Fracture toughness of two Cr2Hf+Cr intermetallic composites as a function temperature

Journal ArticleFracture toughness as a function of temperature was evaluated for two Cr2Hf+Cr intermetallic composites, each in two different microstructural conditions. The proeutectic microstructures based on Cr-6.5Hf (at%) showed a significant increase in fracture toughness with an increase from room temperature to 600°C

The chemically ordered glass: the limiting composition for chemical order in amorphous packings of hard-sphere mixtures

We consider the limits of chemical order (i.e. avoidance of solute-solute contact) in amorphous close-packed mixtures of hard spheres of two different sizes. The upper bound on the solute concentration, beyond which solute-solute contact cannot be avoided, is determined for a range of particle size ratios. Scaling the composition by this limiting value is found to collapse plots of the solute coordination and mixture energies as a function of composition for different values of size ratios onto a single master curve. A number of features of the behaviour of amorphous alloys in the vicinity of this limiting concentration are discussed.Fil: Harrowell, Peter. University of Sydney; AustraliaFil: Fernandez, Julian Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Miracle, D. B.. Wright-Patterson Air Force Base; Estados Unido

Penyelenggaraan Urusan Pemerintahan Daerah Berciri Kepulauan (Kajian Terhadap Pelayanan Administrasi Kependudukan di Kabupaten Maluku Tengah)

Masalah pelayanan administrasi kependudukan di wilayah bercirikan kepulauan seperti di Kabupaten Maluku tengah, menjadikan masyarakat kesulitan untuk mendapatkan layanan pengurusan administrasi kependudukan seperti pengurusan KTP dan administrasi kependudukan lainnya. Tujuan penelitian ini adalah untuk melakukan analisis terhadap penyelenggaraan pemerintahan dalam pelayanan administrasi kependudukan di daerah yang berciri kepulauan. Metode penelitian adalah penelitian hukum normative. Hasil penelitian menunjukkan bahwa penyelenggaraan pemerintahan di kabupaten Maluku Tengah terkait pelayanan administrasi kependudukan masih terkendala karena pengurusan data kependudukan Masyarakat harus ke ibu kota kabupaten, karena wewenang kecamatan hanya sebatas perekaman data kependudukan. Pengurusan pencetakannya harus ke ibu kota kabupaten di kota masohi, yang jarak menuju ibu kota kabupaten sangat jauh sehingga untuk mendapatkan data administrasi kependudukan membutuhkan pembiayaan yang sangat besar. Perlu desain alternatif kebijakan yang dapat mendukung kelancaran penyelenggaraan pemerintahan di bidang pelayanan data administrasi kependudukan dengan cara melimpahkan kewenangan bagi kecamatan, pembentukan UPTD Disdukcapil di kecamatan, demi terwujudnya keserasian dan keseimbangan hubungan negara dan warga masyarakat

Crucial role of sidewalls in velocity distributions in quasi-2D granular gases

Our experiments and three-dimensional molecular dynamics simulations of particles confined to a vertical monolayer by closely spaced frictional walls (sidewalls) yield velocity distributions with non-Gaussian tails and a peak near zero velocity. Simulations with frictionless sidewalls are not peaked. Thus interactions between particles and their container are an important determinant of the shape of the distribution and should be considered when evaluating experiments on a tightly constrained monolayer of particles.Comment: 4 pages, 4 figures, Added reference, model explanation charified, other minor change

In situ visualization of Ni-Nb bulk metallic glasses phase transition

We report the results of the Ni-based bulk metallic glass structural evolution and crystallization behavior in situ investigation. The X-ray diffraction (XRD), transmission electron microscopy (TEM), nano-beam diffraction (NBD), differential scanning calorimetry (DSC), radial distribution function (RDF) and scanning probe microscopy/spectroscopy (STM/STS) techniques were applied to analyze the structure and electronic properties of Ni63.5Nb36.5 glasses before and after crystallization. It was proved that partial surface crystallization of Ni63.5Nb36.5 can occur at the temperature lower than for the full sample crystallization. According to our STM measurements the primary crystallization is originally starting with the Ni3Nb phase formation. It was shown that surface crystallization drastically differs from the bulk crystallization due to the possible surface reconstruction. The mechanism of Ni63.5Nb36.5 glass alloy 2D-crystallization was suggested, which corresponds to the local metastable (3x3)-Ni(111) surface phase formation. The possibility of different surface nano-structures development by the annealing of the originally glassy alloy in ultra high vacuum at the temperature lower, than the crystallization temperature was shown. The increase of mean square surface roughness parameter Rq while moving from glassy to fully crystallized state can be caused by concurrent growth of Ni3Nb and Ni6Nb7 bulk phases. The simple empirical model for the estimation of Ni63.5Nb36.5 cluster size was suggested, and the obtained values (7.64 A, 8.08 A) are in good agreement with STM measurements data (8 A-10 A)

Implementación de biodigestores familiares en el Perú. Experiencias de Yanaoca (Cusco) y Ventanilla (Lima)

Peer ReviewedPostprint (published version

Abstract polymer models with general pair interactions

A convergence criterion of cluster expansion is presented in the case of an abstract polymer system with general pair interactions (i.e. not necessarily hard core or repulsive). As a concrete example, the low temperature disordered phase of the BEG model with infinite range interactions, decaying polynomially as $1/r^{d+\lambda}$ with $\lambda>0$, is studied.Comment: 19 pages. Corrected statement for the stability condition (2.3) and modified section 3.1 of the proof of theorem 1 consistently with (2.3). Added a reference and modified a sentence at the end of sec. 2.

Development of high temperature refractory-based multi-principle-component alloys by thermodynamic calculations and rapid alloy prototyping

Recently, new refractory-based high entropy alloys (HEAs) have been investigated for potential use as high temperature structural alloys, and some alloys exhibit excellent high temperature strength and ductility. While the high entropy alloy community is generally concerned with obtaining single phase solid-solution phases, secondary strengthening phases are usually required to achieve an adequate balance of mechanical and physical properties for structural applications. This contribution will report on new Mo,Nb-based alloys that have been developed using HEA design guidelines, as well as new tools that enable thermodynamic property predictions and rapid alloy prototyping and assessment. An elemental palette of Mo-Nb-Hf-Ta-Ti-V-W-Zr was chosen in order to promote the formation of a single body-centered cubic (BCC) solid-solution phase upon solidification, which facilitates homogenization heat treatments. Al, Cr, and Si were also included to promote secondary phase formation. These 11 elements were then used to calculate the phases present and their reaction temperatures of 3-, 4-, 5-, and 6-component alloy compositions from all of the available PandatTM databases. Mo and Nb were required to be present in each alloy composition in order to maintain modest alloy costs and densities. Please click Additional Files below to see the full abstract