Phase Composition and Defect Substructure of Strengthening Layer Surfaced on Low Alloyed Steel

The microstructure and microhardness distribution in surface of low carbon Hardox 450 steel coated with alloyed powder wires of different chemical compositions are studied. It is shown that the microhardness of 6-8 mm thickness surfaced layer exceeds that of base metal by more than 2 times. The increased mechanical properties of surfaced layer are caused by the submicro and nanoscale dispersed martensite, containing the niobium carbides Nb2C, NbC and iron borides Fe2B. In the bulk plates a dislocation substructure of the net-like type with scalar islocation density of 10^11 cm^-2 is observed. The layer surfaced with the wire containing B possesses the highest hardness. The possible mechanisms of niobium and boron carbides formation in surfacing are discusse

Inverse Bifurcation Problem as a Tool For Rapid Identification of Progressive Collapse for Thin-Walled Systems

Notwithstanding recent advances in robust design, the problem of vulnerability of structures is still open. On the one hand, this leads to various structure collapses; on the other hand, this prompts researchers to develop models and methods to identify a state o f progressive collapse and estimate lifetime and residual functionality of perturbed structure. An inverse bifurcation problem implies that one identifies a pre-bifurcation state of a perturbed thin-walled system. The topological precursor (a tool to solve an inverse bifurcation problem) used is based on typical sequences o f deformed states extracted from clustered post-critical solutions o f non-linear boundary problem o f thin-walled systems theory. It implies that complete bifurcation structure o f the non-linear boundary problem (including primary, secondary and tertiary bifurcation paths) are constructed. The proposed approach was employed to identify a pre-bifurcation state of a cylindrical shell under uniform pressure (close to the critical) subjected to a pulse impact

Orientation of nickel-based alloy after thermal treatment

The paper presents transmission electron microscopy investigations of Ni-Al-Co alloy with γ′- and γ -phases obtained by directional crystallization. The main alloying elements are Cr, Ta, and Re in the amount of no more than 3.5 аt % each. W and Mo are present in a smaller amount. The alloy structure is investigated in two states: (1) original (after directional crystallization and long-term homogenezation which includes a series of annealing ranging from 1285 to 1340°С) and (2) original state subjected to subsequent annealing within 900–1000°С temperature range during 105–1143 h. The experiments show that the annealing process causes the fracture of the ideal quasi-cuboid structure of the γ′-phase and modifies its preferable orientation. The increase in the annealing temperature modifies the morphology of the γ′-phase that, in turn, changes the grain orientation in the alloy

The first molecular phylogeny of Buthidae (Scorpiones)

The first partial phylogeny of family Buthidae (17 genera) is presented, based on molecular data (16S rRNA mitochondrial DNA). The strong support for a monophyletic Old World group of 13 genera (mainly Palearctic desert forms) is demonstrated, while representative genera from Madagascar (Grosphus) and Southeast Asia (Lychas) group outside, as well as New World genera Centruroides and Rhopalurus. A very strong support is observed for the first time for three groups of Old World genera: (a) Compsobuthus, Mesobuthus, Liobuthus, Kraepelinia; (b) Hottentotta, Buthacus; (c) Orthochirus, Anomalobuthus. Phylogenetic hypotheses are discussed

The first molecular phylogeny of Buthidae (Scorpiones)

The first partial phylogeny of family Buthidae (17 genera) is presented, based on molecular data (16S rRNA mitochondrial DNA). The strong support for a monophyletic Old World group of 13 genera (mainly Palearctic desert forms) is demonstrated, while representative genera from Madagascar (Grosphus) and Southeast Asia (Lychas) group outside, as well as New World genera Centruroides and Rhopalurus. A very strong support is observed for the first time for three groups of Old World genera: (a) Compsobuthus, Mesobuthus, Liobuthus, Kraepelinia; (b) Hottentotta, Buthacus; (c) Orthochirus, Anomalobuthus. Phylogenetic hypotheses are discussed

Pulsating Strings in Deformed Backgrounds

This is a brief summary on pulsating strings in beta deformed backgrounds found recently.Comment: 8 pages. Talk presented at Quantum Theory and Symmetries 7, Prague, August 7-13, 201

Morphology of the surface of technically pure titanium VT1-0 after electroexplosive carbonization with a weighed zirconium oxide powder sample and electron beam treatment

Titanium is carbonized by the electroexplosive method. Formation of a surface alloyed layer and a coating on the treated surface is established by the methods of transmission electron microscopy. The morphology and elemental composition of the alloyed layer are analyzed. A dependence of the structure of the modified layer subjected to electron gun treatment on the absorbed power density is revealed

Pulsating Strings in Lunin-Maldacena Backgrounds

We consider pulsating strings in Lunin-Maldacena backgrounds, specifically in deformed Minkowski spacetime and deformed AdS_5xS^5. We find the relation between the energy and the oscillation number of the pulsating string when the deformation is small. Since the oscillation number is an adiabatic invariant it can be used to explore the regime of highly excited string states. We then quantize the string and look for such a sector. For the deformed Minkowski background we find a precise match with the classical results if the oscillation number is quantized as an even number. For the deformed AdS_5xS^5 we find a contribution which depends on the deformation parameter.Comment: 16 pages, 2 figures, typos fixe

Structural Phase Transformation of Rail Steel in Compression

The analysis of structure and defective substructure of rail steel in uniaxial compression to a degree of 50% is carried out. It is revealed that cold hardening has a multi-stage character and is accompanied by fragmentations of pearlite grains which is in field as the degree of deformation increases and reaches ≈ 0.4 volume of the foil studied at ε = 50%. The fragments being formed in ferrite plates are separated by low-angle boundaries. The average size of the fragmented ferrite decreases from 240 nm at ε = 15% to 200 nm at ε = 50%. Concurrently with the ferrite fragmentation, fragments of cementite are also observed. It is found that the sizes of the cementite fragments are in a range of 15 to 20 nm and depend weakly on the degree of sample deformation. The cementite fragmentation is caused by deformation-induced carbon dissolution and dislocation-induced fracture. The carbon atoms diffuse from cementite crystal to dislocations, which move through an interplanar space to form particles of tertiary cementite at nanoscale (2–4 nm). It is found that the increase in the degree of deformation is accompanied by a decrease in the scalar and an excess dislocation density. A physical interpretation of the observations has been given