Results 1 - 10 of 334
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[en] In this study, monotonic, cyclic and fatigue properties of the A356 aluminum alloy were identified using torsion tests with rounded solid test specimens of the alloy in four different processing conditions. The monotonic and cyclic shear stress-strain behaviors of the alloys are described using the Ramberg-Osgood model and the materials constitutive parameters were estimated minimizing the difference between the experimental torque and the analytical value. Results of torsion fatigue tests with R = −1 were compared with rotating bending results and the load factor was evaluated. Experimental fatigue results indicated that the alloys at T6 condition showed the best behavior and the results of strontium modified alloys shown slightly lower performance. The fatigue life diagram of T6 alloys has steeper negative slope (shear fatigue strength exponent, b ≅ −0.2) than the others as cast alloys (b ≅ −0.06). The comparisons of experimental rotating bending and reverse torsion fatigue showed exponent b is dependent on the load type for the as cast alloys. For the heat-treated alloys, the variation of exponent b is minimal and its value can be considered constant. (paper)
[en] For the first time strontium activity in liquid alloys with bismuth has been determined. Values of strontium activity coefficients point out to abrupt negative deviation from ideal behaviour of liquid strontium alloys with bismuth which testifies to a strong interparticle interaction in liquid state and agrees with state diagram of this system
[en] The dielectric properties of the uniaxial relaxor ferroelectric SrxBa1−xNb2O6 with x = 0.75 were investigated along the polar  direction as a function of temperature. The capacitance maximum showed the frequency dispersion commonly observed in relaxors. Additional weak dielectric anomalies were observed in the paraelectric phase; they were only seen during the heating process and disappeared upon subsequent cooling. These were attributed to the existence of large polar clusters strongly pinned at defects and/or to random fields and their metastable characters. Aligning the ferroelectric domains along the polar axis at room temperature removed the high-temperature dielectric anomalies. The dependences of the capacitance and the dielectric maximum temperature on the magnitude of the poling field were investigated.
[en] The deriving master alloys Al-(1-5)%Sr and Al-12%Si-(1-5)%Sr by alumothermal reducing of strontium from its carbonate has been mastered. The high modifying ability of master alloys for hypoeutectic alloy Al-Si has been shown
[ru]Освоено получение лигатур Al-(1-5)%Sr и Al-12%Si-(1-5)%Sr путем алюминотермического восстановления стронция из его карбоната. Показана высокая модифицирующая способность лигатур применительно к доэвтектическому сплаву Al-Si
[en] n the superconducting Sr2VO3FeAs, containing bimetallic layers, with maximum Tc≅46 K correlation effects on V ions have been investigated using LDA+U method. Within the local density approximation (LDA) this system has the one-third filled t2g manifold of V, decomposed into dxy of bandwidth W=2 eV and nearly degenerate dzxdyz of W=1 eV. Consideration of correlation effects leads to a metal-insulator transition on V ions t2g2↑ → dxz1↑dyz1↑ at the critical on-site Coulomb repulsion Uc= 3.5 eV. At U=4 eV, the electronic structure, in which V ions are insulating, leads to several van Hove singularities near EF and similar Fermiology with other pnictides. Applying U to V ions results in increasing Fe moment as well as V moment, indicating somewhat hybridization between Fe and V ions even though this system is strongly 2-dimensional. Our results show possible importance of correlation effects on this system.
[en] Using an X-ray Diffractometer (XRD) technique, several peaks from diffraction lines of various mixtures of PbSn are obtained. By using the Scherrer equation, the crystallite size at the peak of (200) is calculated for all the mixtures. (author)