Joint hydrogen susceptibility of 304 SS welded with titanium

Welds of thick plates (304 SS) clad with Ti of commercial purity in as-received state and also after subsequent heat treatment and/or after hydrogen charging were investigated. Fatigue tests were carried out at amplitude of 20 Hz and in case of bimetal without hydrogen charging also at amplitude of 40 Hz. After heat treatment, charged welds showed higher threshold level than the welds without heat treatment. Energy dispersed analyses (EDA) of fracture surfaces showed that failure predominantly occurred in joint. Hydrogen induced cracking (HIC) response of bimetal samples demonstrated favourable results both after welding and after subsequent heat treatment. Short and thin cracks were observed, exclusively located in mixed zone, where approx. 16-20 at. % of Ti using EDX (energy dispersed analyser) was revealed. By application of monochromatic synchrotron radiation Ti- , Fe-fcc, Fe-bcc and intermetallic phase Fe2Ti were detected.Web of Science5941610160

Phase analysis of explosive welded Ti-Cr/Ni steel in AS-received state and after heat treatment using synchrotron

Surface coatings protection is one of the most important processes ensuring efficient and economic use of basic materials, mostly of lower-quality. At interface of clad and basic material intermetallic phases are formed, representing quite different matrix with dissimilar properties unlike the welded materials. One type of surface coating is explosive bonding which belongs to group of pressure welding. The work is focused on interface shape line, inhomogeneities in vicinity of the wave joint both in basic material and in vicinity of weld line of the Ti and Cr/Ni stainless steel (SS) matrix. Investigated weld was both in as-received state and after heat treatment carried out at 600 C/90 minutes/air. Presented phases have been identified using X-ray diffraction performed by synchrotron. The Ti , Fe-fcc, Fe-bcc and intermetallic phases Fe2Ti were detected at interface area.Web of Science5941614161

Structure and mechanical properties of explosive welded Mg/Al bimetal

In the article we analyzed shape, local mechanical properties, chemical and phase composition of Magnesium/Aluminium cladded material prepared by explosion welding. In particular we focus our investigation on Mg/Al interface and areas close to the joint. Hardness of the joined materials measured far from their interface is similar for both materials, however in the region of interface the hardness drops down by 40%. Phase transformations in the interface was examined by a hard X-ray micro-diffraction experiment performed at beamline P07 at PETRA III at the energy of 99 keV which helped us identify in Al: fcc-Al, Al2Cu tetragonal and Al7Cu2Fe tetragonal and in Mg: hcp-Mg, Mg2Si cubic phases. In the interface we haven’t observed any new intermetallics, but computation of lattice parameters and profiles of Al and Mg peaks proved an existence of solid solution with different gradient of chemical composition.Web of Science5941597159

Lattices, MEbius Functions and Communication Complexity

Abstract. In a recent paper, Hajnal, Maass and Tura'n analyzed the communication complexity of graph connectivity. Building on this work, we develop a general framework for the study of a broad class of communication problems which has several interesting special cases including the graph connectivity problem. The approach is based on combinatorial lattice theory. LINTRODUCTION Communication complexity is concerned with the question: how much information do two processors need to exchange to compute a specified function fthat depends on both of their inputs? The minimum number of bits that must be communicated is the deterministic communicaiion complexity off. Set Disjointness. Each processor is given a set (from a finite universe X of size n ) and they must determine whether the sets are disjoint. Trivially n bits of communication suffice: one processor tells the other the incidence vector of its subset. There is also a simple information theoretic lower bound of logn. It has in fact been shown that the upper bound is tight. Natural variants of this problem arise in a number of settings: Convex Sei Disjointness. The universe X is a finite subset of Euclidean d-space. Each processor is given a finite subset of X and they must determine whether the intersection of their convex hulls contains a point from X. Vector Disjoinmess. The universe X is a finite set of vectors from some vector space. Each processor is given a subset of X and they must determine whether the intersection of the subspaces spanned by each set contains a common vector from X. Tree Disjointness. Each processor is given a subtree of a fixed tree on vertex set X and they must determine whether the trees have a vertex in common. Other problems with a similar flavor include: Each processor is given a graph on vertex set V and they must determine if the union of the graphs is connected. Graph (s.t)-Connectivity. Each processor is given a graph on vertex set V and they must determine if the union has a path from s to t. Vector Space Span. Each processor is given a set of vectors (from a finite set of vectors X ) and they must determine whether the union of their sets spans the whole space. For each of these problems one can establish trivial upper and lower bounds on their communication complexity. Recently, Hajnal et al. [HMT] showed that the trivial upper bound on the graph connectivity problem is tight. As we will see, the trivial upper bound is also tight for the Znd, 5* and 6* problems, while for the other two there are protocols that come very close to the lower bound. In this paper, we define and investigate a broad class of communication problems that include all of the above as special cases. The natural setting for studying these problems is the combinatorial theory of alignments. A family L of subsets of X is an alignment if whenever A,B are contained in L then so is their intersection. For an alignment L, we consider: Disjointness Problem for L. Each processor gets a set from L and they must determine whether the sets are disjoint. It is not hard to see that the three variants of set 0272-5428/88/0000/0081.$01.00 0 1988 IEEE 8

High-pressure x-ray diffraction of icosahedral Zr-Al-Ni-Cu-Ag quasicrystals

The effect of pressure on the structural stability of icosahedral Zr-Al-Ni-Cu-Ag quasicrystals forming from a Zr65Al7.5Ni10Cu7.5Ag10 metallic glass with a supercooled liquid region of 44 K has been investigated by in situ high-pressure angle-dispersive x-ray powder diffraction at ambient temperature using synchrotron radiation. The icosahedral quasicrystal structure is retained up to the highest hydrostatic pressure used (approximately 28 GPa) and is reversible after decompression. The bulk modulus at zero pressure and its pressure derivative of the icosahedral Zr-Al-Ni-Cu-Ag quasicrystal are 99.10+/-1.26 GPa and 4.25+/-0.16, respectively. The compression behavior of different Bragg peaks is isotropic and the full width at half maximum of each peak remains almost unchanged during compression, indicating no anisotropic elasticity and no defects in the icosahedral Zr-Al-Ni-Cu-Ag quasicrystals induced by pressure

Lowest-energy structures of 13-atom binary clusters: Do icosahedral clusters exist in binary liquid alloys?

Although the existence of 13-atom icosahedral clusters in one-component close-packed undercooled liquids was predicted more than half a century ago by Frank, the existence of such icosahedral clusters is less clear in liquid alloys. We study the lowest-energy structures of 13-atom AxB13-x Lennard-Jones binary clusters using the modified space-fixed genetic algorithm and the artificial Lennard-Jones potential designed by Kob and Andersen. Curiously, the lowest-energy structures are non-icosahedral for almost all compositions. The role played by the icosahedral cluster in a binary glass is questionable.Comment: 10 pages, 3 figure (conference paper of LAM12) to be published in J. Non-Crystalline Solid