Diphoton excess and VV-scattering

We consider minimal effective interactions of the 750 GeV mass resonance observed recently by ATLAS and CMS. Assuming a new scalar and gauge invariant effective interactions leads to nontrivial two-particle scattering amplitudes with asymptotic gauge boson states. The longitudinally polarized W± and Z bosons interacting via dimension-five effective operators provide stringent constraints on the validity of the effective model. The large width found by ATLAS implying a bound of approximately 500 GeV already below the resonance, turns this scenario unlikely. For production mainly in gluon fusion, we get an upper bound of ∼ 1.3 TeV and strong limits on the masses of the underlying vector-like fermions are given. © 2016 World Scientific Publishing Company

Depth-sensing indentation tests in studying plastic instabilities

This review surveys the phenomenon of plastic instabilities occurring in depth-sensing indentation measurements. Investigations presented focus on the characterization of Portevin-Le Chatelier type instabilities observed in different metal alloys during indentation. The effect of some important factors such as solute concentration, the formation of Guinier-Preston zones, and grain size and orientation are described and discussed. The phenomenon of plastic instabilities as serrated flow recently observed in bulk metallic glasses is also briefly reviewed

A new method for hardness determination from depth sensing indentation tests

A new semiempirical formula is developed for the hardness determination of the materials from depth sensing indentation tests. The indentation works measured both during loading and unloading periods are used in the evaluation. The values of the Meyer hardness calculated in this way agree well with those obtained by conventional optical observation, where this latter is possible. While the new hardness formula characterizes well the behavior of the conventional hardness number even for the ideally elastic material, the mean contact pressure generally used in hardness determination differs significantly from the conventional hardness number when the ideally elastic limiting case is being approached

Sub-micrometre holotomographic characterisation of the effects of solution heat treatment on an AlMg7.3Si3.5 alloy

A strip cast AlMg7.3Si3.5 alloy is investigated by sub-micrometre holotomographic analysis achieving a voxel size of (60 nm)(3) by cone beam magnification of the focused synchrotron beam using Kirkpatrick-Baez mirrors. The three-dimensional microstructure of the same specimen volume in the as-cast state is compared with that after exposure to 540 degrees C for 30 min resolving microstructural features down to 180 nm. The three-dimensional analysis of the architecture of the eutectic Mg2Si and the Fe-aluminides reveals how the as-cast microstructure changes during the solution treatment. The alloy in the as-cast condition contains a highly interconnected seaweed-like Mg2Si eutectic. The level of three-dimensional interconnectivity of the Mg2Si eutectic phase decreases by only partial disintegration during the heat treatment correcting the two-dimensional metallographic impression of isolated round particles. Statistical analyses of the particle distribution, sphericity, mean curvatures and Gaussian curvatures describe quantitatively the architectural changes of the Mg2Si phase. This explains the decrease of the high temperature strength of the alloy by the solution treatment tested in hot compression. (C) 2012 Elsevier B.V. All rights reserved

Effect of solution heat treatment on the internal architecture and compressive strength of an AlMg4.7Si8 alloy

The evolution of the microstructure of an AlMg4.7Si8 alloy is investigated by scanning electron microscopy and ex situ synchrotron tomography in as-cast condition and subsequent solution treatments for 1 h and 25 h at 540 °C, respectively. The eutectic Mg2Si phase, which presents a highly interconnected structure in the as-cast condition, undergoes significant morphological changes during the solution heat treatment. Statistical analyses of the particle distribution, the sphericity, the mean curvatures and Gaussian curvatures describe the disintegration of the interconnected seaweed-like structure followed by the rounding of the disintegrated fractions of the eutectic branches quantitatively. The ternary eutectic Si resulting from the Si-surplus to the stoichiometric Mg2Si ratio of the alloy undergoes similar changes. The morphological evolution during solution heat treatment is correlated with results of elevated temperature compression tests at 300 °C. The elevated temperature compressive strength is more sensitive to the degree of interconnectivity of the three dimensional Mg2Si network than to the shape of the individual particles. © 2013 Elsevier B.V. All rights reserved