Introduction: The Stardust mission obtained the first dust samples in the coma of an active comet for laboratory analyses. Earlier chemical data on dust from an active comet came from the GIOTTO and VEGA missions to comet Halley [1]. For decades aggregate interplanetary dust particles (IDPs) were available from parent bodies other than those of meteorites [2], i.e. comets or comet-like bodies. ...

Mechanism of fatigue crack initiation was investigated in ultrafine-grained (UFG) magnesium alloy AZ91 processed by equal channel angular pressing (ECAP). Fatigue behaviour of UFG material was compared to the behaviour of material in an initial as-cast state. Focused ion beam technique (FIB) was applied to reveal the surface relief and early fatigue cracks. Two substantially different mechanism...

Field ion microscopy and computer simulation were used for the study of an atomic structure high-angle grain boundary in hard-drawn ultrafine-grained tungsten wire. These boundaries with special misorientations are beyond the scope of the coincident site lattice model. It was demonstrated that the special non-coincident grain boundaries are the plane-matching boundaries, and rigid-body displace...

We present the results of in-situ studies of evolution of grain boundary misorientations in ultrafine grained (UFG) aluminum alloy Al-4 Cu-0.5 Zr (wt%) during annealing. The structure of the UFG alloy was obtained by severe plastic deformation method. Misorientations between the grains were measured using single reflection technique. It was found that relaxation processes during annealing are a...

V.A. Andreyachshenko, Faculty of Nanotechnology and Metallurgy, Karaganda state technical University, Karaganda, Kazakhstan A.B. Naizabekov, Mining and Metallurgy Faculty, Rudny Industrial Institute, Rudny, Kazakhstan In the present research, equal channel angular pressing (ECAP) was conducted. The defectness degree of the alloy for one pass and maximum strain was determined. Ultra fine grained...

Ambient and cryogenic surface mechanical attrition treatments (SMAT) are applied to bcc iron plate. Both processes result in significant surface grain refinement down to the ultrafine-grained regime; the cryogenic treatment results in a 45% greater grain size reduction. However, the refined region is shallower in the cryogenic SMAT process. The tensile ductility of the grain size gradient remai...

Generally, AZ31 magnesium alloys have poor formation ability near room temperature. This material, with ultrafine grains, usually exhibits excellent superplasticity at high Therefore, the preparation of materials suitable microstructures to obtain is an important goal. In this study, double-side FSW (Friction Stir Processing) process was applied on AZ31Mg alloy microstructure ultra-fine grains....

Abstract This research paper mainly studied the microstructure and hardness of weld bead welding heat affected zone ultrafine grain steel after CO 2 gas-shielded welding. After normalizing quenching treatment, changes in welded joints were studied. These experimental results showed that joint was dendritic. The a mixed structure proeutectoid ferrite, side plate bainite, pearlite. overheated HAZ...

In many cases, due to high surface stress, stress concentration and wear, the metal material starts fail from surface. It is necessary investigate interface evolution characteristics under high-speed collisions for widely used materials. The microstructures strengthening mechanism of Ni balls after with 316 L stainless steel were investigated by a self-designed test system. was found that ultra...

Effects of the filament diameter on the microstructure and the critical current density (J ) were investigated in the external diffusion processed multififamentary Nb Sn-Cu superconducting composites. J was measured in transvere magnetic fields(H) of 10-17 Tesla. The mi~rostructures were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) after each step...