reduction of grain size, an increase in TiC content and a control of dislocation structure are expected to have a beneficial effect on high temperature strength and swelling of Path A alloys under irradiation
[en] In early 1977 the National Materials Advisory Board, an operating unit in the Commission on Sociotechnical Systems of the National Research Council, NAS/NAE, formed a study committee on High Density Materials for Kinetic Energy Penetrators. The Specific objectives of the Committee were defined as follows. Assess the potential of two materials for use in kinetic energy penetrators, including such factors as: (a) properties (as applied to this application: strength, toughness, and dynamic behavior); (b) uniformity, reliability and reproducibility; (c) deterioration in storage; (d) production capability; (e) ecological impact; (f) quality assurance; (g) availability, and (h) cost. The Committee was divided into two Panels; one panel devoted to the study of tungsten alloys and the other devoted to the study of depleted uranium alloys for use in Kinetic energy penetrators. This report represents the findings and recommendation of the Panel on Uranium
[en] The paper presents investigations of bainitic in two experimental Fe-Cr-Mo-C and Fe-Cr-Mo-Ti-C steels. Heat treatment was planned on the basis of dilatometric analysis and thermodynamic calculations taking into account chemical compositions of the investigated steels. Microstructure was investigated using optical metallography and TEM method. After austenization at 1200 C followed by bainitic reaction in lower temperatures of isothermal transformation, the bainite was in the form of classical sheaves only when a prior austenite grain boundaries were not covered by allotriomorphic ferrite. The development of bainitic transformation, the amount, distribution and morphology of retained austenite and morphology of bainite ferrite strongly depend on both the prior austenization and isothermal transformation temperature within the bainitic range. (author). 24 refs, 11 figs, 3 tabs
[en] We report on the longitudinally pumped tunable single- and dual-wavelength nanosecond Ti:Sapphire laser operation around 765 nm by using a Brewster-cut single Ti:Sapphire crystal in combination with an intracavity prism and etalon. Tilting the etalon to a specific angle, single-wavelength operation at 767.9 nm is achieved first, with a maximum output power value of 1.3 W below 5.5 W pump power. Then, increasing the pump power leads to simultaneously operation at dual wavelength (765.0, 771.3 nm), (763.9, 772.2 nm), (763.5, 772.2 nm), and (762.4, 773.7 nm) with a maximum output power of ~ 2.98 W, pulse width of ~ 20 ns, and a laser slope efficiency of about 34.7% at 1 kHz repetition rate. By tilting the etalon, other dual- and single-wavelength laser operations could be achieved. Experimental results show that it is tunable in the region 750–840 nm which here is limited by the reflectivity of the cavity mirrors. We observed, when laser oscillates at dual wavelength, the separation of the wavelengths increased with pump power which could be because of thermal lensing in Ti:Sapphire. The output characteristics versus incident pump power at 1 and 5 kHz repetition rate show output power increases linearly with incident pump power with similar slope for both 1 and 5 kHz repetition rates, whereas pump threshold increased in the case of 5 kHz.
[en] Highlights: ► The electrochemical behaviour of three ZrTi alloys in saline and in Ringer's solutions has been characterized. ► ZrTi alloys attain a passive regime when immersed in Ringer's solution, and this happens spontaneously at the open circuit potential. ► Titanium addition to zirconium results in greater corrosion resistance and thicker passive films, less susceptible to localized corrosion. ► Localized differences in electrochemical reactivity of the materials could be established by SECM measurements. ► Polarization of the alloys at anodic polarizations that can be achieved in the human body leads to an increase in surface reactivity. -- Abstract: The electrochemical behaviour of three ZrTi alloys (Zr5Ti, Zr25Ti and Zr45Ti) in Ringer's solution has been investigated. Their resistance against localized corrosion has been determined from cyclic potentiodynamic polarization (CCP) and electrochemical impedance spectroscopy (EIS) measurements, whereas scanning electrochemical microscopy (SECM) was applied to investigate the local reactivity of the passive films developed on the materials, and scanning electron microscopy (SEM) was employed to characterize the surface morphology of the alloys subjected to anodic polarization. An increased reactivity could be detected with SECM when the metal samples were polarized at +0.50 VSHE, though the extent of this feature greatly depended on the nature of the metallic material. In addition, At 37 °C, the Zr5Ti alloy was susceptible to localized corrosion. Though Zr25Ti alloy presented rather low pitting potential, the spontaneous corrosion potential of the material was sufficiently negative to require overpotentials around 600 mV for breakdown to occur. Finally, the Zr45Ti alloy exhibited a larger passive range in the polarization curve, and it was resistant to localized corrosion