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[en] Based on the critically assessed B-Si phase diagram, one alloy in the Si-rich side was selected and the temperature of the eutectic reaction L ↔ (Si) + SiB6 was measured to be 1636 K by means of DSC. Using a regular substitutional model for the liquid phase, the B-Si system was reassessed and extrapolated to higher-order systems. Thermodynamic description for the B-C-Si system was developed based on critically reviewed experimental data. The calculated phase diagrams were in good agreement with available experimental data.
[en] Strain dependent damping measurements of the widely used commercial cast magnesium alloy AZ91 (Mg+9 wt.% Al+1 wt.% Zn) were carried out under controlled fatigue bending loading. Damping was determined at room temperature as the logarithmic decrement of freely decaying vibrations of a bending beam clamped at one side. With increasing number of vibrations a maximum in the amplitude dependent damping curves for strains from 10-5 up to 10-3 was measured which can be attributed to the presence of cracks contributing to the dissipation of energy by displacement of crack surfaces. This maximum shifts to lower strains with rising number of loading cycles and is correlated with crack growth. A simple rheological model on crack damping is discussed
[en] Far-infrared transmission spectra of Ge0.17Se0.83-xSbx (x = 0, 0.03, 0.09, 0.12, 0.15) glassy alloys are obtained in the spectral range 500-200 cm-1 at room temperature. The results are interpreted in terms of the vibrations of the isolated molecular units, in such a way as to preserve fourfold and twofold coordination for Ge and Se atoms, respectively. In the Ge0.17Se0.83 bulk glass the main absorption bands appear at ∼250 cm-1 and 300 cm-1. With the increase in Sb content some new bands start appearing at 228-231 cm-1 and 250-260 cm-1. Theoretical calculations (bond energy, relative probability density of bond formation, force constant and wave number) were also made to justify the results.
[en] The effect of different Wire electrical discharge machining (WEDM) process parameters on the damping behavior of A356.2 aluminum alloy is investigated. In the present investigation pulse on time (T_O_N), pulse off time (T_O_F_F) and peak current (IP) which are considered to be the most significant process parameters from the previous studies are varied using one factor at a time approach, to study the effect on damping behavior of A356.2 aluminum alloy. Damping experiments are performed on a dynamic mechanical analyzer (DMA 8000) at constant strain under dual cantilever mode over a frequency range of 1–100 Hz at room temperature. The scanning electron microscope was used for characterization of the wire EDMed samples. Experimental results reveal that the damping behavior greatly depends on the wire EDM process parameters. The related mechanisms are presented. - Highlights: • Damping capacity increase with the increase in frequency. • Increasing pulse on time increases the damping capacity of aluminum alloy. • The damping capacity was found to decrease with the increase in pulse off time. • No significant change in damping capacity was noticed with varied peak current. • The formation of white layer plays an important role in the damping behavior
[en] The crystallographic and magnetic structures of Er6Ni2Sn have been determined at low temperatures using neutron powder diffraction. It has been found that this system orders antiferromagnetically (AF) below TN = 17 K. Data taken at low temperatures and analyzed using symmetry group analysis suggest that Er6Ni2Sn forms a complex non-collinear commensurate AF structure with strongly reduced Er magnetic moments. The reason for the reduced moments is unclear and needs further studies. The magnetic phases below 7 K and in the temperature range 7-17 K differ only in the Er magnetic moment magnitudes and in the angle that the Er moments at the 8l site make with the c-axis. The extra reflections present in the powder diffraction patterns suggest presence of a secondary phase. The temperature evolution of the powder pattern indicates that the secondary phase orders AF at 35 K
[en] Magnetic properties and magnetocaloric effect (MCE) of intermetallic Dy3Al2 compound have been investigated systematically. Two successive magnetic transitions, a paramagnetic–ferromagnetic transition at TC = 94 K followed by a spin reorientation around TSR = 69 K, are observed with the variation of temperature. Large permanent magnetic properties at low temperatures, i.e., the coercivity Hci and maximum energy product (BH)max at 5 K are 26.0 kOe and 58.5 MGOe, respectively, suggest Dy3Al2 compound as attractive candidate for low-temperature permanent magnets. For a magnetic field change of 50 kOe, two successive magnetic entropy change (ΔSM) peaks of 5.2 and 12.1 J/kg K are observed around TSR and TC, respectively. These two ΔSM peaks overlap partly, and thus giving rise to a high refrigerant capacity (RC = 360 J/kg at 50 kOe) over a wide temperature span. The universal curve of successive ΔSM peaks is constructed by using a phenomenological procedure. It is found that not only the curves under different magnetic field changes but also the curves around different transitions collapse onto the nearly same universal curve. Our result suggests that the phenomenological construction of universal curve is applicable in materials with successive second-order phase transitions. - Highlights: • The universal curve of successive ΔSM peaks is constructed for the first time by using a phenomenological procedure. • The successive ΔSM peaks leads to a large RC, which is higher than those of some materials in same temperature range. • Dy3Al2 exhibits a higher permanent magnetic property than those of other materials at low temperature.
[en] The magnetization of Fe/Y multilayers has been measured as a function of temperature. A bulk-like T 3/2 temperature dependence of the magnetization is observed for all multilayers in the temperature range 5-300 K. The spin-wave constant B is found to decrease inversely with t Fe. A simple theoretical model with exchange interactions only, and with non-interacting magnons, has been used to explain the temperature dependence of the magnetization and the approximate values for the bulk exchange interaction J b, surface exchange interaction J s and the interlayer exchange interaction J I for various Fe layer thicknesses have been obtained
[en] Fe/V multilayers prepared by sputtering has been studied by conversion electron Moessbauer spectroscopy. An extended series of samples of the Fe(x)/V(y) system has been studied both at room temperature and at 10 K. The series consisted of samples with x=3 ML (monolayers), 5 ML, 7 ML, 10 ML and 20 ML and y=5 ML, 10 ML and 14 ML. The obtained hyperfine field distributions point to quite diffuse interfaces, where multilayers with Fe layer thickness less than 5 ML are mainly non-magnetic. The influence of the spacer layer thickness on the Fe hyperfine field has also been investigated. The results indicate that interlayer coupling may influence the hyperfine field distribution positively
[en] The enthalpy of formation of the Cd-Te solid and liquid alloys was measured by direct reaction calorimetry (DRC) (drop method) at 737 and 1259 K with the help of a Tian-Calvet high temperature calorimeter. The DRC procedure used was very simple at 737 K but more sophisticated at 1259 K due to the high vapor pressures of both components. This allowed us to determine the enthalpy of formation of the CdTe solid compound in agreement with the data of the literature and the enthalpy of formation of the melts in the whole range of concentration. (orig.)
[en] DSC measurements were carried out for various Fe100-xAl x(x = 5-30 at%) alloys to clear the effects of cold roll and quenching rate from 1173 K. In the case of cold roll free specimens, an exothermic peak was observed at around 530-560 K in quenched specimens and no peaks in slowly cooled specimens. The peak temperature and its exothermic heat depended on the alloy composition. The maximum exothermic heat was obtained for a 25 at% Al alloy and its value were about 1200 J/mol. The peak in a 5 at% Al alloy was remained as a future work. The exothermic heat was affected by the quenching temperature in alloys above 15 at% Al. The peak temperature was decreased by decreasing the quenching temperature. In a 15 at% Al alloy, the peak became negligibly small by quenching from 1023 K. The activation energies in cold roll free specimens were evaluated from the Kissinger analysis and they were 134, 108, 133 and 110 kJ/mol for 15 at% Al, 20 at% Al, 25 at% Al and 30 at% Al alloys, respectively. On the other hand, cold rolled specimens showed an exothermic peak at around 470 K, independently of the cooling rate. Their exothermic heats and temperatures were comparable order to those of furnace cooled and water quenched specimens. The present results suggested that origin of exothermic peaks of all alloys were same in nature and atomic ordering may be related to the exothermic behavior at relatively low temperatures