S. Yu. Mironov

Severe cryogenic deformation of copper

The method of automated analysis of electron backscatter diffraction (EBSD) patterns has been employed for the characterization of the structure of copper obtained using severe plastic deformation by shear under high pressure under cryogenic conditions. It has been established that severe cryogenic deformation leads to a considerable refinement of the structure to a grain size of 0.2 μm. Based on an analysis of the texture data and misorientation spectrum, it has been concluded that it is the 111<110> dislocation slip that was the main mechanism of plastic flow and that the contribution from twinning was very small. It has been shown that the evolution of the grain structure was mainly determined by elongation of initial grains in the direction of macroscopic shear and their subsequent fragmentation.

Formation of Grain Boundary Misorientation Spectrum in Alpha-Beta Titanium Alloys with Lamellar Structure under Warm and Hot Working

Microstructure evolution in alpha-beta Ti-64 alloy samples with lamellar structure deformed to a height reduction of 70% at temperatures between 450 and 800°C has been investigated. The deformation led to a distinctly globularized structure of α- and β-phase in the whole temperature interval. The dependence of globular grain size on deformation temperature is of a linear character up to the temperature of warm deformation at which formation of an SMC structure takes place. Continuous recrystallization was observed in the α-and β-phases. Different types of defects responsible for splitting of α-lamellae such as low and high angle boundaries, shear bands and twins were found. An investigation of boundary misorientation spectra in the α-and β-phases deformed to different strains at 550 and 800°C was carried out. Typical boundary misorientation spectra for single phase metals with the same lattice were obtained. The boundary misorientation spectrum depends weakly on strain and deformation temperature. The results of this study show the importance of transformation of semi-coherent interphase boundaries to non-coherent ones for globularization of lamellar microstructures.

Disk Yb:KGW amplifier of profiled pulses of laser driver for electron photoinjector.

We investigated a diode-pumped multipass disk Yb:KGW amplifier intended for amplifying a train of 3D ellipsoidal pulses of a laser driver for a photocathode of a linear electron accelerator. The multipass amplification geometry permitted increasing the energy of broadband (about 10 nm) pulses with a repetition rate of 1 MHz from 0.12 µJ to 39 µJ, despite large losses (two orders of magnitude) introduced by a beam shaper of 3D ellipsoidal beam. The distortions of the pulse train envelope were minimal due to optimal delay between the moment of pump switching on and arrival of the first pulse of the train.

Effect of low-temperature rolling on the structure of copper

The influence of rolling at a liquid-nitrogen temperature on the microstructure of commercially pure copper has been investigated by the methods of transmission electron microscopy (TEM) and automated analysis of electron backscatter diffraction (EBSD) patterns. It has been established that the process of the structure formation was sufficiently complex and included a geometric effect of deformation, recrystallization, twinning, and fragmentation. It is shown that upon deformation to 50% the structure evolution was controlled by the Taylor-Polanyi principle. However, it was established that at larger reductions the formation of grain structure was determined by the competition between the geometric effect of deformation and recrystallization. The contribution of twinning and fragmentation to the structure formation was insignificant in the entire interval of deformations investigated. The recrystallization, apparently, was caused by the warming up of the sample to room temperature after low-temperature rolling.

Evolution of dislocation boundaries during cold deformation of microcrystalline titanium

AbstractThe evolution of the misorientation spectrum of titanium during cold deformation via uniaxial tension was analyzed. The initial stage of plastic flow (true strain e ∼ 0.1) is characterized by the intense formation of low-angle boundaries (LABs). The axes of rotation of most LABs are close to 〈001〉. This fact can be treated as a consequence of predominant prismatic slip during plastic deformation of titanium. An increase in strain to e ∼ 0.5 and ∼ 1.0 is accompanied by both a gradual increase in the mean misorientation angle of LABs and an increase in the fraction of high-angle boundaries (HABs). Twinning occurs over the entire deformation range under study: twinning on the {112}〈

On the Mechanism of Deformation in Submicrocrystalline Titanium

\overline 1 \overline 1

Structural state and superplasticity of an aluminum-lithium alloy subjected to equal-channel-angular pressing

3〉 system is predominant at the initial stage, and twinning on the {102}〈