bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study on the Formation of Serrated Grain Boundaries and its Applications in Nimonic 263
Authors: Hong Hyun Uk , Jeong Hi Won , Kim In Soo , Choi Baig Gyu , Yoo Young Soo , Jo Chang Yong
Published: January 2010

The formation of serrated grain boundaries and its subsequent effect on creep resistance have been investigated in a wrought nickel based superalloy Nimonic 263. The grain boundaries were considerably serrated without the presence of γ' phases or M23C6 when a specimen was slow-cooled from the solution treatment temperature. The high resolution observation on the lattice image of the serrated grain boundary suggested that the grain boundaries tended to serrate to have specific segments approaching to one {111} low-index plane at a boundary in order to have lower interfacial free energy of grain boundary. The grain boundary serration led to a change in M23C6 carbide characteristics: the carbide morphology from granular to planar, a lowered density and their coherency pattern to two neighboring grains from consistent to zigzag. The improvement of creep resistance was noticeably observed by the introduction of GB serration without deterioration of basic mechanical properties. This improvement in creep resistance by the serration was associated with a lower rate of cavitation and crack propagation through the modification of carbide characteristics as well as grain boundary configuration.
Metadynamic Recrystallization of the Nickel-Based Superalloy Allvac 718PlusTM
Authors: Sommitsch Christof , Huber Daniel , Stockinger Martin
Published: January 2010

During hot working of the recently developed nickel based alloy Allvac 718PlusTM softening kinetics like dynamic, metadynamic as well as static recrystallization govern the microstructure evolution during and after hot forming and hence the final mechanical properties. In this work the metadynamic recrystallization was investigated using double hit compression tests. The classical methodology of offset stress comparison was not usable because of discontinuous yielding of this material. Thus a new method to describe the softening during metadynamic recrystallization was developed, which compares the deformation energy at equal strains, i.e. the area beneath the true strain vs. true stress curve, of the first and second hit as well as at steady state.
Phase Transformation Behavior of Boron Containing 9% Cr Heat Resistant Steels
Authors: Tokunaga T. , Kaku H. , Miyazaki H. , Masuyama F.
Published: January 2010

The phase transformation behavior of 9Cr–3W–3Co–VNb steels with boron contents of 47 and 130 ppm has been investigated using differential thermal analysis (DTA). In our DTA experiments, disk-shaped samples were normalized and then tempered at temperatures between 10 and −50 °C from the ferrite-to-austenite transformation temperature (Ac1) at a rate of 30 °C/min. The measured Ac1 temperatures for 47 ppm B steel and 130 ppm B steel were 878 and 884 °C, respectively. The general features of the phase transformation behavior and the changes in hardness with tempering temperature for these boron containing steels were almost identical, irrespective of the boron content. In the DTA cooling curves during tempering at temperatures between −30 and 10 °C from the Ac1 temperatures, an exothermic peak due to the formation of fresh martensite was observed and the peak area increased with increasing tempering temperature. The Vickers hardness values measured after the DTA experiments decreased gradually with increasing tempering temperature, reaching a minimum value of about 180 HV around Ac1−40 °C, and then increased markedly, reaching a value of about 350 HV at Ac1+10 °C.
Heat Treatment and Oxidation Characteristics of Nb-20Mo-15Si-5B-20(Cr,Ti) Alloys from 700 to 1400°C
Authors: Natividad Sylvia , Acosta Arianna , Amato Krista , Ventura Julieta , Protillo Benedict , Varma S.K.
Published: January 2010

Nb-20Mo-15Si-5B-20(Cr,Ti) alloys have been subjected to annealing treatment for 2 hours in a range of temperatures from 700 to 1400oC and quenched in water to perform the microstructural characterization for these two new alloys. As cast structure consists of a solid solution phase, , and silicides (Nb5Si3) in both alloys but Cr alloy also contains NbCr2 and Nb3Si phases. Heating to higher temperature introduces Ti silicides in the microstructure for Ti alloy. The oxidation in air has been conducted on these alloys in the same temperature range for 24 hours. Weight gain per unit area as a function of temperature provides the oxidation curves while characterization techniques using SEM, EDS on SEM, x-ray mapping, and XRD has yielded the analyses of the oxide scale. The scale consists of various oxides of Nb, Mo, Cr, Si, and Ti. Cr alloy appears to offer higher oxidation resistance in the selected range of oxidation temperatures.
The Halogen Effect for Ni-Base Superalloys – A Thermodynamic Study
Authors: Zschau Hans Eberhard , Masset Patrick J. , Schütze Michael
Published: January 2010

A new method for the oxidation protection of Ni-base superalloys with relatively low Al-content is proposed. By using the halogen effect the Al activity on the surface can be increased. Thus, the formation of a pure protective alumina scale becomes possible. The alloys IN738 and IN939 are considered in the present paper. Thermodynamic calculations for fluorine and chlorine predict the existence of the halogen effect for both alloys at temperatures between 900°C and 1200°C. The results also predict a change of the oxidation mechanism from internal alumina formation to external oxidation.
Influence of Steel Grain Size on Residual Stress in Grinding Processing
Authors: Gotoh Masahide , Seki Katsuhiro , Shozu M. , Hirose Hajime , Sasaki Toshihiko
Published: January 2010

The fine-grained rolling steels NFG600 and the conventional usual rolling steels SM490
were processed by sand paper polishing and mechanical grinding to compare the residual stress
generated after processing. The average grain size of NFG600 and SM490 is 3 μm and 15μm
respectively. Therefore improvement of mechanical properties for such fine-grained steels is
expected, it is important to understand the residual stress state of new fine-grained materials with
processing. In this study, multi axial stresses of two kinds of specimens after polishing and grinding
were measured by three kinds of analysis methods including cos-ψ method. As a result, as for σ33, the
stress of NFG was compression, though that of SM490 was tension.
X-Ray Investigation on Strength of Thin Films
Authors: Takao Hanabusa , Shinohara Mitsuhiko
Published: January 2010

The behavior of thermal stresses and residual stresses in aluminum and copper thin films were investigated by the diffraction of X-rays and synchrotron radiations. Aluminum films were exposed in an elevated temperature in order to measure the thermal stress behavior in the films. Thermal stresses in the films in thin aluminum and copper films of 10 nm to 1000 nm thickness with and without passivation payer were measured in a sequence of thermal cycles. Stresses in thick films without passivation traced along with a hysteresis loop during thermal cycles, whereas the thin films of nano-meter size with AlN passivation layer behaved in a linear way with the temperature change. Thin copper films with and without AlN passivation layer were used to investigate strengthening mechanism of thin films. Specimens with different thickness of the films were subjected to a cyclic plane bending fatigue test. Residual stresses developed in the films were measured in a sequence of bending cycles to understand the effect of film thickness and passivation layer on mechanical properties of thin films. The film of 500 nm thickness developed less residual stresses in the film than thicker films. A passivation layer was effective to prevent residual stress development in the film.
The X-Ray Diffraction Characteristics of Different Materials
Authors: Zhang Yi Liang , Liu Zhao Miao , Liu Jin Yan
Published: January 2010

The x-ray diffraction characteristics of different materials are discussed in this paper. It is found that the accurate determination of real stress is not easy to obtain when two diffraction peaks with low diffraction intensity are shown and the residual stress of stainless steel, aluminum, titanium alloy materials etc are determined by X-ray method. Five kinds of uniform intensity girders made from common carbon steel (Q235), austenite stainless steel (1Cr18Ni9Ti), martensitic stainless steel(A335P92), aluminium alloy(LY12) and titanium alloy(TA15) are determined repeatedly using uniform intensity girder demarcation method. It is proved by experiment results that X-ray diffraction peaks at some angles can’t well reflect the real change of stress.
Analysis of Residual Stress for Butt Welding of Thick Plate
Authors: Nakatani Mitsuyoshi , Abe Masamitsu , Murakawa Hidekazu , Sasaki Toshihiko
Published: January 2010

There are few reports that evaluated quantitatively the effect of the PWHT (Post Weld Heat Treatment) on the weld residual stress relaxation. We studied the residual stress for butt welding of thick plate. We conducted the experiment and the thermo-elastic-plastic finite element analysis. We became to be able to estimate the residual stress distribution of the butt weld. Also we clarified the effect of the PWHT on the weld residual stress.
Induction of Engineered Residual Stresses Fields and Associate Surface Properties Modification by Short Pulse Laser Shock Processing
Authors: Ocaña José Luis , Morales Furió Miguel , Porro J.A. , Blasco M. , Molpeceres C. , Iordachescu D. , Gómez-Rosas G. , Rubio-González C.
Published: January 2010

Laser shock processing (LSP) is consolidating as an effective technology for the improvement of metallic materials surface properties involving their fatigue life. The main acknowledged advantage of the LSP technique consists on its capability of inducing a relatively deep compression residual stresses field into metallic alloy pieces allowing an improved mechanical behaviour, explicitly the life improvement of the treated specimens against wear, crack growth and stress corrosion cracking. Progress accomplished by the authors in the line of practical development of the LSP technique at an experimental level, aiming its integral assessment from an interrelated theoretical and experimental point of view, is presented in this paper. Concretely, experimental results on the residual stress profiles and associated surface properties modification successfully reached in typical materials (especially Al and Ti alloys) under different LSP irradiation conditions are presented, a correlated analysis of the residual stress profiles obtained under different irradiation strategies and the evaluation of the corresponding induced surface properties as roughness and wear resistance being also presented. Through a coupled theoretical- experimental analysis the real possibilities of the LSP technique as a possible substitutive of related traditional surface modification techniques as, for example, shot peening.
Transmission Imaging and Strain Mapping in the Vicinity of Internal Crack Tip Using Synchrotron White X-Ray
Authors: Shibano Junichi , Kajiwara Kentaro , Kiriyama Koji , Shobu Takahisa , Suzuki Kenji , Nishimura Suguru , Miura Setsuo , Kobayashi Michiaki
Published: January 2010

A transmission imaging and a strain mapping in the vicinity of a crack tip in steel were investigated using a high energy white X-ray obtained from BL28B2 beam line at SPring-8 in Japan. Low-alloy and high-tensile steel was used as a specimen prepared in the G-type geometry with a rectangular sectional part of 5mm thickness for a four-point bending. A fatigue crack was introduced into the notch root on the tension side of the specimen by a pulsating bending load. The imaging of the crack in the specimen under the bending load was carried out by using the CCD camera that can detect indirectly the X-ray transmitted through the specimen. To measure the internal strain in the vicinity of the crack tip, the synchrotron white X-ray beam, which had a height of 80m and a width of 300m, was incident on the specimen with the Bragg angle  of 5 degrees using the energy dispersive X-ray diffraction technique. As the results, the transmitted image of the crack showed that the crack in the specimen was propagated deeper than that on the surface. The map of the internal strain near the crack tip could be obtained using the white X-ray with energy ranging from 50keV to 150keV. It became clear by the numerical simulation that the FWHM of diffracted X-ray profile measured near the crack tip was increased due to the steep change in the strain distribution. It was confirmed that the synchrotron white X-ray was useful for the imaging of the internal crack and the strain mapping near it.
High Temperature Internal Friction Behavior of Unidirectionally Solidified Al2O3/YAG Eutectic
Authors: Ueno Shunkichi , Takata Satoshi , Tanabe Yasuhiro , Akatsu Takashi , Yasuda Eiichi , Waku Yoshiharu
Published: January 2010

In this paper, the internal friction behaviors of unidirectionally solidified Al2O3/YAG eutectic that are examined by the authors in passed several years are reviewed. The internal friction of this eutectic increased with increasing temperatures above 1200oC. The apparent activation energy of the eutectic sample in the range from 1100 to 1400oC was same to that of Al2O3 single crystal. Above 1200oC, the internal friction of this material drastically increased with increasing temperatures. The magnitude of the internal friction strongly depended on the elevated temperatures and the cycle numbers of the torsional loading. For the 1400oC test, the internal friction gradually increased with the loading cycles and then saturated by 103 times of the loading cycles.
Industrial Research and Development with Synchrotron Radiation
Authors: Kroschewski Katja , Webb Adam , Wroblewski Thomas , Wurr Karsten
Published: January 2010

The outstanding properties of synchrotron radiation (SR) allow manifold investigations of materials and processes which are not possible with conventional X-ray sources. Its high brightness allows extremely precise or time/spatial resolved measurements. In combination with its high collimation extremely high angular resolution is achievable. The white spectrum of SR allows tuning of the wavelength for spectroscopic applications or optimization according to the requirements of the experiment.
Comparison of the Mechanical Properties of Hastelloy X Material after Welding by GTAW and Nd-YAG Laser
Authors: Wu Shih Jeh , Du Chao Wei , Kuo Chen Ming
Published: January 2010

Cracks induced by metal fatigue and structural aging effect can’t be fixed by traditional Gas Tungsten Arc Welding (GTAW), consequently cause the increasing of defect ratio. Although some cracks might be acceptable and qualified to field service standard subject to the military regulation, however, in certain areas, e.g. brazing and coating areas, the results are not ideal especially the HAZ and residual stress. In this study, Nd-YAG Laser welding and traditional GTAW processes were performed on Hastelloy X superalloy for comparison. Post-welding residual stress distribution was measured by X-ray diffraction method. Macro- and microstructure were observed by metallurgical OM and SEM in comparison to the hardness testing. Tensile test results show that traditional welding technology has better ultimate tensile strength and ductility. For the Nd:YAG laser welding, residual stress is limited to 3mm of the both sides of weld and drops drastically, while higher amplitude and widely spread in the GTAW welding. It is proposed that combining both methods, the repairing process can be optimized to reduce the defect ratio and save repairing time.
Hierarchical 3D/4D Characterization on Deformation Behavior of Austenitic and Pearlitic Steels
Authors: Adachi Yoshitaka , Ojima Mayumi , Morooka Satoshi , Tomota Yo
Published: January 2010

This study highlites deformation behavior of austenitic and pearlitic steels by in-situ neutron diffraction and 3D/4D EBSD measurement with a particular attention to their hierarchy.In particular stress partitioning in these microstructures is examined from macroscopic as well as microscopic scale length levels, and they are correlated to each other.
Electron Tomography of Nanostructured Materials – Towards a Quantitative 3D Analysis with Nanometer Resolution
Authors: Kübel Christian , Niemeyer Dirk , Cieslinski Robert , Rozeveld Steve
Published: January 2010

Electron tomography has developed into a powerful technique to image the 3D structure of complex materials with nanometer resolution. Both, TEM and HAADF-STEM tomography exhibit tremendous possibilities to visualize nanostructured materials for a wide range of applications. Electron tomography is not only a qualitative tool to visualize nano¬structures, but recently electron tomographic results are also exploited to obtain quantitative measurements in 3D. We evaluated the reconstruction and segmentation process for a heterogeneous catalyst and, in particular, tried to assess the reliability and accuracy of the quantification process. Furthermore, a quantitative analysis of electron tomographic results was compared to macroscopic measurements.
Three-Dimensional Visualization and Analysis of Grain Deformation by Means of Synchrotron Radiation
Authors: Kobayashi Masakazu , Toda Hiroyuki , Uesugi Kentaro
Published: January 2010

The new method to investigate and visualize a strain distribution at individual grains in three-dimensional has been developed based on synchrotron radiation X-ray tomography. The tensile specimen made of a heat-treated 2024 aluminum alloy to coarse precipitate particles has repeatedly scanned by the high-resolution X-ray tomography with applying a loading just before fracture would occur. Grain boundaries in the specimen were visualized by the tomographic scan after gallium application in order to detect grain regions in three-dimensional. Total 17 grains were found by 2D and 3D image processing and were provided with strain analysis by means of the microstructural features tracking. The actual strain development on a grain was visually demonstrated during tensile deformation. The strain map on a cross section of the grain shows inhomogeneous distribution. In the vicinity of grain boundary, the partly large strain is observed. The strain distribution within a grain seems to be affected by neighbor grains. The different evolution of strain distribution was also confirmed in the two grains while the grains were deformed almost equivalently on an average. The difference of deformation microstructure depending on grain orientation is suggested.
Investigation of the Surface Characteristics for the Micro-Cutting Process with Finite Element Simulation
Authors: Autenrieth Hermann , Weber Matthias , Deuchert M. , Schulze Volker
Published: January 2010

As the service life of components is significantly influenced by the surface layer properties, namely surface roughness, surface work hardening and residual stresses, these are the focus of many investigations. As these properties can be measured experimentally in many cases only after finish of the process, simulation models can be used to explain the final process results by the interpretation of the development of the result quantities during the loading and unloading state. The developed and validated simulation model and the extended process knowledge can be used afterwards to predict process parameter combinations with optimal process results for other cutting tool-workpiece combinations without performing large and costly experimental investigations.
In the present study, the dependences of surface work hardening and residual stresses on process parameters of micro-cutting, namely cutting depth, cutting velocity and cutting edge radius are investigated by 2D finite element simulations using ABAQUS/Standard. The material behaviour of normalized AISI 1045 is described in dependence of strain, strain rate, and temperature. Chip formation is modelled by continued remeshing of the work piece. The simulation results are validated by the comparison with experimentally determined integral width and residual stress depth profiles, using x-ray diffraction method. The influence of the ploughing process, characterized by the ratio of cutting edge radius to cutting depth, on surface characteristics is well described by the simulation model.
Fractal Model for Snow
Authors: Carbone Anna , Chiaia Bernardino , Frigo Barbara , Türk Christian
Published: January 2010

We analyze the distribution of grains in solid cubes of ice in terms of deterministic and stochastic 3d fractal models. We argue that the fractal dimension D or the Hurst exponent H optimally describe the void distribution in the snow sample and can be used as a parameter to describe the mechanical properties of snow at different scales.
Multiscale CAFE Modelling of Dynamic Recrystallization
Authors: Kuc Dariusz , Gawąd Jerzy , Pietrzyk Maciej
Published: January 2010

The paper is focused on application of multi-scale 2D CAFE method. CAFE approach consists of Cellular Automata (CA) model of microstructure development and the thermal-mechanical finite element (FE) code. Dynamic recrystallization phenomenon is taken into account in 2D CA model which takes advantage of explicit representation of microstructure, including individual grains and grain boundaries. Flow stress is the main material parameter in mechanical part of FE and is calculated on the basis of average dislocation density obtained from CA model. The results attained from the CAFE model were validated with the experimental data for austenitic steel X3CrNi18-9. The samples were subjected to axisymmetrical hot compression test. Compression forces were recorded during the tests and flow stresses were determined using inverse method. Light microscopy and EBSD analyses were performed for the initial and final microstructures of the samples.
Simulation of Copper Precipitation in Fe-Cu Alloys
Authors: Holzer Ivan , Kozeschnik Ernst
Published: January 2010

During ageing of Fe-Cu alloys, for standard ageing conditions, peak hardness and strength is often observed after several hours. The significant strengthening is attributed to a dense distribution of very small bcc-Cu precipitates of 2-3 nm size. Using conventional numerical precipitation kinetics models for diffusion-controlled transformations, the kinetics of strengthening cannot be consistently described. One of the issues in this aspect is the fact that, after reaching peak hardness, a strong decrease in number density is observed experimentally, which cannot be explained by classical Ostwald ripening theory. In the present study, a new methodology for simulation of the copper precipitation kinetics in the early stage is suggested. The basic idea of this approach is to take into account the composition variation of the Cu-precipitates with respect to the Fe content during the precipitation reaction. The simulation results are compared to experimental data reported in literature. Consistent agreement between experiment and simulation can be achieved with the new methodology.
The Analyze of Phase Transformations in Ultra Fine Grained Constructional Steel
Authors: Dyja Henryk , Koczurkiewicz Bartosz , Knapiński Marcin
Published: January 2010

In the present work, low-carbon ultra grained constructional low-alloyed steel were subjected to thermo-mechanical treatment for modification of microstructure. It shows that microstructure after thermo-mechanical treatment is quite dependent on the alloy composition, conditions of hot deformation, grain size of austenite and cooling rate. The research was provide by using the computer program for thermo and thermo – mechanical treatment. The most optimal variant of heat treatment and thermo – mechanical deformation were obtained. The verifications were provided by the dilatometer with possibility of deformation DIL 805A/D.
High-Temperature Testing of the Properties of Blast Furnace Coke
Authors: Konstanciak Anna
Published: January 2010

The article describes the behaviour of coke in the blast furnace. Factors, which cause weakening and degradation of coke lumps at temperatures above 1300°C have been analyzed. On the basis of preliminary testing of samples taken from a blast furnace at different distances from the tuyère outlet and tests for thermo-abrasion ξ, the advisability of using the pre-tuyère chamber for the assessment of coke quality at high temperatures has been indicated. Thermodynamic calculations for the determination of the chemical composition of the products of reaction of coke ash mineral substances with elementary carbon and air, as well as the behaviour of coke at high temperatures under inert gas conditions are presented. The number of compounds forming from coke ash components during heating in a stream of gases of highly differential reductiveness reflects the complexity of the physicochemical phenomena.
The Influence of Rolling Temperature on the Energy and Force Parameters during Normalizing Rolling of Plain Round Bars
Authors: Laber Konrad Błażej , Dyja Henryk , Mróz Sebastian
Published: January 2010

The paper presents results of theoretical and experimental studies on the influence of strip temperature reduction at the final stage of the normalizing rolling process in a continuous bar rolling mill on the energy and force parameters. The studies were carried out for 38 mm-diameter round bars of constructional steel S355J2G3 (St52-3 acc. to DIN).
At the first stage, numerical modelling of the rolling process was performed for the conditions of the currently used rolling technology. The aim of this stage of the work was to determine the distribution of strip temperature during the rolling process and of strip temperature after the rolling process. The obtained computation results were compared with the measurement results recorded during the actual rolling process using a thermovision camera. A computer program designed for three-dimensional modelling of metal flow during rolling in passes was used for the determination of the distribution of strip temperature during rolling.
The second stage of the studies included modelling of the bar rolling technology modified by applying normalizing rolling after introducing accelerated strip cooling at the final stage of rolling. The aim of this stage of the work was to establish the influence of reduced strip temperature on the change in the values of the energy and force parameters of the process.
By comparing the computed values of rolling power with those of the permissible power it was found that these values were lower than the permissible power of the rolling machine’s main drives installed in the Rolling Mill under analysis. Thus, it was demonstrated that it was possible to implement the process of normalizing rolling in the conditions of the Shape Mill under study.
Design of Process Equipment Beam Joints to Utilise Stress Relaxation
Authors: Pöllänen Ilkka , Martikka Heikki
Published: January 2010

In design of process equipment and hot vessel beam joints the real effect of relaxation is considered. Standards make an allowance that some relaxation of stresses at joint could be advantageous in relieving the stress peaks due to reaction moments. Magnitude of the moments in itself is not the problem but the stress distribution caused by it. The goal in this study is to estimate the possibility of taking advantage of relaxation in design using as test case a rectangular beam. Analytical theory of creep is applied with constant bending moment load. Stress distribution is first linear elastic and then flattens to nonlinear form resembling the elastic plastic bending. FEM gave analogous results constant moment and time dependent strain. One advantage is that fatigue life is increased at these joints after moderate amount of creep relaxation.
Numerical Modeling of Casting Solidification Using Generalized Finite Difference Method
Authors: Mochnacki Bohdan , Majchrzak Ewa
Published: January 2010

The system casting-mould is considered. The thermal processes proceeding in a casting sub-domain are described using the one domain approach. The model of solidification process is supplemented by the energy equation concerning the mould sub-domain, the continuity conditions given on the contact surface between casting and mould, boundary conditions on the outer surface of the system and the initial ones.
To solve the problem the generalized variant of finite difference method (GFDM) is used. Temporary and local values of temperature can be found at the optional set of collocation points from the domain considered. This essential advantage of GFDM allows to locate and thicken nodes at the regions for which the temperature gradients and cooling (heating) rates are considerable. In the final part of the paper, the example of numerical simulation is shown.
Thermal Behaviour of Steel Plate during Accelerated Cooling
Authors: Pyykkönen J.M. , Martin David C. , Somani Mahesh Chandra , Mäntylä P.T.
Published: January 2010

Recent trends in the production of high strength steel plate call for increasingly sophisticated thermo-mechanical treatment schedules, including the use of high rate accelerated cooling after finish rolling in order to achieve the desired microstructure and mechanical properties. Achieving the necessary cooling process control accuracy in such cases requires a sound understanding and description of the interactions between external heat transfer processes and changes in internal energy due to phenomena such as solid-state phase transformations. The thermal physical properties of the evolving microstructures of complex phase and martensitic steels vary greatly, and are strongly dependent on temperature and constituent phases. As a result, critical parameters such as thermal diffusivity cannot be accurately estimated without appropriate linkage to both phase transformation kinetics and temperature. In the present study, a numerical simulation has been developed to investigate the unsteady heat transfer and phase transformation behaviour of a moving steel plate during accelerated cooling. The simulation includes semi-empirical microstructure evolution sub-models, fitted to measured CCT data using non-linear regression. These are coupled to thermal-physical properties sub-models and thermal conduction calculations. A comprehensive suite of thermal boundary condition models which account for direct water cooling, forced convection film boiling, air cooling, radiation and heat transfer between plate and transport rollers are also included. The required equations for the plate temperature and microstructure evolution are solved numerically using a cell centred finite volume method, and the model has been validated by comparing simulated cooling stop temperatures with measurements obtained on the plate cooling section of an industrial plate mill. The predicted cooling stop temperatures of steel plates for different thicknesses, velocities and water flow rates are in good agreement with plant operational data.
Interaction of the Precipitation Kinetics of δ And γ’ Phases in Nickel-Base Superalloy ATI Allvac® 718PlusTM
Authors: Radis Rene , Zickler Gerald A. , Stockinger Martin , Sommitsch Christof , Kozeschnik Ernst
Published: January 2010

In this paper, the precipitation behaviour of  (Ni3(Nb,Al)) and ’ (Ni3(Al,Ti,Nb)) phases in the nickel-base superalloy ATI Allvac® 718PlusTM, as well as their kinetic interactions are discussed. Important parameters such as volume fraction, mean radius and number density of precipitates are experimentally determined and numerically simulated as a function of the heat treatment parameters time and temperature. To match the experimentally observed kinetics, the predicted interfacial energy of the precipitates, as calculated for a sharp, planar phase boundary, is adjusted to take into account the interfacial curvature and entropic effects of a diffuse interface. Correction functions for the interfacial energies of  as well as ’ precipitates are presented. Using these modified interfacial energies, the calculated results show excellent agreement with the experimental measurements.
Microcracked Materials as Non-Simple Continua
Authors: Trovalusci Patrizia , Varano Valerio
Published: January 2010

A non-simple continuum model is adopted to grossly describe the behaviour of elastic microcracked bodies. The constitutive relations, obtained using a multiscale modelling based on the hypotheses of the classical molecular theory of elasticity, allow taking into account the microscopic features of the material. Referring to a one-dimensional microcracked bar, the possibility of the continuum to reveal the presence of internal heterogeneities is investigated.
Crystallographic Textures Variation in Asymmetrically Rolled Steel
Authors: Wroński Sebastian , Wierzbanowski Krzysztof , Bacroix Brigitte , Wróbel Mirosław , Wroński M.
Published: January 2010

The crystallographic texture formation in low carbon steel during asymmetric rolling was studied experimentally and analysed numerically. Modelling of plastic deformation was done in two scales: in the macro-scale using the finite element method ( FEM) and in crystallographic scale using the polycrystalline deformation model (LW model). The stress distribution in the rolling gap was calculated using FEM and next these stresses were applied in LW model of polycrystalline plastic deformation. In general, the predicted textures agree very well with experimental ones.
The Effects of Different Precipitation States on the Annealing Behaviour of AA6111
Authors: Chang Cynthia S.T. , Duggan B.J.
Published: January 2010

In this work the nucleation of the Cube recrystallised grains in AA6111 was investigated. The alloys were cold rolled to 85% and then annealed at different temperatures in an air circulation furnace. X-ray diffraction was used to obtain global textures and for specific area of interest, Electron-Back Scattered Pattern (EBSP) was used. In order to observe the microstructures after rolling and partially annealing, Scanning Electron Microscopy (SEM) was used. It was found that the recrystallisation textures are strongly related to the annealing temperature. The recrystallisation texture after low temperature annealing gives a strong retained rolling texture and at high temperature, a fairly random texture with weak Cube and rotated Cube components. The difference in the volume fraction of Cube with different alloys and annealing temperature are related to the deformation microstructures. Cube bands are observed to be deformation bands on the rolling plane. During annealing, precipitates are formed on the deformation band boundaries and Cube nuclei which are formed in the deformation Cube band are restricted to growth due to the precipitates.
Microstructure and Texture Optimization in Fe-Si Ferritic Steels
Authors: Gobernado Patricia , Petrov Roumen H. , Ruiz Daniel , Leunis Elke , Kestens Leo A.I.
Published: January 2010

The ferromagnetic properties of ferritic steels are known to strongly depend on the direction of magnetization. The <100> are the axes of spontaneous magnetic moments and hence the directions of easy magnetization. Materials displaying a <100>//ND texture are ideal not only for transformer but also for rotating machines due to their isotropic magnetic character. In the present study the potential of severe plastic rolling deformation is investigated. The cold rolling and annealing microstructures and textures are identified with increasing rolling strains to a maximum vM equivalent of 8.0. It is shown that excessive rolling reduction is capable of producing non-conventional texture components with promising potential for magnetic applications.
Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Films Prepared by a Coaxial Arc Plasma Gun
Authors: Nakagawa You , Yoshitake Tsuyoshi , Hanada Kenji , Nagano Akira , Ohtani Ryota , Sumitani Kazushi , Setoyama Hiroyuki , Kobayashi Eiichi , Hirakawa Masaaki , Yamaguchi Koichi , Tsukahara Naoki , Agawa Yoshiaki , Nagayama Kunihito
Published: January 2010

Growth of ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite films without initial nucleation was realized by an coaxial arc plasma gun at a substrate-temperature of 550 °C and hydrogen-atmosphere of 53.3 Pa. The pulsed arc discharge was triggered at a repetition rate of 1 Hz. The deposition rate was 80 nm/min. X-ray diffraction measurements with 12-keV X-rays from synchrotron radiation indicated extremely broad rings from diamond and none from graphite. The UNCD crystallite diameters were estimated to be approximately 1.3 nanometers by using Scherrer’s equation. The sp3/(sp2+sp3) was estimated to be approximately 57% from the X-ray photoemission spectroscopy. The coaxial arc plasma gun is a new powerful method that might enable us to realize the supersaturated condition with highly energetic ions for the growth of UNCD.
Structural Changes in Nickel Silicide Thin Films under the Presence of Al and Ga
Authors: Mogilatenko A.V. , Allenstein Frank , Schubert M.A. , Falke Meiken , Beddies G. , Neumann Wolfgang
Published: January 2010

Thin Ni/Al and Ni/Ga layers of different atomic ratios were codeposited onto Si(001) at room temperature followed by subsequent annealing. Influence of annealing temperature on morphology and composition of ternary disilicide NiSi2-xAlx and NiSi2-xGax layers was investigated by transmission electron microscopy. Addition of Al or Ga leads to a decrease of the disilicide formation temperature from 700°C down to at least 500°C. Depending on the composition closed, uniformly oriented NiSi2-xAlx and NiSi2-xGax layers were observed after annealing at 900°C, whereas reaction of a pure Ni film with Si leads to the island formation with a mixture of A- and B-type orientations.
A Study on Hydrogen in Titanium Thin Films
Authors: Tal-Gutelmacher Ervin , Gemma Ryota , Nikitin Eugen , Pundt Astrid , Kirchheim Reiner
Published: January 2010

Titanium and its conventional alloys reveal a high affinity for hydrogen, being capable to absorb up to 60 at.% hydrogen at 600°C, and even higher contents can be alloyed with titanium at lower temperatures. Hydrogen exhibits a low solubility in the low-temperature hexagonal closed-packed (hcp) α phase and a very high solubility (up to 50 at.%) in the high temperature body-centered cubic (bcc) β phase. The presence of hydrogen in the amount exceeding 200 ppm leads to formation of hydrides in α and α + β titanium alloys. While the aforementioned hydrogen behavior within bulk titanium has been well-established and reviewed, this is not the case with titanium thin films. The interpretation of results in these nanosized systems is complicated because the exact determination of the hydrogen concentration is difficult. However, using electrochemical hydrogen loading technique under the proper conditions, the hydrogen concentration can be accurately determined via Faraday’s law. In this study the thermodynamics of the titanium films during hydrogen absorption were investigated by electromotive force (EMF) measurements. Titanium films of different thicknesses were prepared on sapphire substrates in an UHV chamber with a base pressure of 10-8 mbar, using ion beam sputter deposition under Ar-atmosphere at the pressure of 1,5ּ10-4 mbar. The crystal structure was investigated by means of X-Ray diffraction using a Co-Kα radiation. For electrochemical hydrogen loading, the films were covered by a 30 nm thick layer of Pd in order to prevent oxidation and facilitate hydrogen absorption. The samples were step-by-step loaded with hydrogen by electrochemical charging, which was carried out in a mixed electrolyte of phosphoric acid and glycerin (1:2 in volume). An Ag/AgCl (sat.) and Pt wires were used as the reference and the counter electrode, respectively. XRD measurements were performed before and after hydrogenation in order to investigate the effect of hydrogen loading on the films microstructure. The role of varying thicknesses on the main characteristics of hydrogen's absorption behavior, as well as hydrogen-induced microstructural changes in titanium thin films, are discussed in detail.
In Situ S-Doping of Cubic Boron Nitride Thin Films by Plasma Enhanced Chemical Vapor Deposition
Authors: Yang Hang Sheng , Kurebayashi Norihiko , Yoshida Toyonobu
Published: January 2010

In situ sulphur doping of cubic boron nitride (cBN) films was investigated by adding H2S into a plasma-enhanced chemical vapor deposition system. It was found that the nucleation of cBN was suppressed severely with a very low H2S concentration, while cBN could be grown continuously even at a H2S concentration as high as that of the boron source after its nucleation. Accordingly, S was incorporated into cBN films meanwhile keeping the cubic phase concentration as high as 95%. And a rectification ratio of approximately 10 5 was observed at room temperature for heterojunction diodes prepared by depositing S-doped cBN films on p-type silicon substrates, which suggests the possibility of an n-type-like doping. Moreover, 1500K post annealing of cBN films in H2 atmosphere was found to be able to release the residual compressive stress evidently. Thus, film adhesion strength increased markedly, and cBN films reached a thickness over 200 nm without peeling off from silicon and quartz substrates in air after 9 months.
Work Hardening and Tensile Behaviour of an Austenitic Stainless Steel at High Temperature
Authors: Angella Giuliano
Published: January 2010

The work hardening and tensile behaviour of AISI 316L austenitic stainless steel deformed at temperatures between 600 and 1000°C has been investigated. The alloy has been heat-treated according two different roots: the first solutioning treatment was imposed at 1100°C and the second was designed at 875°C to reduce the dynamic ageing that occurs at temperatures up to 650°C in AISI 316L. In the solutionised material the work hardening data presented two linear regions: at high stresses the linearity has been described as the conventional Stage III of work hardening, whilst at low stresses the linearity has not been rationalised in any conventional stage of work hardening. In the second heat treatment alloy the work hardening data showed a single linear region at high stresses, whilst no linear stage occurred at low stresses. Therefore, the work hardening and tensile behaviour of AISI 316L has resulted to be significantly affected by the two different heat treatments and dynamic aging has been proved to influence work hardening behaviour well beyond the range of temperatures in which serrated yielding occurs.
Reasons for Formation of Twin-Precipitates in Two Phase Stainless Steel
Authors: Miyano Naoki , Takahashi Akihiro , Kataoka Seigo , Ameyama Kei
Published: January 2010

This study focuses on the entire shape of the  twin-precipitate in two phase stainless steel, Fe-25Cr-6Ni in terms of the interphase and elastic strain energies generated between the precipitate and matrix. An investigation of this precipitation is important not only in terms of microstructure control but also for improving the mechanical properties of materials. Firstly, the three-dimensional near-coincidence site lattice (3D-NCS) model, which is based on the atomic matching model, is applied for estimating the preferred habit planes by evaluating the result of geometrical atomic matching. Subsequently, the precipitate shape is determined from candidates of the preferred habit plane produced by the 3D-NCS model, and the elastic strain surrounding and within the precipitate is investigated by FEM analysis, which can calculate the anisotropic elastic strain depending on the shape of the precipitate. The results are compared with observed precipitate by TEM.
Melting and Solidification in the System Fe-Mn-C
Authors: Lob A. , Senk Dieter , Geimer S.
Published: January 2010

At the Department of Ferrous Metallurgy (IEHK) steels grades in the system Fe-Mn-C are under investigation, because extraordinary mechanical properties of these steels result from the metal-physical deformation-mechanism. The microstructure forming and the deformation-mechanism are regulated by the chemical composition. The aim of the project, in the frame of SFB 761, is focused on the formation of model materials with different alloying composition and cooling rates, as well as the determination of melting and solidification parameters and their influencing factors. One task is the metallurgical treatment of critical elements for high manganese steels; the gases hydrogen, nitrogen and oxygen. A problem to be solved is that the melting of high manganese steels tends to manganese losses in the liquid.
Analysis of Hot Tensile and Compression Curves to Assess the Hot Ductility of C-Mn Steels
Authors: Varela-Castro Gonzalo , Calvo Jessica , Cabrera Jose María
Published: January 2010

The unbending operation is a critical stage of steel continuous casting because it is carried out at thermomechanical conditions for which embrittlement mechanisms can appear leading to transverse cracking. The hot tensile test is commonly used to simulate such thermomechanical conditions, at the surface of the slab, and, the reduction in area of the samples tested to fracture is taken as a measure of the susceptibility to cracking of the steel. However, a further metallographic and fractographic evaluation of the samples is required in order to identify the embrittlement mechanisms. These mechanisms are usually related to transformations in the microstructure, such as precipitation or the appearance of deformation induced ferrite, which imply changes in the strength of the material and should therefore be detectable in the flow curves. However, the features of tensile curves are not usually analyzed when evaluating the hot ductility because necking makes the interpretation of the curves complicated. In this work the hot ductility of a C-Mn steel will be discussed by means of hot tensile and compression tests. The embrittlement mechanism identified for this steel is the appearance of a ferrite layer at austenite grain boundaries. The effect of this mechanism on the features of the tensile curves will be discussed. Moreover, these curves will be compared to compression curves obtained under the same testing conditions to see whether transformation induced ferrite can be detected by means of hot compression testing. The possibility of assessing the ductile behavior of different steel grades through hot compression, which requires less material and is easier to control, will be discussed.