W-2 wt.%Y2O3 composite: Microstructure and mechanical properties

A W-2Y(2)O(3) composite is produced by powder metallurgy, including the pressing of the mixed elemental powders, their sintering and hot forging. The microstructure of the obtained composite is investigated using light microscopy, scanning electron microscopy and transmission electron microscopy. It appears that the material is composed of W grains having a mean size of 1-2 mu m and Y2O3 particles having a mean size of 300 nm to 1 mu m. The W grains contain a high density of dislocations. The mechanical properties of this material are investigated using nanoindentation and 3-point bend test. Berkovich hardness value is found to be 4.9 GPa at 10 N load, which is similar to that of pure W. 3-Point bend test shows that the composite starts to show ductile behavior approximately at 400 degrees C and the bending stress continuously decreases from 200 degrees C to 1000 degrees C. (C) 2012 Elsevier B.V. All rights reserved

Magneto-transport studies in yttrium doped lanthanum manganites between 10-300K

443-447<span style="font-size: 16.0pt;mso-bidi-font-size:9.0pt;font-family:" times="" new="" roman","serif""="">The hole doped manganite systems A1-xAxMnO3 (where A represents lanthanides and A's are divalent cations) with x<span style="font-size: 13.5pt;mso-bidi-font-size:6.5pt;font-family:" times="" new="" roman","serif";="" mso-fareast-font-family:hiddenhorzocr"="">≤<span style="font-size:13.5pt; mso-bidi-font-size:6.5pt;font-family:HiddenHorzOCR;mso-hansi-font-family:" times="" new="" roman";="" mso-bidi-font-family:hiddenhorzocr"=""> <span style="font-size:16.0pt; mso-bidi-font-size:9.0pt;font-family:" times="" new="" roman","serif""="">0.45 exhibit the electronic transport behavior that results from the complex interplay  among charge carriers, spin and lattice. The system shows a metal-insulator transition and the transition temperature (TMI) is strongly dependent on various factors, viz, dopant, thermal history, oxygen content grain size etc. Large magneto-resistance observed <span style="font-size: 16.0pt;mso-bidi-font-size:9.0pt;font-family:" times="" new="" roman","serif""="">near TMI in these perovskites is another interesting feature that has enormous implications in device and sensor technology. In the present paper, we report our results on the temperature dependence of the electrical resistivity on a set of samples of the type La<span style="font-size:12.5pt;mso-bidi-font-size:5.5pt; font-family:" arial","sans-serif""="">0.6<span style="font-size:16.0pt; mso-bidi-font-size:9.0pt;font-family:" times="" new="" roman","serif""="">Y0.07Ca0.33MnO3, prepared by a new pyrophoric technique. Our analysis confirms <span style="font-size: 16.0pt;mso-bidi-font-size:9.0pt;font-family:" times="" new="" roman","serif""="">adiabatic small polaron hopping forT> T<span style="font-size:12.0pt; mso-bidi-font-size:5.0pt;font-family:" times="" new="" roman","serif""="">MI while, in the metallic region (T <span style="font-size:12.0pt; mso-bidi-font-size:5.0pt;font-family:" times="" new="" roman","serif""="">M1), electron-electron and electronmagnon scattering play the dominant role in defining the influence of annealing time on <span style="font-size:16.5pt;mso-bidi-font-size: 9.5pt;font-family:" times="" new="" roman","serif""="">the electrical resistivity of fine grained polycrystalline La<span style="font-size:12.5pt; mso-bidi-font-size:5.5pt;font-family:" arial","sans-serif""="">0.6Y0.07Ca0.33MnO3 pellets. </span

Microstructure and mechanical properties of a W-2wt.%Y2O3 composite produced by sintering and hot forging

A W-2Y(2)O(3) composite has been developed by powder metallurgy methods in collaboration with the Plansee Company (Austria). The microstructure of the composite was analyzed using transmission electron microscopy and electron backscatter diffraction in scanning electron microscopy. The mechanical properties of the composite were analyzed using nano-indentation experiments, tensile and Charpy impact tests. It was mainly found that the composite exhibits ductile tensile behavior at 673-1273 K but weak Charpy impact properties, characterized by low absorbed energy values, at 773-1273 K. (C) 2013 Elsevier B.V. All rights reserved

Investigation of microstructure and mechanical properties of W-Y and W-Y2O3 materials fabricated by powder metallurgy method

W-2Y, W-1Y(2)O(3) and W-2Y(2)O(3) materials have been fabricated using two different powder metallurgy methods. While W-2Y and W-1Y(2)O(3) have been fabricated using mechanical alloying and hot isostatic pressing (Hipping), W-2Y(2)O(3) has been fabricated by sintering and hot forging method. Transmission electron microscopy observation reveals that W-2Y and W-1Y(2)O(3) materials have nano-structured grains whereas W-2Y(2)O(3) material has pm size grains. In both cases, the particles are distributed in homogeneously inside the grains. Berkovich hardness and 3 point bend tests confirm that in-spite of nano-structured grains, W-2Y, and W-1Y(2)O(3) materials are highly stiff and show no ductility till 1000 degrees C temperature range. In the case of W-2Y(2)O(3), the Berkovich hardness value is found to be 4.9 GPa, that is similar to the Berkovich hardness value of pure Wand 3-point bend test confirms that W-2Y(2)O(3) is ductile at 400 degrees C and above. Relation between the fabrication techniques, the microstructures and mechanical properties in W-2Y, W-1Y(2)O(3) and W-2Y(2)O(3) materials is reported. (C) 2015 Elsevier Ltd. All rights reserved

Investigation of microstructure and microhardness of pure W and W-2Y(2)O(3) materials before and after ion-irradiation

Pure W and W-2Y(2)O(3) materials were fabricated using powder metallurgy method. The microstructures of the materials were investigated by electron back-scattered diffraction and transmission electron microscopy techniques. Both materials contain 1-2 mu m size W grains. In the case of W-2Y(2)O(3), the material contains yttria particles having sizes between 300 and 900 nm. The W matrix in W-2Y(2)O(3) shows stronger texture than that of pure W. Berkovich hardness values are 4.5 GPa in pure W and 4.9 GPa in W-2Y(2)O(3) for a 10 N load. Ion irradiation experiments were performed on both materials at the JANNuS facility (Saclay, France) using Fe and He ions with energies of 24 MeV and 2 MeV, respectively. Radiation loops are present on the W grains whereas on yttria particles, radiation-induced damages appear as voids. Berkovich hardness values of irradiated materials are slightly higher than the non-irradiated materials. Results of the microstructure and microhardness of irradiated as well as non-irradiated materials are presented in detail. (C) 2014 Elsevier Ltd. All rights reserved

Effect of Annealing on Microstructural Development and Grain Orientation in electrodeposited Ni

Thick (up to 5 mm) Ni electrodeposits were produced by the pulsed electrodeposition (PED) technique. The PED-Ni was investigated in planar and cross-sections using high resolution scanning electron microscopy. Grain size and local texture were studied by electron backscatter diffraction. Thermal stability and grain growth behaviour were investigated using in-situ annealing in the transmission electron microscope. It is observed that columnar grains are present in the material and that the orientation of grains is not uniform. Textures and in-situ annealing behaviour are compared to previous data on nanocrystalline PED-Ni and Ni-Fe, where a subgrain coalescence model adopted from recrystallization is used to describe the occurrence of abnormal grain growth upon annealing and where twinning was found to be responsible for the texture development

Recent Progress in R&D on Tungsten Alloys for Divertor Structural and Plasma Facing Materials

Tungsten materials are candidates for plasma-facing components for the International Thermonuclear Experimental Reactor and the DEMOnstration power plant because of their superior thermophysical properties. Because these materials are not common structural materials like steels, knowledge and strategies to improve the properties are still under development. These strategies discussed here, include new alloying approaches and microstructural stabilization by oxide dispersion strengthened as well as TiC stabilized tungsten based materials. The fracture behavior is improved by using tungsten laminated and tungsten wire reinforced materials. Material development is accompanied by neutron irradiation campaigns. Self-passivation, which is essential in case of loss-of-coolant accidents for plasma facing materials, can be achieved by certain amounts of chromium and titanium. Furthermore, modeling and computer simulation on the influence of alloying elements and heat loading and helium bombardment will be presented

A brief summary of the progress on the EFDA tungsten materials program

The long-term objective of the European Fusion Development Agreement (EFDA) fusion materials programme is to develop structural and armor materials in combination with the necessary production and fabrication technologies for reactor concepts beyond the International Thermonuclear Experimental Reactor. The programmatic roadmap is structured into four engineering research lines which comprise fabrication process development, structural material development, armor material optimization, and irradiation performance testing, which are complemented by a fundamental research programme on "Materials Science and Modeling." This paper presents the current research status of the EFDA experimental and testing investigations, and gives a detailed overview of the latest results on materials research, fabrication, joining, high heat flux testing, plasticity studies, modeling, and validation experiments. © 2013 Elsevier B.V. All rights reserved