Ultrafine-grained structure formation in Ti-6Al-4V alloy via warm swaging

The influence of warm swaging on the structure and properties of Ti-6Al-4V alloy was studied. Warm swaging of the alloy in the interval 680-500°C with the total strain of ε=2.66 was found to be resulted in the formation of a homogeneous globular microstructure with a grain size of 0.4μm in both longitudinal and transversal sections. Room temperature tensile strength and tensile elongation of the swaged alloy was 1315MPa and 10.5%, respectively. Ultrafine-grained Ti-6Al-4V alloy produced by swaging exhibited good workability at 600-700°

Ionospheric effects during first 2 hours after the Chelyabinsk meteorite impact

This paper presents the analysis of ionospheric effects in the region close to the Chelyabinsk meteorite explosion at 03:20UT 2013 February 15 from the Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of Sciences (ISTP SB RAS) EKB radar data, and from the Institute of Geophysics of Ural Branch of Russian Academy of Sciences (IG UB RAS) PARUS ionosonde data. Both instruments are located within the IG UB RAS Arti Observatory approximately 200 km northward from the estimated explosion site. According to the data obtained, the ionospheric disturbance caused by the meteorite flyby, explosion, and impact had high dynamics and amplitude. However, it obviously did not lead to a variation in the ionosphere mean parameters in the region above the disturbance center during the first 2 hours. Essential effects, however, were observed at more than 100-200 km from the explosion site and farther up to 1500 km.Comment: 30 pages, 15 figures, submitted to JAST

Twinning-induced formation of nanostructure in commercial-purity titanium

In the present work the influence of various parameters on formation of nano- or ultrafine-grained structure in commercial-purity titanium during large deformation was quantified using TEM and EBSD. The beneficial effect of twinning on the kinetics of microstructure refinement in titanium was revealed. It was shown that deformation twinning (and therefore nanostructure formation) can be intensified via decrease in temperature, increase in the initial grain size and decrease in the impurities content. The minimum grain size at which twinning can still operate in commercial-purity titanium was determined to be ~1μm. It was shown that rolling to a thickness strain of 93% at -196°C resulted in the formation of a microstructure with a grain/subgrain size ~80 n

Ultra cold neutron trap as a tool to search for dark matter with long-range radius of forces

The problem of possible application of an ultracold neutron (UCN) trap as a detector of dark matter particles with long-range radius of forces has been considered. Transmission of small recoil energy in scattering is a characteristic of long-range forces. The main advantage of the ultracold neutron technique lies in possibility of detecting recoil energy as small as $10^{-7}$ eV. Here are presented constraints on the interaction potential parameters: $U(r)=a r^{-1} e^{-r/\lambda}$ for dark matter particles and neutrons, as well as on the density value of long-range dark matter on the Earth. The possible mechanism of accumulation of long-range dark matter on the Earth surface is considered and the factor of density increase on the Earth surface is evaluated. The results of the first experiment on search of astronomical day variation of ultracold neutron storage time are under discussion.Comment: 17 pages, 19 figures. arXiv admin note: substantial text overlap with arXiv:1109.339

Structure and properties of Ti/TiB metal-matrix composite after isothermal multiaxial forging

Microstructure and mechanical properties of a Ti/TiB metal-matrix composites after multiaxial forging at 850°C to the true strain " = 5:2 were studied. The composite with 17 vol.% of TiB was produced via spark plasma sintering at 1000°

Kinetics of grain refinemet in metallic materials during large strain deformation

The development of ultrafine grained microstructures in austenitic stainless steel and pure titanium subjected to large strain deformation was comparatively studied. The change in the volume fractions of newly developed ultrafine grains was used to quantify the progress in grain refinement during plastic deformatio

Improving the spatial resolution by effective subtraction technique at Irkutsk incoherent scatter radar: the theory and experiment

We describe a sounding technique that allows us to improve spatial resolution of Irkutsk Incoherent Scatter Radar without loosing spectral resolution. The technique is based on transmitting of rectangle pulses of different duration in various sounding runs and subtracting correlation matrixes. Theoretically and experimentally we have shown, that subtraction of the mean-square parameters of the scattered signal for different kinds of the sounding signal one from another allows us to solve the problem within the framework of quasi-static ionospheric parameters approximation.Comment: 4 pages, 3 figures, to appear at URSI-2011 conferenc

Microstructure evolution of commercial-purity titanium during cryorolling

Electron backscatter diffraction and transmission electron microscopy have been used to analyze the microstructural evolution of titanium during rolling at a cryogenic temperature (T = –196°C). It has been found that intensive twinning at the cryogenic deformation temperature accelerates the kinetics of micro structure refinement. The quantitative analysis of microstructure evolution in titanium upon cryorolling has shown that structure evolution is mainly related to mechanical twinning in the initial stages cryorolling is discusse