Defects in Friction Stir Welding of Steel

Defects associated with friction stir welding of two steel grades including DH36 and EH46 were investigated. Different welding parameters including tool rotational and tool traverse (linear) speeds were applied to understand their effect on weld seam defects including microcracks and voids formation. SEM images and infinite focus microscopy were employed to identify the defects types. Two new defects associated with the friction stir welding process are introduced in this work. The first defect identified in this work is a microcrack found between the plunge and the steady state region and attributed to the traverse moving of the tool with unsuitable speed from the plunge-dwell to the steady state stage. The tool traverse speed has recommended to travel 20 mm more with accelerated velocity range of 0.1 from the maximum traverse speed until reaching the steady state. The maximum recommended traverse speed in the steady state was also suggested to be less than 400 mm/min in order to avoid the lack in material flow. The second type of defect observed in this work was microcracks inside the stirred zone caused by elemental precipitations of TiN. The precipitates of TiN were attributed to the high tool rotational speed which caused the peak temperature to exceed 1200 °C at the top of the stirred zone and based on previous work. The limit of tool rotational speed was recommended to be maintained in the range of 200-500 RPM based on the mechanical experiments on the FSW samples

Thermo-Mechanical Effect on Poly Crystalline Boron Nitride Tool Life During Friction Stir Welding (Dwell Period)

Poly Crystalline Boron Nitride (PCBN) tool wear during the friction stir welding of high melting alloys is an obstacle to commercialize the process. This work simulates the friction stir welding process and tool wear during the plunge/dwell period of 14.8 mm EH46 thick plate steel. The Computational Fluid Dynamic (CFD) model was used for simulation and the wear of the tool is estimated from temperatures and shear stress profile on the tool surface. Two sets of tool rotational speeds were applied including 120 and 200 RPM. Seven plunge/dwell samples were prepared using PCBN FSW tool, six thermocouples were also embedded around each plunge/dwell case in order to record the temperatures during the welding process. Infinite focus microscopy technique was used to create macrographs for each case. The CFD result has been shown that a shear layer around the tool shoulder and probe-side denoted as thermo-mechanical affected zone (TMAZ) was formed and its size increase with tool rotational speed increase. Maximum peak temperature was also found to increase with tool rotational speed increase. PCBN tool wear under shoulder was found to increase with tool rotational speed increase as a result of tool’s binder softening after reaching to a peak temperature exceeds 1250 °C. Tool wear also found to increase at probe-side bottom as a result of high shear stress associated with the decrease in the tool rotational speed. The amount of BN particles revealed by SEM in the TMAZ were compared with the CFD model

Effect of (Sm, Co) co-doping on the structure and electrical conductivity of ZnO nanoparticles

(Sm, Co) co-doped ZnO nanoparticles (Zn _1−2x Sm _x Co _x O), $0.00\leqslant {\rm{x}}\leqslant 0.06,$ have been prepared by the co-precipitation technique. The effect of the dopant ions Sm ^3+ and Co ^2+ on the structural, morphological, and electrical conductivity of ZnO has been studied. XRD analysis shows the substitution of Zn ^2+ ions by the co-doping Sm ^3+ and Co ^2+ ions with the formation of secondary phases as Sm _2 O _3 and Co _3 O _4 upon 0.005 co-doping and above. Raman spectra showed the characteristic mode of the wurtzite structure of ZnO nanoparticles with a vibration assigned to the bound of Co with the donor defects at high doping level of (Sm, Co). The spherical morphology of pure ZnO is transformed into nanorods as the concentration of Sm ^3+ and Co ^2+ increases. From EDX spectra, it was shown that all samples exhibit an excellent compositional homogeneity that verifies the Sm and Co presence as real dopants in ZnO crystalline structure. FTIR spectra show one discrete peak at 417 cm ^−1 with another broad peak at 568 cm ^−1 corresponding to Zn–O stretching, which confirms the formation of the wurtzite structure of the samples. Photoluminescence studies reveal the existence of minor defects in the co-doped samples. The study proposes the suitable use of the samples in the high-efficiency UV light-emitting devices due to the intense UV peaks compared with the lower visible peaks. The excitation dependent PL spectra demonstrated a redshift with increasing the excitation wavelength accounting for the distribution of energetic species in the ground state. The DC electrical conductivity is enhanced with (Sm, Co) co-doping of x = 0.1 due to the formation of thermally activated donor levels

Preparation, characterization and DFT+U study of the polar Fe3+-based phase Ba5Fe2ZnIn4S15 containing S = 5/2 zigzag chains.

editorial reviewedThe polar magnetic chalcogenide phase Ba5Fe2ZnIn4S15 was synthesized and its structure was solved by single crystal XRD. It is the first member with a 3d magnetic metal (Fe3+) in the Pb5ZnGa6S15-type structure family of wide bandgap materials with non-linear optical properties. The three-dimensional framework possesses a low dimensional magnetic character through the presence of weakly interacting zig-zag chains made of corner-sharing FeS4 tetrahedra forming chain 1, [FeS2]-∞. The latter chains are separated by InS4 tetrahedra providing weak magnetic super-super exchanges between them. The framework is also constituted by chain 2, [In3Zn1S9]7-∞ (chain of T2-supertetrahedra) extended similarly to chain 1 along the direction c and connected through InS4 tetrahedra. Symmetry analysis shows that the intrinsic polarization observed in this class of materials is mostly due to the anionic framework. Preliminary magnetic measurements and density functional theory calculations suggest dominating antiferromagnetic interactions with strong super-exchange coupling within the Fe-chains

Mononeuropathie multiple dans le cadre d’une forme sévère d’infection par le virus H1N1

Introduction : Les atteintes neurologiques périphériques liées aux virus de la grippe saisonnière sont bien connues. Par contre durant la pandémie de la grippe A H1N1, les atteintes périphériques ont été très peu rapportées. Nous rapportons un cas d’atteinte périphérique plurifocale concomitante d’une infection sévère par le virus H1N1.Observation : Il s’agit d’une patiente de 42 ans hospitalisée pour une infection à grippe A H1N1 compliquée d’une pneumopathie hypoxémiante ayant nécessité un transfert en réanimation. A son réveil, il a été constaté une tétraparésie et une atteinte multiple des paires crâniennes. L’ENMG avait noté une mononévrite multiple axonale touchant aussi le nerf médian gauche, sans anomalies plus diffuses comme on l’aurait observé dans un processus inflammatoire démyélinisant. Il n’avait pas été documenté d’autre étiologie, notamment infectieuse, ni de carence vitaminique. L’étiologie infectieuse liée au virus H1N1 était donc la plus probable. Les différents contrôles ENMG à 3 et 9 mois ont noté qu’Il n’y avait plus d’atteinte neurogène très significative dans les muscles dépendant du médian.Discussion : bien que l’imputabilité de l’atteinte périphérique au virus H1N1 soit difficile, l’absence d’autres causes potentielles suggère que la neuropathie périphérique soit très probablement due au virus H1N1.Conclusion : Cette observation suggère que l’infection à H1N1 peut se compliquer d’atteintes neurologiques périphériques touchant même les paires crâniennes.Mots clés : H1N1, Mononeuropathie multiple, EMNG.English AbstractMononeuropathy multiplex in a severe h1n1 infection We present a case of a 42 years old woman who presents a mononeuropathy multiplex during severe acute H1N1 infection. She was admitted because of flu complicated of pneumopahy with hypoxemia. She was transfer in the intensive word. After intensive care she presents tetraparesia with cranial nerves attempt. The nerve conduction and the electromyography showed mononeuropathy multiplex of cranial nerves (left IX, X, XI and XII) and the left median. The H1N1 serology was positive. The study of the cerebral fluid was normal. The HIV, HBV and HBC serologies were negative. The Lyme disease test was negative. The control of nerve conduction and the electromyography at 3 and 9 month chow a good outcome. Even though it is difficult to attribute this mononeuropathy of the cranial nerves and the left median to the H1N1 infection, there was any other cause explaining this peripheral neuropathy. This case report suggests that mononeuropthy multiplex with cranial nerves attempt can complicate a H1N1 infectionKeywords: H1N1, mononeuropathy multiplex, electromyograph

Synthesis, Structure & Properties of CuBiSeCl2: A Chalcohalide Material with Low Thermal Conductivity

Mixed anion halide-chalcogenide materials have recently attracted attention for a variety of applications owing to their desirable optoelectronic properties. We report the synthesis of a previously unreported mixed-metal chalcohalide material, CuBiSeCl2 (Pnma), accessed through a simple, low temperature solid state route. The physical structure is characterized through Single Crystal X-Ray Diffraction and reveals significant Cu displacement within the CuSe2Cl4 octahedra. The electronic structure of CuBiSeCl2 is investigated computationally, which indicates highly anisotropic charge carrier effective masses, and by experimental verification using X-Ray Photoelectron Spectroscopy (XPS), which reveals a valence band dominated by Cu orbitals. The band gap is measured to be 1.40(3) eV, a suitable value for solar absorption applications. The electronic and thermal properties, including resistivity, Seebeck coefficient, thermal conductivity and heat capacity, are also measured and it is found that CuBiSeCl2 exhibits a low room temperature thermal conductivity of 0.27(4) W K-1 m-1