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The mechanical properties under uniaxial compression of cylindrical samples of ultrafine-grain (UFG) zirconium (grain size ∼0.4 μm) obtained by intense plastic strain (IPS)—a combination of extrusion, annealing, and drawing—have been studied in the temperature range 4.2–300 K. The mechanical characteristics of UFG zirconium have been studied in two structural states and the results are compared with each other as well as with the characteristics of coarse-grain polycrystals of this material (state 1—samples after IPS, state 2—samples after IPS and annealing). It has been established that grain-size reduction under IPS substantially increases the yield stress of polycrystals (by a factor of 6 at 300 K and by a factor of 4 at 77 K) while maintaining a large reserve of plasticity up to 15%. Two stages of strain hardening and a decrease of the plastic-flow activation volume with increasing strain has been recorded in the strain diagrams of UFG zirconium. It is concluded that the main mechanisms determining the yield stress and strain hardening are the same for ultrafine- and coarse-grain zirconium: intragrain dislocation slip and twinning occur in parallel and interact with one another. [ABSTRACT FROM AUTHOR]

Field-ion microscopy and molecular dynamics simulation were used for the characterization of the translation states at special grain boundaries in tungsten. It is revealed that rigid-body displacement had the component of displacement parallel to the [110] direction equal to 0 or 1 interplanar spacing. Full vectors of lateral shifts are described by broad statistical distribution. The mathematical simulation revealed two mirror-symmetry-breaking lateral translations along the $[{\bar{2}21}]$ direction of the Σ9 grain boundary corresponding to different atomic structures. It is shown that the partial disconnection with the $(a/18)[{\bar{2}21}]$ Burgers vector can be considered as the elemental carriers of grain-boundary polymorphic transformation. [ABSTRACT FROM AUTHOR]

The electrical resistivity of icosahedral quasicrystals Ti41.5Zr41.5Ni17 is investigated in the temperature region between 0.3 and 300 K on samples of different quality. At temperatures between 0.3 and 2 K the influence of external magnetic fields up to 16 kOe on the superconducting transition of these materials is investigated. The temperature dependence of the resistivity in the region of the superconducting transition varies in a step-like manner. The data of the x-ray analysis imply the presence of several different quasicrystalline phases. Above the superconducting transition a resistivity minimum is observed. © 2005 American Institute of Physics. [ABSTRACT FROM AUTHOR]