bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculation of beta induced Bremsstrahlung exposure from therapeutic radionuclide 198Au in tissues, DNA and RNA
Authors: Jabal-Ameli H. , Sadjadi S. , Ahmadi S. J. , Sadeghi M. , Bakht M. K.
Published: December 2013

Gold-198 (βmax=0.96MeV (98.6%), γmax=0.412MeV (95.5%) and T1/2=2.7 days) is a well-known therapeutic beta emitter in the field of nuclear medicine, and is being used for the treatment of many different cancers. In the present study, the Bremsstrahlung exposure induced by 198Au in different human tissues, DNA and RNA has been calculated. The specific Bremsstrahlung constant (ΓBr), Probability of energy loss by beta during Bremsstrahlung emission (PBr) and Bremsstrahlung activity (Arelease)Br were estimated. We strongly recommend these parameters should be considered in absorbed dose calculations of radionuclide therapy via 198Au.
Condensation-induced water hammer in a horizontal pipe
Authors: Martin C. Samuel
Published: December 2013

Experiments were conducted for the purpose of investigating the phenomenon of condensation-induced waterhammer in an ammonia refrigeration system. Waterhammer was initiated by introducing hot ammonia gas over static subcooled ammonia liquid placed in a horizontal 146.3mm diameter carbon steel pipe approximately 6.0m long. By means of fast response piezoelectric pressure transducers and a high speed data acquisition system rapid dynamic pressures were recorded whenever a condensation-induced event occurred. Moreover, by means of top-mounted diaphragm pressure transducers sensing gas pressure the speed of liquid slugs propagating along the pipe was determined. Based upon careful interpretation of the results criteria for the transition from initial stratified flow to slug flow were established, similar to the so-called Taitel-Dukler correlation in two-phase flow literature.
New practice for the evaluation of rod efficiency measurement by rod drop at the NPP Paks
Authors: Pós I. , Parkó T.
Published: December 2013

Measurement of rod efficiency is an important part of nuclear reactor safety. In case of operating power reactors it is usual to measure all rod efficiency at beginning of cycle hot zero power condition. Measurement of all rod efficiency is technically complicated because the measured “dynamic” reactivity cannot be compared directly to calculated “static” value of control rod efficiency. At Paks Nuclear Power Plant a new method was established to solve this problem. A static computer code used for reload safety analysis was extended to calculate core kinetics as well. Using the developed code the rod drop measurement itself is simulated and the time dependence of flux is determined. In addition, using Monte Carlo calculations weight functions are determined to describe the detector signal response to neutron flux changes in the reactor core. Using this combined system the detector signal itself can be simulated to the actual cycle and condition. Thus the measurement directly can be compared to simulation and the result can be evaluated. The method is under introduction to NPP Paks measurement practice and the first results – which are shown in the paper, are very promising.
Comparison of square and hexagonal fuel lattices for high conversion PWRs
Authors: Kotlyar D. , Shwageraus E.
Published: December 2013

This paper reports on an investigation into fuel design choices of a pressurized water reactor operating in a self-sustainable Th-233U fuel cycle. In order to evaluate feasibility of this concept, two types of fuel assembly lattices were considered: square and hexagonal. The hexagonal lattice may offer some advantages over the square one. For example, the fertile blanket fuel can be packed more tightly reducing the blanket volume fraction in the core and potentially allowing to achieve higher core average power density. The calculations were carried out with Monte-Carlo based BGCore code system and the results were compared to those obtained with Serpent Monte-Carlo code and deterministic transport code BOXER. One of the major design challenges associated with the SB concept is high power peaking due to the high concentration of fissile material in the seed region. The second objective of this work is to estimate the maximum achievable core power density by evaluation of limiting thermal hydraulic parameters. The analysis showed that both fuel assembly designs have a potential of achieving net breeding. Although hexagonal lattice was found to be somewhat more favorable because it allows achieving higher power density, while having breeding performance comparable to the square lattice case.
Determination of the nuclide vector for decommissioning projects at PSI (Paul Scherrer Institute, Switzerland)
Authors: Jäggi M. , Ehrlicher U. , Eikenberg J.
Published: December 2013

In the context of two reactor decommissioning projects, radioactive slurry from concrete cutting was collected in the retention pond (RHB) at the Paul Scherrer Institute, along with radioactive drain outlets. Additionally, there are active residues from former operations. The task was to determine the nuclide vector of the radioactive slurry before final disposal. Due to the slurry from neutron-activated concrete, activation products, like 55Fe, 60Co, 63Ni, 133Ba, 152Eu, 154Eu and 155Eu can be expected. Accumulated drain outlets from laboratories, where work with radioactive substances is being done, were expected to contain 22Na, 60Co, 134Cs, 137Cs, 133Ba, 152Eu, 154Eu, 155Eu, 241Am, 239/240Pu, 241Pu, 244Cm, 234U, 235U, 238U, 230Th, 232Th and 90Sr. For further clarification, 3H and 14C in the water and in the organic phase had to be measured as well. This work gives an overview about the slurry dissolution techniques, the radiochemical separation methods and activity concentrations of the nuclide vector. Further processing of the slurry is also discussed.
Effect of using FLiBe and FLiNaBe molten salts bearing plutonium fluorides on the neutronic performance of PACER
Authors: Acir A.
Published: December 2013

In this paper, the effects of using FLiBe and FLiNaBe Molten Salts Bearing Plutonium Fluorides on the neutronic performance of the PACER are investigated. The optimum radial thickness for tritium self-sufficiency of the blankets addition of plutonium fluorides to FLiNaBe (LiF-/NaF BeF2) and FLiBe (LiF-/BeF2) of a dual purpose modified PACER concept are determined. The calculations are carried out with the one dimensional transport code XSDRNPM/SCALE5. The tritium breeding capacities of FLiNaBe and FLiBe with addition of plutonium fluorides in molten salt zone are investigated and compared. The optimum molten salt zone thickness is computed as 155 cm for tritium self-sufficiency of the blankets using FLiBe +1% PuF4 whereas, the optimum thickness with FLiNaBe +1% PuF4 is calculated as 170 cm. In addition, neutron transport calculations have been performed to evaluate the energy multiplication factor, total fission rate, displacement per atom and helium gas generation for optimal radial thickness in the blanket. Also, the tritium production and the radiation damage limits should be evaluated together in a fusion blanket for determining the optimum thickness of molten salt layer.
Irradiation tests on PHWR type fuel elements in TRIGA research reactor of INR Pitesti
Authors: Horhoianu G. , Sorescu I. , Parvan M.
Published: December 2013

Nine PHWR type fuel elements with reduced length were irradiated in loop A of the TRIGA Research Reactor of INR Pitesti. The primary objective of the test was to determine the performance of nuclear fuel fabricated at INR Pitesti at high linear powers in pressurized water conditions. Six fuel elements were irradiated with a ramp power history, achieving a maximum power of 45 kW/m during pre-ramp and of 64 kW/m in the ramp. The maximum discharge burnup was of 216 MWh/kgU. Another three fuel elements with reduced length were irradiated with declining power history. At the beginning of irradiation the fuel elements achieved a maximum linear power of 66 kW/m. The maximum fuel power was about 1.3 times the maximum expected in PHWR. The maximum discharge burnup was 205 MWh/kgU. The elements were destructively examined in the hot cells of INR Pitesti. Temperature-sensitive parameters such as UO2 grain growth, fission-gas release and sheath deformations were examined. The tests proved the feasibility of irradiating PHWR type fuel elements at linear powers up to 66 kW/m under pressurized water conditions and demonstrated the possibility of more flexible operation of this fuel in power reactors. This paper presents the results of the investigation.
U
1 and P
1 approximations to neutron transport equation for diffusion length calculation
Authors: Bülbül A. , Öztürk H.
Published: December 2013

U
1 and P
1 approximations are used for the calculation of asymptotic relaxation length in one-dimensional neutron transport equation. The approximation methods are applied to anisotropic neutron transport equation with backward and forward scattering. The methods are based on the series expansion of the neutron angular flux in terms of the Chebyshev polynomials of second kind and Legendre polynomials. By applying the first order approximation to the transport equation, asymptotic relaxation lengths are calculated. Numerical results obtained from both methods are compared with each other.
A numerical method for resonance integral calculations
Authors: Tanbay T. , Ozgener B.
Published: December 2013

A numerical method has been proposed for resonance integral calculations and a cubic fit based on least squares approximation to compute the optimum Bell factor is given. The numerical method is based on the discretization of the neutron slowing down equation. The scattering integral is approximated by taking into account the location of the upper limit in energy domain. The accuracy of the method has been tested by performing computations of resonance integrals for uranium dioxide isolated rods and comparing the results with empirical values.
Condensation induced water hammer (CIWH) – relevance in the nuclear industry and state of science and technology
Authors: Swidersky H.
Published: December 2013

Condensation-induced water hammers (CIWH) are consequences of rapid condensation of steam in partially filled pipes. They present a particular hazard potential, as they seem to occur spontaneously and out of stagnation. The entire process still eludes a secured analytical or numerical predictability and determination of the fluid dynamic loads. The simulation of these processes is one of the most difficult tasks of thermal hydraulic transient analyses. Condensation induced water hammers in plants – mostly power plants – can lead to significant costs if they result in long downtimes, detailed analyses and upgrades. In this contribution, the phenomenon CIWH is explained and the relevance for nuclear engineering will be discussed. An outlook on the actual requirements of regulatory guidelines and the state of science and technology will be given.
1D Models for Condensation Induced Water Hammer in Pipelines
Authors: Blömeling F. , Neuhaus T. , Schaffrath A.
Published: December 2013

Condensation induced water hammer (CIWH) are caused by contact of steam and subcooled water. Thus, modeling the direct contact condensation is a crucial step towards the simulation of condensation induced water hammer with 1D pressure surge codes. Therefore, also the TÜV NORD SysTec GmbH & Co. KG inhouse pressure surge code DYVRO has been equipped with a new contact condensation model. The validation of DYVRO against an experiment dealing with CIWH is presented in this contribution.
Large Eddy Simulation of the shear flow instability in a rod-bundle assembly
Authors: Séverac E. , Fröhlich J.
Published: December 2013

The paper presents a Large Eddy Simulation at high Reynolds number of a section of a sub-channel in a fuel rod-bundle assembly of square pattern inside a pressurized water reactor. The focus is on the instability generated by the geometry of the sub-channel.
Numerical simulation of turbulent flow mixing inside a square chimney structure of a research reactor
Authors: Sengupta S. , Vijayan P. K. , Singh R. K. , Bhatnagar A. , Raina V. K.
Published: December 2013

Numerical simulation was performed to study the turbulent mixing behavior of two opposing flows inside a square chimney structure of a research reactor. The chimney design facilitates drawing pool water in the downward direction and thereby suppresses the upward flow of radioactive water jet to limit the radiation field at the reactor pool top. Analyses were carried out considering a mass flow rate of 750 kg/s for the upward flowing hot water from the core, which corresponds to Reynolds number of 3 × 106. Mass flow ratios of the downward flow and the upward flow were 0.0, 0.05, 0.1 and 0.15. The effects of mass flow ratio, chimney height on the velocity and temperature distribution inside three-dimensional chimney structure was evaluated using CFD code PHOENICS. The effect of temperature difference between the opposing flows on velocity was also analysed. It is observed that increase in downward flow causes the jet height to decrease due to the opposing momentum of downward flow against the upward jet. The effects of chimney height and temperature difference on the jet height are found to be marginal because of dominating inertial force over buoyancy force for the study.
Probabilistic safety analysis of external floods – method and application
Authors: Klügel J.-U.
Published: December 2013

The events of Fukushima amplified the scientific interest in the improvement of methods for probabilistic safety assessment (PSA) of extreme external events. The assessment of consequences of external floods belongs to this group of events. The paper presents the key steps of methodology for probabilistic safety assessment of external floods and a recent application for a nuclear power plant in Switzerland. The presented methodology is an extension of earlier activities and provides more focus on the PSA methodology part that may be applicable also for other studies.
Use of erbium as burnable poison for VVER reactors
Authors: Pavlovichev A. , Kosourov E. , Shcherenko A. , Saprykin V. , Lazarenko A. , Aleshin S. , Shcherenko A.
Published: December 2013

Problems related to use of Erbium as burnable poison for VVER are discussed. Comparison is made between neutronics characteristics of Uranium-Gadolinium and Uranium-Erbium fuel cycles. The study shows that use of Erbium as burnable poison allows decreasing the peaking factor in the core. Meanwhile residual Erbium at the end of the fuel cycle makes it necessary to increase fuel enrichment. There is made the conclusion of prospects of using Erbium as burnable poison for VVER.
The reactor dynamics code DYN3D and its trigonal-geometry nodal diffusion model
Authors: Duerigen S. , Rohde U. , Bilodid Y. , Mittag S.
Published: December 2013

The reactor dynamics code DYN3D is a three-dimensional best-estimate tool for simulating steady states and transients of light-water reactors and innovative reactor designs. An overview of the DYN3D features is provided. This paper further focuses on the recently developed trigonal-geometry diffusion model DYN3D-TRIDIF including a description of the underlying nodal approach and the characteristics of trigonal geometries. Via a mesh refinement study by means of a VVER-1000-type core benchmark using a fine-mesh diffusion reference solution, DYN3D-TRIDIF shows spatial convergence. Furthermore, the performance of DYN3D-TRIDIF is verified by means of a single-assembly problem on pin-cell level. Good agreement between DYN3D-TRIDIF and the detailed-geometry transport reference is achieved with an average deviation in power of less than 1%.
Robert W. Cahn: 1924–2007
Authors: Hardouin Duparc Olivier
Published: December 2013

R.W. Cahn died on the 9th of April. Wonderfully gifted from birth, his personality has been shaped by 20th Century history which forced him to flee from Germany to England through Spain. Chance and opportunities led him to study metallurgy at Cambridge and to later become one of the founders of Materials Science, and one of its best advocates. Some elements of his life and achievements are recalled here, as an homage to both the scientist and the man.
Solidification curves for commercial Mg alloys obtained from heat-transfer modeled DTA experiments
Authors: Mirković Djordje , Schmid-Fetzer Rainer
Published: December 2013

An improved method is presented for determination of solidification curves, i.e., solid fraction versus temperature, for commercial Mg alloys using heat-transfer modeled differential thermal analysis (DTA) curves. A better simulation of the measured DTA signal is attained through an independent measurement of the time constant as function of temperature for the applied equipment. This enables a better desmearing of the DTA signal. Challenging Mg alloys could be appropriately handled by redesigning the tantalum encapsulation. Due to high oxygen affinity and vapor pressure of the investigated magnesium alloys, this special adaptation of the DTA setup using sealed Ta capsules was indispensable for generation of reproducible and reliable data.
Analysis of phase formation in Ni-rich alloys of the Ni–Ta–W system by calorimetry, DTA, SEM, and TEM
Authors: Witusiewicz Victor T. , Hecht Ulrike , Warnken Nils , Fries Suzana G. , Hu Weiping
Published: December 2013

The partial enthalpies of dissolution of pure Ni, W and Ta in liquid ternary Ni–Ta–W alloys have been determined at (17735)K using a high temperature isoperibolic calorimeter. Measurements were performed in Ni-rich alloys (from 80 to 100 at.% Ni) along sections with constant Ta:W atomic ratios 1:0, 2:1, 1:2, and 0:1. The partial enthalpies and thereby the integral enthalpy of mixing of these ternary alloys are calculated from the partial enthalpies of dissolution using SGTE Gibbs energies for pure elements as reference.

The obtained thermochemical data confirm that in the investigated Ni-rich alloys the binary interactions between Ta and W as well as the ternary Ni–Ta–W interactions are negligibly small. Due to this the variation of the integral enthalpy of mixing of the ternary alloys is well described as linear combination of the constituent Ni–Ta and Ni–W binaries. Such behaviour of the ternary liquid alloys is related to a very low probability of new ternary stable phases to occur in solid state. This prediction is confirmed by differential thermal analysis, scanning electron microscopy, and transmission electron microscopy of the as-solidified and annealed samples obtained as last alloy compositions in the series of calorimetric dissolution.
Low temperature deposition with inductively coupled plasma
Authors: Lee Seung-Hoon , Jung Dong-Ha , Jung Seung-Jae , Hong Seung-Chan , Lee Jung-Joong
Published: December 2013

The processing temperature of chemical and physical vapor deposition could be successfully lowered by applying inductively coupled plasma without deteriorating the film quality. Despite the low process temperature, the deposition rate was higher than that observed in conventional deposition processes, and the impurity content could be kept low. Some examples of inductively coupled plasma applications e.g. TiB2, TiN, TiO2, and SnO2 films are shown.
Thermodynamic evaluation of the Al–Cr–C system
Authors: Hallstedt Bengt , Music Denis , Sun Zhimei
Published: December 2013

The system Al–Cr–C contains one ternary phase, Cr2AlC. By combining a Calphad assessment with ab initio calculations and differential thermal analysis, the Gibbs energy of Cr2AlC could be determined and the complete phase diagram calculated. Cr2AlC melts incongruently at about 1773K to form Cr7C3 (or Cr3C2) and Al4C3 in addition to liquid. According to the ab initio calculations the equilibrium composition of Cr2AlC is very nearly stoichiometric, but can dissolve some Al metastably by replacing Cr. The agreement between the thermodynamic calculation and the various sources of information is excellent.
Thermodynamic assessment of the Mn–Cr–O system for solid oxide fuel cell (SOFC) materials
Authors: Povoden Erwin , Grundy A. Nicholas , Gauckler Ludwig J.
Published: December 2013

By application of the CALPHAD method, a consistent set of thermodynamic model parameters is optimized for the Cr–Mn–O system based on experimental data. Chromium manganese spinel MnyCr3−yO4 and its tetragonally distorted polymorph are described using the compound energy model, and the liquid is described using the two-sublattice model for ionic liquids. Also solid solutions of the phases (Cr1–yMny)2+xO3, Mn2–yCryO3, and (Mn1–yCry)1–xO are considered. Relevance for solid oxide fuel cells is discussed.
The influence of porosity on the electrical properties of liquid-phase sintered silicon carbide
Authors: Ihle J. , Martin H.-P. , Herrmann M. , Obenaus P. , Adler J. , Hermel W. , Michaelis A.
Published: December 2013

The structure and the electrical properties of porous and dense liquid-phase sintered silicon carbide ceramics (LPS-SiC), containing yttria and alumina additives, have been studied.

The electrical resistance of LPS-SiC-materials varies in a wide range. This paper is focused on the influence of porosity on the electrical resistance of the sintered SiC. The porosity was controlled by the SiC grain size. Porous LPS-SiC materials were found to have substantially lower electrical resistance in comparison to dense materials of the same type.

The structure of the materials was investigated by XRD and FESEM. The porous materials consist of large grains due to the coarser starting powders in comparison to the dense materials. This results in a reduction of the dissolved and re-precipitated fraction of the SiC during sintering. Using the in-lens SEM mode, the high conductivity of the formed rims of the SiC grains could be shown. These observations reveal that the rim volume of dense LPS-SiC is much more extended than the rims of porous materials showing the higher conductivity.
Design of metal ceramic composites
Authors: Lenke Ilka T. , Rogowski Dirk
Published: December 2013

The reinforcement of light metal alloys with ceramic preforms offers a wide range of possibilities to improve mechanical and thermal properties and makes them usable for technical application. Starting with the Lokasil® composite material, different metal ceramic materials were created under serial-like conditions with the aim of improving the tensile strength, the bending strength, the thermal expansion, the damage tolerance, and the tribological properties.
High-temperature plasticity of SiC sintered with Lu2O3-AlN additives
Authors: Rixecker Georg , Biswas Koushik
Published: December 2013

SiC ceramics containing Lu2O3–AlN sintering additives were gas-pressure sintered, and creep testing in four-point bending geometry was performed at temperatures between 1200°C and 1500°C in air. Compared with the more conventional additive system Y2O3–AlN, the creep resistance of the Lu2O3-containing ceramics is higher. In particular, strain rates down to 610−10s−1were measured after 60h at both 1300°C/300MPa and 1400°C/100MPa; in no case was steady-state creep reached. Annealing the ceramics at 1950°C for extended periods of time led to significant changes in the amount and distribution of intergranular phases. However, in contrast to earlier work using Y2O3–AlN additives, the influence of annealing on the creep resistance was negligible. Compliance testing as a function of temperature was conducted in order to monitor the softening behavior of materials with different additive compositions. In favorable cases, the drop in stiffness was only 12% up to a test temperature of 1450°C.
Kinetics of precipitate formation in (TixWyCrz)B2 solid solutions: influence of Cr concentration and Co impurities
Authors: Schmidt Harald , Fotsing Roland E. , Borchardt Günter , Schmalzried Clemens , Telle Rainer
Published: December 2013

Supersaturated (Ti0.5−xW0.5Crx)B2 (x = 0, 0.1, 0,2) solid solutions were produced by reaction sintering of transition metal diboride powders at a pressure of 60MPa at 1800°C. The formation kinetics of W2B5 precipitates were investigated at lower temperatures by X-ray diffractometry (XRD) and secondary electron microscopy (SEM). The precipitation rate constants as a function of reciprocal temperature show non-monotonic behaviour in the range between 1450 and 1700°C with a maximum at about 1650°C. At low temperatures, Arrhenius behaviour is approximately valid, where the precipitation kinetics are dominated by the diffusion of the transition metals. In contrast, at temperatures higher than 1650°C, the precipitation rates decrease rapidly, since supersaturation, and consequently nucleation, is strongly reduced. The rate constants of precipitation are identical within error limits for Cr concentrations of x=0.1 and x = 0.2, however, they are significantly lower for x=0. This means that the addition of small amounts of Cr accelerates the precipitate formation, while further addition has no further influence. Samples resulting from powders which were high-energy milled with WC/Co hard balls before reaction sintering show an increased density of precipitated crystallites but no increased rate constants of precipitation. This result can be explained under the assumption that for these samples a significant amount of additional pre-existing nuclei was present before precipitation starts, which were formed by heterogeneous nucleation at Co impurities, introduced by the milling process.
Out-of-pile chemical compatibility of Pb–Bi eutectic alloy with Graphite
Authors: Sengupta A. K. , Bhagat R. K. , Laik A. , Kale G. B. , Jarvis T. , Majumdar S. , Kamath H. S.
Published: December 2013

Lead Bismuth eutectic alloy (Pb: 55.5wt.%, Bi: 44.5wt.%) is a potential candidate coolant material for high-temperature reactors because of its low melting point (124°C), high thermal conductivity, heat capacity, and better neutronic properties. Out-of-pile chemical compatibility studies of this coolant with graphite (coolant channel) have been carried out by isothermal annealing of the liquid alloy in a graphite crucible at 800, 900, 1000, and 1100°C for times ranging from 100h to 1000h. Formation of a reaction layer is observed. The growth rate of the reaction layer follows a parabolic law. Reaction layer thicknesses of 61.3 μm and 121 μm are estimated from the growth rate vs. time relation after 1year and 5years respectively. The growth of the reaction layer is diffusion-controlled and the activation energy of the reaction is estimated to be 100 KJ/mol.
Anelastic relaxation and structure of ternary Fe–Al–Me alloys with Me=Co, Cr, Ge, Mn, Nb, Si, Ta, Ti, Zr
Authors: Golovin I. S. , Strahl A. , Neuhäuser H.
Published: December 2013

The anelasticity of binary Fe–Al and ternary Fe–Al–Me (Me=Co, Cr, Ge, Mn, Nb, Si, Ta, Ti, Zr) alloys has been studied by mechanical spectroscopy in the Hz and kHz ranges. Relaxation peaks due to point defects – Snoek effect (S) with carbon interstitial jumps, carbon-vacancy complexes (X peak), Zener effect (Z), dislocations (D), and grain boundaries (GB) – are observed and their changes with addition of the third element are used to corroborate the respective proposed relaxation mechanisms, taking account of the changes of structure and order in the alloys which contain up to 5Co, 25Cr, 25Ge, 5Mn, 0.3Nb, 25Si, 6Ta, 4Ti, and 15Zr (all in at.%), respectively. In addition, some data of ordering temperatures, Curie temperatures, and hardness are provided for several alloys.
Temperature dependence of lattice mismatchand volume fraction of a fourth-generation monocrystalline nickel-based superalloy
Authors: Diologent Frédéric , Caron Pierre , d'Almeida Thierry , Chambreland Sylvain , Jacques Alain , Bastie Pierre
Published: December 2013

The strain distribution in a new generation nickel-based single crystal superalloy has been determined in the temperature range 293K–1598K. Measurements have been performed using diffraction of high energy synchrotron radiation (150keV, λ = 0.008 nm) to determine the variations with temperature of the γ/γ′ lattice mismatch and of the γ′ volume fraction. The chemical segregation at the dendrite scale and the internal stress induce a large range of values for the lattice mismatch. The measurements of the γ′ volume fraction determined by X-ray diffraction are in agreement with those obtained by atom probe tomography, image analysis or computation.
Filtration resistance during pressure filtration tests of liquid aluminium alloys
Authors: Cao Xinjin
Published: December 2013

Prefil Footprinter, a portable pressure filtration instrument, is usually employed to detect liquid metal quality. However, no investigations have ever been done to determine overall filtration resistance and resistance of the “clean” filter media. Based on the identification of flow behaviour using the derivative methods, classic filtration equations have been effectively used to estimate total filtration resistance for the first time. The variations of overall resistance during filtration provide a new approach to understand filtration behaviour. The resistance values of the “clean” filter media have been obtained for the first time. An innovative method has been developed to obtain the resistance of the “clean” filter media through the backward extrapolation of the overall filtration resistance versus filtrate weight or filtration time curves over the steady stages operating in incompressible cake mode.
Microstructure of a Damascene sabre after annealing
Authors: Reibold Marianne , Levin Alexander A. , Meyer Dirk C. , Paufler Peter , Kochmann Werner
Published: December 2013

X-ray phase analysis combined with high-resolution electron microscopy of samples taken from a genuine Damascus sabre after annealing for 24h at 400°C and 800°C followed by slow cooling down to room temperature has led to a better insight into the nature of cementite nanowires, which have been discovered recently. According to the present study, nanowires remained after 400°C annealing, but disappeared after heat treatment at 800°C and subsequent cooling down. On the other hand, perlitic cementite has been retained qualitatively after the same treatment. Knowing that the exceptional mechanical properties of Damascene blades disappear after annealing, the present results suggest a significant influence of the nanowires upon these features.
Multiwall carbon nanotubes-based composites – mechanical characterization using the nanoindentation technique
Authors: Olek M. , Kempa K. , Giersig M.
Published: December 2013

We report on mechanical properties of multiwall carbon nanotubes (MWNTs)-polymer composites using the nanoindentation technique. The nanoindentation experiments conducted on thin films containing MWNTs revealed that the presence of nanotubes does not affect the nanomechanical properties of the composites. Even a layer-by-layer assembly of MWNTs with a high concentration and a homogeneous distribution of carbon nanotubes does not ensure reinforcement of the composites. For that reason, we synthesized and utilized carbon nanotubes with a silica shell. Nanohardness and Young's modulus have been found to increase strongly with increasing content of these nanotubes in the polymer matrix. The silica shell on the surface of a nanotube enhances its stiffness and rigidity. Our composites, at 4wt.% of the silica-coated MWNTs, display a maximum hardness of 12020MPa and a Young's modulus of 91GPa. These are, respectively, 2 and 3 times higher than those for the polymeric matrix.
Mechanism of quasi-viscous flow of zinc single crystals
Authors: Pieła Krzysztof
Published: December 2013

This paper reports the results of mechanical investigations (tensile and relaxation tests), geometrical measurements as well as macro- and microscopic (slip traces) observations of zinc single crystals in the ‘hard’ orientation (from the line – of the standard triangle) tested in the temperature range 523–673K. Consideration of the experimental data lead to the conclusion that the quasi-viscous flow of crystals results from localized coarse slip in the basal system occurring in the structure of uniformly distributed slip in the 1st order prismatic (and/or the 1st order pyramidal) systems. The proposed mechanism explains the high strain-rate sensitivity and the ‘jerky’ character of the flow of the crystals.
Cooperating twin robots form a new X-ray diffractometer for stress analysis
Authors: Hessert Roland , Satzger Wilhelm , Haase Alfried , Schafmeister Achim
Published: December 2013

X-ray diffraction measurements on large components with complex geometry are needed in industrial applications requiring the non-destructive characterization of the near-surface material condition in terms of residual stresses, work hardening, phase transformation and formation of reaction compounds. Because many regions of interest on these components are not accessible with conventional laboratory or even mobile X-ray diffractometers, a novel center-free diffractometer with two cooperating robots named “Charon XRD” has been developed at MTU Aero Engines.

Two six-axis robots are synchronized using a special optical measuring system to achieve the highest positioning accuracies. This paper describes the actual design and operating mode of Charon XRD, its current and potential functionality, and presents calibration and reference measurements, along with results on aero-engine high-technology components like bladed integrated disks.
Cube textured tapes for use in YBa2Cu3O7–δ-coated conductor applications
Authors: Obst Bernhard , Nast Rainer , Kotzyba Gunter , Wetscher Florian
Published: December 2013

YBa2Cu3O7 is a high-temperature superconductor. Due to its complex lattice structure, belonging to the layered perovskite family, a strong biaxial texture of the grains is necessary to achieve technically relevant currents. In this paper, coarse-grained Ni, Ni-4at.% W, and electrolytic copper (E-Cu) obtained from swaged rods, and ultra-fine grained E-Cu produced by equal channel angular pressing, were thermo-mechanically processed. The development of the primary recrystallisation of the cube texture was studied and compared to determine the suitability of these materials as lattice-matched templates for coated conductor applications. Electron backscatter diffraction was performed to measure the texture and microstructure at various deformation levels and annealing temperatures. The texture sharpness formed in E-Cu with a coarse-grained starting microstructure proved superior, and it correlates with an anomaly observed in the temperature sensitivity of the flow stress in tensile tests, arising from crystal rotations.
Cavitation erosion of advanced ceramics in water
Authors: Litzow Ulrike , Gahr Karl-Heinz Zum , Schneider Johannes
Published: December 2013

The performance of advanced ceramics under cavitation loading in distilled water was studied by using a laboratory test with vibration-induced cavitation following the pattern of the ASTM standard G32–92. The hardened and tempered martensitic steel 100Cr6 was used as a reference. The aim was to identify mechanisms and the effects of important microstructural parameters on damage of polished Al2O3, Al2O3–ZrO2, ZrO2 and SiC ceramics. Results showed that surface damage of brittle ceramics was mainly dominated by intergranular fracture, followed by detachment of single grains or fragments of them. Both incubation time and erosion rate were affected by the amount of initial surface cavities, grain sizes and secondary phases at grain boundaries.
Microstructure and fatigue strength of the roller-bearing steel 100Cr6 (SAE 52100) after two-step bainitisation and combined bainitic–martensitic heat treatment
Authors: Vetters Hermann , Dong Juan , Bomas Hubert , Hoffmann Franz , Zoch Hans-Werner
Published: December 2013

Possible processes for shortening the heat treatment of roller-bearing steels in the lower bainitic range were investigated by computer assisted dilatometric experiments and by practical heat treatment process simulations. Several processes were evaluated and used on the steel 100Cr6 (SAE 52100). The microstructures achieved have been investigated by metallography, X-ray analysis and electron microscopy. Influences on hardness, as well as on the fatigue strength were examined. No loss in hardness was achieved and the fatigue strength, determined by rotating bar fatigue tests, was enhanced significantly by the shortened treatments, particularly by the use of the two-step bainitic treatment. The results indicated that small amounts of retained austenite, homogeneously dispersed on a sub-microscopic scale, as obtained during various treatment cycles, have influenced the fatigue strength. By means of the processes evaluated the heat treatment time can be shortened to about 10–25% of the duration of complete bainitisation in the lower range.
Description of flow curves over wide ranges of strain rate and temperature
Authors: El-Magd Essam , Treppman Christoph , Korthäuer Marcus
Published: December 2013

The relation between flow stress, strain rate and temperature is described by the same model over wide ranges of strain rates and temperatures. The model is developed on the basis of experimental data for flow curves of TiAl6V4, AA7075 (AlZnMgCu1.5) and steel Ck45N at temperatures varied between room temperature and 500°C, 900°C or 1000°C, respectively. The strain rate values cover the range between 10−3 and 8×10+3s−1. The model considers three simultaneously acting deformation mechanisms: creep deformation at high temperatures and low strain rates, thermally activated glide at low temperatures, and moderate to high strain rates and damping controlled deformation at very high strain rates. The model provides the data required for the simulation of high speed metal cutting and forming processes.
On the Hall–Petch relation between flow stress and grain size
Authors: Blum W. , Li Y. J. , Chen J. , Zeng X. H. , Lu K.
Published: December 2013

Data of flow stresses σ for pure Cu with ultrafine grains with grain size d ≍ 0:35 μm produced by severe plastic deformation and grains of conventional size obtained in the range of homologous temperatures T
hom from 0.22 (room temperature) to 0.33 are compared to data for hardnesses H for Cu of various grain structures from single crystalline to d = 0:01 μm measured by nanoindentation at room temperature. The two sets of data appear to be consistent when σ ≍ H=3. At room temperature the Hall – Petch relation holds, i. e., the flow stress increases monotonically with decreasing grain size by Δ σ ∝ d
−0.5. At elevated T
hom the saturated flow stress decreases when the grains become ultrafine. The transition from hardening to softening by grain boundaries in the saturation stage is discussed on the basis of a simple statistical dislocation model considering the influence of grain boundaries on the balance between generation and annihilation of dislocations.
Effect of a low frequency electromagnetic field on the direct-chill (DC) casting of AZ80 magnesium alloy ingots
Authors: Guo Shijie , Le Qichi , Zhao Zhihao , Han Yi , Cui Jianzhong
Published: December 2013

The effects of a low frequency electromagnetic field applied during semi-continuous direct-chill casting on AZ80 ingots were investigated. The experiments were performed both in the absence and in the presence of the electromagnetic field. In contrast to the ingot cast in the conventional process, the microstructure of the ingot was significantly refined by the electromagnetic field and a high degree of grain refinement was realized when the operating frequency was at 22Hz. The ingot exhibited a relatively increased and uniform distribution of Vickers hardness and decreased segregation of Al when the operating frequency of the electromagnetic field was in the range of 15–30Hz.
Synthesis and characterization of MgAlON–BN composites
Authors: Zhang Zuotai , Li Wenchao , Wang Xidong , Seetharaman Seshadri
Published: December 2013

In the present paper the Gibbs energy of formation of MgAlON was evaluated, and on this basis the phase stability diagram of Mg – Al – O – N – B was established. Dense magnesium aluminium oxynitride – boron nitride (MgAlON – BN) composites with 0 – 30 vol.% BN were synthesized by hot pressing in the temperature range 1750 – 1850 °C in the phase stability region. The phase compositions of the composites analyzed by X-ray diffraction indicated that the main phases were MgAlON and h-BN and no impurities were found. The microstructures of the composites analyzed by transmission electron microscopy, scanning electron microscopy, and high-resolution electron microscopy showed that the MgAlON did not react with BN, and the latter was distributed on the grain boundary of MgAlON homogeneously. Excessive BN (> 20 vol.%) resulted in a discontinuous microstructure for MgAlON. A matrix-flushing method was employed in the quantitative X-ray diffraction analysis for the multi-component MgAlON – BN composites. The results showed that the relative MgAlON content decreased in the process of sintering MgAlON – BN composites. Thermodynamic analysis showed that some Al2O3, AlN, and MgO escaped under the reaction conditions. The lattice parameters of MgAlON in the composites have also been evaluated.
Mechanical properties of rope-reinforced aluminium extrusions under quasistatic loading conditions
Authors: Weidenmann Kay André , Fleck Claudia , Schulze Volker , Löhe Detlef
Published: December 2013

Compound-extruded unidirectionally reinforced lightweight profiles are a novel class of materials for the construction of load-bearing structures. In this paper, investigations of the reinforcing effect of ropes in compound-extruded aluminium profiles tested under quasistatic loading conditions are presented. In particular, the investigations lead to a characterisation of the interface between matrix and reinforcing element, as the compound's internal load transfer is a crucial factor in the overall mechanical properties. It could be shown that – in addition to a form fit – a diffusional bond evolves. Both Young's modulus and tensile strength could be increased by using a rope reinforcement. Furthermore, the results attained are compared to a theoretical model which was adapted to the deformation behaviour of compounds containing a single reinforcement.
Density and atomic volume in liquid Al–Fe and Al–Ni binary alloys
Authors: Plevachuk Yuriy , Egry Ivan , Brillo Jürgen , Holland-Moritz Dirk , Kaban Ivan
Published: December 2013

The density of liquid Al – Fe and Al – Ni binary alloys have been determined over a wide temperature range by a non-contact technique combining electromagnetic levitation and optical dilatometry. The temperature and composition dependences of the density are analysed. A negative excess volume correlates with the negative enthalpy of mixing, compound forming ability and chemical short-range ordering in liquid Al – Fe and Al – Ni alloys.
Superplastic deformation behavior of a spray-deposited eutectic NiAl/Cr(Mo) alloy doped with Dy
Authors: Du Xinghao , Wu Baolin , Huang J. C.
Published: December 2013

The tensile deformation behavior at elevated temperatures and the associated mechanisms are investigated for hot isostatically pressed NiAl-28Cr-5.9Mo-0.1Dy fabricated through spray forming. Superplasticity is observed at above 1323 K under an initial strain rate lower than 10−3 s−1 with an m value of 0.5. The activation energies for superplastic flow are found to be half of that for self-diffusion in NiAl. Grain boundary sliding between NiAl and adjacent NiAl or Cr(Mo) grains with local range accommodation, i. e., dynamic recovery, is suggested to be responsible for the superplastic deformation of the alloy.
The influence of Nd on the corrosion behavior of electroless-deposited Fe–P
Authors: Meng Yan , Wang Ling-Ling , Huang Gui-Fang , Huang Wei-Qing , Zou Bing-Suo
Published: December 2013

Fe – Nd – P layers were prepared by electroless deposition. Discussed in this paper is the influence of the rare earth element Nd on the deposition rate, mixed potential, anti-corrosion performance, structure, and surface morphology of the deposit. The results show that the deposition rate increases with the addition of Nd and the increment can be as high as 30 %. The addition of Nd also improves the homogeneity of the deposit, eliminates pores, and reduces the particle size. Electroless Fe – P deposits incorporated with Nd also exhibit significantly improved anti-corrosion performance, especially in alkaline media.
Microstructure and mechanical properties of AZ91D alloy prepared by a semi-solid diecasting process
Authors: Du X. H. , Zhang E. L. , Wu B. L.
Published: December 2013

Semi-solid processing has been combined with die-casting for the magnesium alloy AZ91D. The microstructure of the semi-solid diecast AZ91D has been examined by optical microscopy and scanning electron microscopy. No pores were visible under optical microscopy, indicating a very low porosity. Mechanical properties of the semi-solid diecast AZ91D alloy have also been tested. High ultimate tensile strength and elongation have been achieved due to the low porosity and the fine microstructure. The fracture surfaces have been investigated by scanning electron microscopy in order to reveal the fracture mechanism. A typical inter-granular fracture surface was observed, indicating that the alloy fails in a brittle manner. The vertical-section microstructure of the fractured sample has indicated that the crack mainly propagates along the grain boundaries through the brittle fracture of the eutectic phase or the interface decohesion of the primary Mg phase and the eutectic phases.
Grain refinement and texture formation in torsion deformed NiAl
Authors: Klöden Burghardt , Rybacki Erik , Oertel Carl-Georg , Skrotzki Werner
Published: December 2013

Torsion at elevated temperatures and pressures was used to severely deform the intermetallic compound NiAl. The microstructure and texture as a function of shear strain were investigated by orientation imaging microscopy and diffraction of synchrotron radiation, respectively. The results show that at high shear strains a steady state grain structure and texture develops by continuous dynamic recrystallisation. The lowest grain size achieved is in the micron range, the main texture component is {110}<100>. It is concluded that high-strain torsion may open new possibilities in terms of grain refinement, texture formation and ductilisation of NiAl.
Deformation processing of massive nanostructured materials
Authors: Wilde Gerhard , Dinda Guru Prasad , Rösner Harald
Published: December 2013

Deformation processing of initially polycrystalline material can lead to ultrafine-grained or even to nanocrystalline material, depending on the applied deformation route. In addition to different grain sizes, materials processed by different deformation methods also display different thermal stabilities. In order to analyze the impact of defects – particularly dislocations – near the grain boundaries, pure Pd and pure Ni have been processed sequentially by different methods. Transmission electron microscopy investigations at high resolution were conducted to characterize the microstructures of the materials. In addition, geometrical phase analysis was used to locate defects and visualize their strain fields. The results indicate that the presence of a high dislocation density at the grain boundaries increases the stability of the nanocrystalline structure against coarsening.
Multiscale modelling of nanoindentation
Authors: McGee Edward , Smith Roger , Kenny S. D.
Published: December 2013

The process of nanoindentation causes physical phenomena not only at the nano-scale, but at multiple length scales up to the macroscopic. We present a model that links atomistic scale molecular dynamics to a finite element model in order to extend the length scales that can be modelled. We illustrate how this has been used in some studies of nanoindentation, to test the coupled model, and secondly to compare the results to atomistic only models. These studies show that by extending the length scales, the results from the model are in closer agreement with the experiment.