The effect of loading direction and Sn alloying on the deformation modes of Zr: An in-situ neutron diffraction study

Deformation modes (slip and twining) in a strongly textured model hcp alloy system (Zr–Sn) have been investigated using in-situ neutron diffraction and deformation along with complementary electron microscopy. Analysis of the evolution of the intergranular strain evolutions and intensity of specific reflections from neutron diffraction show differential influence of Sn on the extent of twinning too, depending on the deformation direction. While Sn displayed very noticeable influence on twin activity when samples were compressed along a direction that predominantly activates prismatic slip, this effect was not seen when samples were compressed along other different directions. These experimental observations were successfully simulated using a CPFE (crystal plasticity finite element) model that incorporates composition sensitive CRSS (critical resolved shear stress) for slip and composition insensitive CRSS activation of twinning. The success of the CPFE model in capturing the experimental observations with respect to twin evolution suggests that the twinning in Zr is chiefly governed by the initial crystallographic texture and the associated intergranular stress state generated during plastic deformation

Utilization Of IEC By Middle Level Health Personnel In The Implementation Of National Nutrition Programmes

Research question: Extent of utilization of the information, Education and Communication (IEC) components in the implementation of national nutrition programmes by middle level health personnel. Objectives: (i) To assess the knowledge of paramedics with regard to nutrition concepts and programmes and also (ii) to find out the current level of utilization of IEC inputs in the delivery of nutrition programmes. Study design: Cross- sectional, questionnaire survey. Setting: Regional Training Centres for Male and Female Health Workers located in the State of Andha Pradesh, India. Sample size: A total of 211 in â€" service trainees. Participants: Multipurpose Health Assistants (Male an Female), Multipurpose Health Supervisor (Male and Female) and Multipurpose Health Extension Officers. Study Variables: Socio- economic, health enhancing lifestyles, nutrition knowledge, mass media and small media utilization. Statistical analysis : Percent frequencies and mean scores with standard deviation, correlations. Results: Middle level health personnel scored well in nutrition knowledge. But their utilization of IEC tools in programme implementation and community education was not satisfactory. Use of print and broadcast media to update their nutrition knowledge was poor. A significant correlation was observed among variables like nutrition knowledge, mass media and small media utilization

High temperature and high pressure oxidation behavior of Zr-2.5Nb pressure tube material - Effect of beta phase composition and surface machining

Pressure tube material, Zr-2.5Nb, of pressurized heavy water reactors was given selective heat-treatments. The objective was to generate microstructures with different compositions of the second phase beta namely, Nb depleted beta(Zr) phase and Nb rich beta(Nb) phase. The material with bZr was then subjected to surface machining. The presence of phases after different heat-treatments was confirmed by X-ray diffraction and the resultant microstructures were characterized by transmission electron microscopy and electron back scattered diffraction. The Nb content in the beta phase after heat-treatments and residual stresses before and after surface machining were measured using X-ray diffraction. Oxidation was carried out in steam at 400 degrees C and 10 MPa up to 30 days and the oxides were characterized by Raman spectroscopy. It is shown that the presence of Nb rich beta(Nb) in the microstructure and faster diffusion of Nb into b phase brought about by surface machining resulted in an enhanced oxidation resistance. (C) 2015 Elsevier B.V. All rights reserved

Texture evolution in two phase Zr-2.5 wt-%Nb through modified route

Two phase Zr - 2(.)5 wt-%Nb is used as pressure tube material in water cooled and moderated reactors. The in service behaviour of this hcp zirconium based alloy is dependent on strong textures developed during thermomechanical processing. In the present study, the texture evolution during fabrication of this material, using a modified route, was investigated. Texture, evaluated by the orientation distribution function, was correlated to microstructure during various stages of processing. It was observed that a strong orientation fibre parallel to the working direction develops with hot working (extrusion). With subsequent cold working, the texture formed after extrusion alone becomes strengthened. This observation is attributed to the presence of a soft secondary phase (beta) at the alpha phase grain boundary. In contrast to the above, in the case of single phase Zircaloy 4, new components of texture are generated with cold deformation after hot extrusion, as a result of interaction between grains

Texture Development and Plastic Deformation in a Pilgered Zircaloy-4 Tube

The development of microstructure and crystallographic texture with effective strain at three through-thickness locations (near rolls, center, and near mandrel) in a partly pilgered Zircaloy-4 tube is described. Pilgering is found to eliminate through-thickness variation in grain size in the starting hot-extruded material and to generate location-dependent asymmetries in crystallographic texture. Deformation texture development during pilgering is modeled with polycrystal plasticity by idealizing the metal flow pattern as axisymmetric flow through a convergent channel. Good qualitative comparison of the predicted and experimental post-pilgering textures is obtained, provided location-dependent transverse shear component is superposed on the gross flow field, and localized deformation at grain boundaries is allowed. Frictional forces between tube and die are deduced from these observations. (C) The Minerals, Metals & Materials Society and ASM International 201

Deformation Twinning in Zirconium: Direct Experimental Observations and Polycrystal Plasticity Predictions

Deformation twinning was directly observed in three commercial zirconium alloy samples during split channel die plane-strain compression. One pair of samples had similar starting texture but different grain size distributions, while another pair had similar grain size distribution but different starting textures. Extension twinning was found to be more sensitive to the starting texture than to the grain size distribution. Also, regions of intense deformation near grain boundaries were observed. A hierarchical binary tree-based polycrystal plasticity model, implementing the Chin-Hosford-Mendorf twinning criterion, captured the experimentally observed twinning grains' lattice orientation distribution, and the twin volume fraction evolution, provided the critical resolved shear stress for extension twinning, was assumed much larger than any of the values reported in the literature, based on the viscoplastic self-consistent model. A comparison of the models suggests that obtained using the present model and the viscoplastic self-consistent models physically correspond to the critical stress required for twin nucleation, and twin growth, respectively. (C) The Minerals, Metals & Materials Society and ASM International 201

A miniature physical simulator for pilgering

Pilgering is a complex incremental manufacturing process for seamless tubes. In this work, a miniature physical simulator for pilgering was designed and fabricated. This miniature simulator employs a grooved roll-die and a mandrel and can impose controlled reductions in both tube diameter and wall thickness. Pilgering deformation over a range of ratios of reductions in wall thickness and in tube diameter, known as the Q-factor, was imposed on hemi-cylindrical zirconium alloy specimens. The influence of the Q-factor on the microstructure and deformation texture of the deformed specimens was quantified. A polycrystal plasticity calculation based on the binary tree model was used to simulate texture evolution during the simulated pilgering process. The computer model quantitatively captured the variation with Q of the Kearns factors, as measured in the physically simulated specimen. The small differences noticed between the predicted and experimental final textures point to unaccounted transverse components of the flow field. These observations suggest that physical and/or computer simulations can form the basis of a rapid methodology for tool selection to realize prescribed post-pilgering textures. (C) 2016 Elsevier B.V. All rights reserved