bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Low Carbon Microalloyed Bainitic Steels for Structural Plate Applications
Authors: Ormston D. , Schwinn Volker , Hulka Klaus
Published: March 2009

Steels with bainitic microstructures show the capacity to fulfil the requirements of high strength and low temperature toughness necessary for plate steels in specialised industrial constructions. The introduction of steels with higher strength allows for weight reductions of steel constructions. This paper investigates the development of hot rolled structural plate steels through laboratory hot rolling simulations of thermo-mechanically controlled processes (TMCP). Specific
alloying and microalloying along with an optimised TMCP process has allowed high tensile properties to be achieved in combination with high levels of toughness. Tensile strengths of up to 900 MPa have been achieved with Charpy V-notch toughness greater than 200J at –40°C. Elements such as molybdenum, niobium and boron have been added to low carbon steels to promote the formation of fully bainitic microstructures with much lightened chemical compositions. The presented concepts allow the production of steel grades above S500 up to S690.
Characterisation of Bimodal Grain Structures and Their Dependence on Inhomogeneous Precipitate Distribution during Casting
Authors: Chakrabarti D.J. , Davis Claire L. , Strangwood Martin
Published: March 2009

Bimodal grain size distributions were found in continuously cast slab and thermomechanical controlled rolled (TMCR) samples of Nb-microalloyed steel. Scanning electron microscopy (SEM) revealed inhomogeneous distributions of Al- and Nb-containing precipitates, which were found to pin prior austenite grain boundaries during reheating. An effort has been made to establish parameters to quantify the extent of bimodality of reheated and rolled microstructures. Quantification of bimodality using peak grain size range, (PGSR) and peak height ratio, (PHR), is found to match closely with the visual observation of bimodality. Thermo-Calc software was used to predict the sequence of precipitation for different compositions and that could explain the formation of bimodality during reheating.
Effect of Processing Parameters on Precipitation Reactions Occurring in a Ti-Bearing IF Steel
Authors: Kuziak Roman , Hartman Hansjörg , Budach Marina , Kawalla Rudolf
Published: March 2009

The investigation was focused on the detailed description of precipitation/formation processes of TiN, TixSy, Ti4C2S2, TiC, and (Fe,Ti)P particles occurring in the production of thin sheets of titanium-bearing interstitial-free steels. The knowledge concerning this reactions was gained based on the thermodynamic calculation and physical simulations conducted on Gleeble 3800 thermal – mechanical simulator. The formation process of titanium carbosufide of Ti4C2S2 is the crucial reaction for the thin sheets properties. The investigation confirmed the in-situ mechanism of this phase formation, involving carbon diffusion in the TiS and TixSy sulfides’ crystal lattice. Thus, the precipitation of the substantial fraction of these sulfides is a prerequisite for further intense carbosulfide formation. Titanium sulfides are formed at the rough rolling stage of the transfer bar rolling process. The most intense precipitation of the sulfides occurs at around 1000°C. Besides the effect on the carbosulfide formation, it was found out that the sulfides substantially retard the recrystallization and grain growth in the IF steels. The most favourable Ti4C2S2 formation conditions prevail in the temperature range of approximately 950 - 920°C, which corresponds to the plate finish rolling stage. Both reactions, i.e. sulfides and carbosulfide formation, are deformationinduced processes.
Optimisation of V/N Ratios and Stelmor Cooling for Electric Arc Furnace Steels Used in Galvanised High Tensile Strength Wire Applications
Authors: Wallace Andrew , Brownrigg Allan , Hodgson Peter  D. , Frawley Leo , Heath Warwick
Published: March 2009

The high level of residual nitrogen in Electric Arc Furnace (EAF) steels is one of the major factors influencing the performance of the finished product. For high tensile strength galvanised wire applications, nitrogen in interstitial solid solution can severely limit drawability and formability. This problem can be controlled simply and effectively by adding nitride-forming elements to the molten steel so that the nitrogen is removed from solution. Vanadium additions are especially beneficial in high strength steels because the removal of nitrogen as vanadium-nitride can cause extensive precipitation strengthening. This investigation concerns commercial grade steels microalloyed with vanadium and rolled to 5.5mm rod, under controlled Stelmor cooling conditions. This rod is used to produce 2.5mm high tensile strength galvanised wire. The aim of the research was to determine the optimum vanadium/nitrogen (V/N) ratio and Stelmor cooling profile for the vanadium steel rod. This was achieved by extensive production and laboratory trials followed by
mechanical and microstructural analyses of the product.
Deformation Modes and Anomalous Strengthening of Ni3X -Type Intermetallic Compounds with the Geometrically Close-Packed Structure
Authors: Umakoshi Yukichi , Hagihara Koji , Nakano Takayoshi
Published: March 2009

Plastic deformation behavior including anomalous strengthening of Ni3X-type compounds with D019, D0a and D024 structure were examined and summarized, focusing on the correlation between deformation characteristics and features of their crystal structures.
Material Processing Using Supersonic Reactive Plasma Jets in Thermodynamical and Chemical Nonequilibrium State
Authors: Tahara Hirokazu , Fujiuchi Kenji , Ando Yasutaka
Published: March 2009

Nitriding of metals and reactive spraying for nitride ceramics are planned using a 10-kW-class direct-current nitrogen or H2/N2-mixture arc plasma jet generator with a supersonic expansion nozzle in a low pressure environment. The H-atom electronic excitation temperature and the N2 molecule-rotational excitation temperature intensively decreased downstream in the nozzle although the NH molecule-rotational excitation temperature did not show an axial decrease. As approaching the titanium plate for nitriding, the thermodynamical nonequilibrium plasma came to be a temperature-equilibrium one. Both the electron number density near the plate and the heat flux into the plate increased with H2 mole fraction for mixtures gases. In cases with H2/N2-mixtures, a radical of NH with a radially wide distribution is considered to contribute to the better nitriding as a chemically active and non heating process. Numerical simulation was carried out to examine interactions between injected ceramic particles and the nitrogen plasma flow. When plasma was accelerated to supersonic flow through the nozzle, ceramic particles were smoothly accelerated by the aerodynamic drag force and heated in the highly-reactive plasma flow. The calculated results showed that the supersonic plasma jet in thermodynamical and chemical nonequilibrium state might have some potentials for material processing, even for spraying, because of its high reactivity.
Internal Friction Influenced by Hydrogen in Super Duplex Stainless Steels
Authors: Kuroda Toshio , Nakade Katsuyuki , Ikeuchi Kenji
Published: March 2009

The influence of microstructure concerning sigma phase on hydrogen behavior was investigated by means of internal friction analysis. After hydrogen charging, a sharp significant internal friction peak by hydrogen in austenite of as-received specimen was observed at 245K for a frequency of 1.5Hz. However, the peak height in the specimen precipitated significant sigma phase was substantially lower than in as-received specimen since hydrogen in austenite have a concentration lower by sigma phase precipitation. In addition, the broadening and scattering of the internal friction peak was clearly identified by interaction between hydrogen and sigma phase. It means that the two peaks associated with hydrogen in the both sigma phase and austenite were considered to be overlapped. Consequently, it was clearly confirmed that hydrogen entered in the sigma phase lattice and hydrogen was also trapped at sigma/austenite interfaces.
Al2O3/Al2O3 Joints Brazed with Composite Active Filler Materials Obtained by Mechanical Alloying
Authors: Fang Hong Yuan , Yang Jian Guo , Hu Jun Feng
Published: March 2009

The joints of Al2O3/Al2O3 are brazed with (Ag72Cu28)97Ti3-10vol.%Al2O3 composite filler materials, in which Ti and Al2O3 particulates mixed-powders are obtained by mechanical alloying (MA). The analysis results of brazed joints by the SEM, EPMA and XRD indicate that the Ti and Al2O3 particulates in mixed-powders are enwrapped and intermixed into composite particulates. Diffusion and distortion of atoms lattice of both components in mixed-powders occur during MA processes. The shear strength tests of Al2O3/Al2O3 ceramic joints show that the joints just have the normal properties. Otherwise, compensation of Ti into the (Ag72Cu28)97 Ti3 -10 vol. % Al2O3 composite filler materials, which are made by mechanical alloying, has important influence on the properties of joints, the study indicate that the highest shear strength of this kind of joint is 139MPa.
Diode Laser Brazing of Heat-Resistant Alloys Using Tandem Beam
Authors: Saida Kazuyoshi , Song Woo Hyun , Nishimoto Kazutoshi , Shirai Makoto
Published: March 2009

The diode laser brazing of heat-resistant alloys with precious filler metals has been conducted using tandem beam which consisted of preheating beam and main brazing beam. The 1mm thick Inconel 600 and A286 alloys were laser-brazed with the 0.5mm diameter Au-18%Ni, Ag-10%Pd and Ag-21%Cu-25%Pd filler metals using a brazing flux. The processing parameters of laser power of tandem beam and brazing clearance were varied. Sound butt joints could be obtained by using tandem beam with laser powers of 200-400W/100-150W even at the narrow gap brazing below 0.3mm where the melted filler metal did not infiltrate completely the joint gap by only using the main brazing beam (single beam). The tensile strength of the brazed joint using Ag-Pd filler metal increased with decreasing brazing clearance and attained about 70% of the base metal strength at brazing clearance of 0.1mm, while those using Au-Ni and Ag-Cu-Pd filler metals were comparable to the base metal strength at any brazing clearance between 0.1-1.5mm. The preheating during the tandem beam brazing resulted in superior brazability at the narrow gap to wide gap brazing because of the improvement in wetting/spreading and erosion esistance of melted filler metal by depressing the extremely high peak temperature and steep temperature distribution in the base metal.
Effects of High Temperature ECAE Process on Microstructures and Martensitic Transformation of TiNi Shape Memory Alloy
Authors: Xie Chao Ying , Fan Z.G. , Li Z.H. , Xiang G.Q. , Cheng X.H.
Published: March 2009

Microstructures and transformation behavior of TiNi shape memory alloy after high temperature ECAE process have been investigated. It is found that the initial coarse grains were refined after high temperature ECAE processes and short annealing at 750°C. Transformation temperatures of TiNi alloy sharply decreased after two ECAE processes, rose obviously when annealed at 750°C for 5min, and quickly rose back after annealing at 500°C for 2 hours. Reasons for phase transformation behavior changes have been discussed.
Nanocrystalline Structure in Steels Produced by Various Severe Plastic Deformation Processes
Authors: Umemoto Minoru , Todaka Yoshikazu , Li Jin Guo , Tsuchiya Koichi
Published: March 2009

The formation of nanocrystalline structure in steels by ball milling, shot peening and
drilling were studied. In ball milling and shot peening, nanocrystalline layers form with sharp boundaries from deformed structure regions. Nanocrystalline layer showed extremely high hardness. By annealing, nanocrystalline layer showed substantially slow grain growth without recrystallization. The temperature of the specimen during deformation is low and deformation is done in ferrite state. In drilling, several μm thick nanocrystalline layers form at the top surface of a drill hole. Nanocrystalline layers showed high hardness and good thermal stability. The fresh martensite and retained austenite near a drill hole indicate that the temperature reached above Ac3 and nanocrystalline layers are produced in austenite condition. It is recognized that nanocrystalline layers produced in the processes studied in the present investigation has similar characteristics irrespective of the temperature it produced. It is proposed that deformation with a large strain gradient is an important condition to produce nanocrystalline structure.
Deformation Mechanism of Nanocrystalline Al-Fe Alloys by Analysis from Ab-Initio Calculations
Authors: Uesugi Tokuteru , Takigawa Yorinobu , Higashi Kenji
Published: March 2009

Recently nanocrystalline Al-Fe alloys produced by a vapor quench method have been reported. These alloys are supersaturated solid solution and exhibit high strength with good ductility. It is postulated that the high strength of the Al-Fe alloys could be achieved by both the nano-grained structures and the solid solution strengthening. The contribution to the yield strength due to both the grain size strengthening and the solid solution strengthening were analyzed from the experimental data. Then the contribution to the yield strength due to the solid solution strengthening was estimated from the misfit strain calculated from the first principles in order to compare with analytical results estimated from the experimental data.
The Positive Role of Back-Pressure in Equal Channel Angular Extrusion
Authors: Lapovok Rimma
Published: March 2009

Equal Channel Angular Extrusion (ECAE) has become a very popular tool for studying the evolution of microstructure and properties under severe plastic deformation. It is believed that the stress-strain characteristics are uniform in a cross-section of the billet and this uniformity of the stress-strain distribution ensures the uniformity of microstructure and mechanical properties in ECAE processed billet. However, some experimental data such as the fracture of the extruded billet, which is initiated at the inner surface of the sample, has caused doubts about uniformity of stress-strain distribution. This non-uniformity has been proved recently by Finite Element Simulation.

In this paper the studies of the positive role of the applied back-pressure during ECAE are reviewed and the influence of a back-pressure on the uniformity of the stress-strain distribution, strain localisation, die corner filing, and the prevention of fracture is shown. The effect of back-pressure on grain refinement and improvement in mechanical properties is emphasized. The paper summarises our results from over seven years of work using a unique machine for ECAE with computer-controlled back-pressure and velocity of the backward punch.
Evaluation of a Ni-20Cr Alloy Processed by Multi-Axis Forging
Authors: DiDomizio R. , Gigliotti M.F.X. , Marte J.S. , Subramanian P.R. , Valitov Vener
Published: March 2009

This paper discusses the development of a novel processing route to produce ultra finegrain bulk alloy forgings; the microstructural response of these forgings to thermal exposure; and the comparison of mechanical properties to those from conventionally processed material. A Ni- 20Cr [wt%] alloy was processed by near-isothermal multi-axis forging to a grain size of approximately 1 μm. A heat-treatment study over the range 900 to 1200°C was conducted to determine the resultant grain size as a function of time and temperature. Tensile properties were measured at room temperature, 500°C, and 930°C. High-cycle fatigue properties were measured at room temperature. The room-temperature tensile strength was approximately 2.5 times greater than that of conventionally processed Ni-20Cr. Fatigue data showed that the room-temperature highcycle fatigue run-out stress was greater than 100% of the yield stress.
TEM Investigations of Titanium Processed by ECAP Followed by Cold Rolling
Authors: Mingler Bernhard , Stolyarov V.V. , Zehetbauer Michael J. , Lacom Wolfgang , Karnthaler Hans Peter
Published: March 2009

Conventional coarse grained (CG) commercial pure (CP) Ti Grade 2 was studied after cold rolling (CR) at room temperature, and after equal channel angular pressing (ECAP) at 450° C followed by CR, by transmission electron microscopy (TEM) methods. CR of the CG material leads to a microstructure showing initially twins with (0112) type and later subgrains separated by lowangle grain boundaries. CR carried out after ECAP yields the fragmentation of fine grains (300 – 800 nm) mostly bounded by high-angle boundaries into elongated subgrains (~ 100 nm). It was shown with in-situ annealing experiments in the TEM that this microstructure is thermally stable up to a temperature of 450° C. Tensile tests showed that the combination of ECAP with CR has the potential to produce at the same time high strength (941 MPa) and high ductility (16.7%).
Mechanical Properties of ECAP Processed Magnesium Alloy AS21X
Authors: Lamark T.T. , Hellmig Ralph Jörg , Estrin Yuri
Published: March 2009

Typically, magnesium alloys with conventional grain size exhibit microplastic behaviour already at low stresses. This behaviour restricts the technological utilization of these materials. The aim of this study was to investigate whether ECAP can be applied to enlarge the elastic range of AS21X. Cyclic tensile tests at room temperature were carried out to examine the effect of the ECAP induced grain refinement on the elastic properties. The results obtained are compared with the cyclic behaviour of conventional, coarse-grained AS21X. The differences in mechanical properties between the two conditions are discussed.
Annealing Behavior and Recrystallized Texture in ARB Processed Copper
Authors: Takata Naoki , Yamada Kousuke , Ikeda Kenichi , Yoshida Fuyuki , Nakashima Hideharu , Tsuji Nobuhiro
Published: March 2009

The recrystallization behavior and texture development in copper accumulative roll-bonding (ARB) processed by various cycles (2, 4 and 6 cycle) were studied by differential scanning calorimetry (DSC) analysis and SEM/EBSP method. The exothermic peaks caused by recrystallization appeared at 210 ~ 253 in each sample. The peak positions shifted to lower temperature as the number of ARB cycles increased. This result indicated that the evolution of finer microstructure with increasing number of the ARB cycles enhanced the occurrence of recrystallization at lower temperature. The stored energy calculated from the DSC curve of the ARB processed copper increased with the increasing strains. During an annealing, the preferential growth of cube-oriented grains ({100}<001>) occurred in each sample. The recystallization behavior of ARB processed copper having low stacking fault energies was distinguished from that of so-called “recovery type” materials, i.e. aluminum and low carbon steels, which shows rather continuous changes in microstructure during annealing. The accumulated strains provided the driving force for the preferential growth, which was the same mechanism as the preferential growth in normally rolled copper. The sharpest cube texture developed in ARB processed copper by 4 cycles. The difference of cube texture development between 2 cycles and 4 cycles was caused by the distribution of cube-oriented regions which corresponded to the nucleation sites of recrystallized grains before annealing. More nanocystalline layers in the vicinity of bonded interfaces were distributed in ARB processed copper by 6 cycles than 4cycles. The nanocystalline structure could grow faster than the cube-oriented grains and led to the inhibition of sharp cube texture in the ARB processed copper by 6 cycles.
Grain Boundary Structure in ARB Processed Copper
Authors: Ikeda Kenichi , Takata Naoki , Yamada Kousuke , Yoshida Fuyuki , Nakashima Hideharu , Tsuji Nobuhiro
Published: March 2009

Grain boundary structures in the Accumulative roll-bonding (ARB) processed copper (ARB-Cu) have been studied. The grain boundary structures were observed by high-resolution transmission electron microscopy (HRTEM). In order to clarify the difference between the grain boundaries in ARB-Cu and equilibrium boundaries, calculated atomic structure of symmetric tilt grain boundaries with <110> common axis (<110> symmetric tilt grain boundary; <110> STGB) in Cu were used. The near 14° boundary in the ARB-Cu could be described by the dislocation model, but the dense dislocation region existed near the grain boundary. The high angle boundaries in ARB-Cu could be described by the structural units which were obtained by molecular dynamics (MD) simulation. Furthermore, in the 2 cycles and 6 cycles ARB-Cu (2cARB-Cu and 6cARB-Cu), the deformation twin boundaries could be observed and described by the structural unit. Therefore, it was concluded that the grain boundary structure in the ARB-Cu was not much different from the normal equilibrium grain boundary and explained by conventional dislocation and structural unit models.
Hardening Mechanisms of Metals and Alloys Produced by SPD
Authors: Hashimoto Satoshi , Suzuki T. , Vinogradov Alexei
Published: March 2009

Strengthening is a complex process involving such basic mechanisms as dislocation accumulation (work hardening), Hall-Petch hardening due to grain refinement, solid solution hardening and precipitation hardening in various combinations. The contribution of different mechanisms into resultant strength can vary significantly depending on chemical composition and processing. The purpose of the present work is to explore the significance of SPD for hardening and to clarify the role of different strengthening mechanisms. The model Au-based system was employed using pure Au, single phase solid solution Au-25Ag and precipitation hardenable Au-12.5Ag-12.5Cu (in mass %) alloy subjected to ECAP. The additive character of different strengthening mechanisms is clearly demonstrated. The extremely high strength exceeding 1 GPa is achieved in the Au-Ag-Cu after ECAP followed by aging, which has never been attained in conventional processing schemes.
Droplet Formation Studies for a Piezo-Actuated Micro-Injector
Authors: Yang An Shik , Cheng Chiang Ho , Tsai Wei Ming , Hsu Fu Chiang
Published: March 2009

The droplet formation process of a novel piezo-actuated micro-injector is studied using a computational approach. In simulations, the theoretical model is based on the time-dependent threedimensional conservation equations of mass and momentum. The surface tension effect at the gasliquid boundary is treated using the continuous surface force (CSF) scheme. The volume-of-fluid (VOF) method in conjunction with the piecewise linear interface construction (PLIC) technique is
exploited to describe interfacial movements. The time evolution of the droplet meniscus shape is predicted throughout the formation process and compared with Shield's micro-photographed images for the computer package validation. To explore the feasibility of proposed new micro-injector in practical applications, the droplet deformation characteristics are determined in terms of droplet
topology, breakup length and time, and flight velocity for dispensing different liquids such as water, anisol, Pedot, PLED, and blood.
Development of a Virtual Controller Integrating Virtual and Physical CNC
Authors: Kao Yung Chou , Chen Hong Ying , Chen Y.C.
Published: March 2009

This paper describes the development of a virtual CNC controller. Controller is the major driver for a CNC machine. Similarly, virtual controller is the key driving component for a virtual CNC, which is a three-dimensional digitized physical CNC. A virtual CNC can exist in every PC serving as the complementary safer counterpart in lecturing and learning the hand on operation of expensive machinery such as five-axis milling machine, high speed CNC and mill-turn because the
virtual CNC will not break. Virtual reality environment provided by EON studio software has been adopted in establishing the interactivity of a virtual CNC based on the geometry model constructed in off-the-shelf CAD software. Visual Basic was used in implementing the graphical user interface to operate the virtual CNC through the developed virtual controller. The virtual controller is in charge of
(1) parsing user’s NC codes, (2) simulating the tool path of the parsed NC codes, and (3)driving the virtual CNC according to the tool path. The developed virtual CNC controller has been successfully applied in implementing virtual CNCs based on two physical three-axis CNC machines and has also
been demonstrated in an international exposition successfully. The virtual controller can enable the virtual CNC in facilitating lecturing, tutoring, self-learning, and reducing the chances of accidental breakdown of precious CNC equipment.
MICAST – Microstructure Formation in Casting of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions
Authors: Ratke Lorenz , Steinbach Sonja , Müller Georg , Hainke Marc , Roósz András , Fautrelle Yves , Dupouy M.D. , Zimmermann Gerhard , Weiß A. , Diepers Hermann-Josef , Lacaze Jacques , Valdes R. , Grün G.U. , Nicolai H.-P. , Gerke-Cantow H.
Published: March 2009

The MICAST research program focuses on a systematic analysis of the effect of convection on the microstructure evolution in cast Al-alloys. The experiments of the MICAST team are carried out under well defined thermally and magnetically controlled, convective boundary conditions and analyzed using advanced diagnostics and theoretical modeling, involving phase field simulation, micro-modeling and global simulation of heat and mass transport. The MICAST team uses binary, ternary and technical alloys of the Al-Si family. This paper gives an overview on recent experimental results and theoretical modelling of the MICAST team.
Control of the Macrosegregations during Solidification of a Binary Alloy by Means of a AC Magnetic Field
Authors: Wang Xiao Dong , Ciobanas A. , Baltaretu Florin , Bianchi Anne Marie , Fautrelle Yves
Published: March 2009

A numerical model aimed at simulating the segregations during the columnar
solidification of a binary alloy is used to investigate the effects of a forced convection. Our objective is to study how the segregation characteristics in the mushy zone are influenced by laminar flows driven both by buoyancy and by AC fields of moderate intensity. Various types of magnetic fields have been tested, namely travelling, rotating magnetic field and slowly modulated electromagnetic
forces. The calculations have been achieved on two types of alloys, namely tin-lead and aluminiumsilicon. It is shown that the flow configuration changes the segregation pattern. The change comes from the coupling between the liquid flow and the top of the mushy zone via the pressure distribution along the solidification front. The pressure difference along the front drives a mush flow, which transports the solute in the mushy region. Another interesting type of travelling magnetic field has
been tested. It consists of a slowly modulated travelling magnetic field. It is shown that in a certain range of values of the modulation period, the channels are almost suppressed. The normal macrosegregation remains, but the averaged segregation in the mushy zone is weaker than in the natural convection case. The optimal period depends on the electromagnetic force strength as well as the cooling rate. The latter phenomenon cannot occur in the case of rotating magnetic fields, since in
that configuration the sign of the pressure gradient along the solidification front remains unchanged. Recent solidification experiments with electromagnetic stirring confirm the predicted macrosegregation patterns.
Motion of Fine Particles under Interfacial Tension Gradient in Relation to Solidification of Steel
Authors: Mukai Kusuhiro , Zeze Masafumi , Morohoshi Takashi
Published: March 2009

It is important to understand the behavior of argon gas bubbles and non-metallic
inclusions in front of the solidifying shell in order to improve the surface quality of steel products, in the steelmaking industry. Based on a series of fundamental researches on the motion of fine particles under the interfacial tension gradient, Mukai and Lin [1] proposed a new mechanism wherein the solute concentration gradient in front of the solidifying shell, which is the interfacial
tension gradient between liquid steel and particles, plays an important role in the entrapment of argon gas bubbles and non-metallic inclusions by the solidifying shell in continuous casting of steel. Developing this idea, this paper proposes Mukai-value M for use in estimating the dependence of the interfacial gradient force required to entrap the particles on solute concentrations of steel. Use of this index enables rapid quantitative prediction of the behavior of argon gas bubbles and
non-metallic inclusions in the continuous casting of steel.
Estimation of the Cooling Rate on the Basis of Secondary Dendrite Arm Spacing in Case of Continuous Cast Steel Slab
Authors: Hoó Csaba , Teleszky Ilona , Roósz András , Csepeli Zsolt
Published: March 2009

The different solidification processes occuring in steels can be well studied by using the microstructure investigation. The microstructure can be observed after the sample preparation by using a special type of Oberhoffer etching. The changes in the cooling rate can be described by determining the secondary dendrite arm spacing. A relative cooling rate can be calculated by applying the relationship between the secondary dendrite arm spacing and the cooling rate which characterises the changes of cooling conditions in the ingot during the solidification..
Monotectic Growth: Unanswered Questions
Authors: Andrews J.B. , Downs D.A. , Liu Qing Quan
Published: March 2009

Early solidification experiments in immiscible alloy systems almost immediately led to
conflicting findings between investigators. Investigations revealed that several factors usually considered unimportant, especially the interfacial energy relationships between phases, could have a dramatic influence on the types of microstructures produced in immiscible alloy systems. During the 1980s, work concentrated on the influence interfacial energy on microstructure. However, some
findings raised new questions. In the mid 1990s and continuing through today, most efforts have focused on modeling the monotectic growth process and on obtaining steady state coupled growth conditions in hypermonotectic alloys. This paper focuses on some of the advances that have been made to date in understanding solidification in immiscible alloy systems and some of the questions that remain to be answered.
New Algorithm to Calculate Liquid – Solid Shrinkage and Graphite Expansion
Authors: Weiß K. , Honsel Christoph
Published: March 2009

Meanwhile the calculation of cooling and solidification is a well introduced tool into the
foundry industry for calculating gating and riser systems. However, knowing the areas of last solidification is often no answer to the question if there are any defects in the casting or not. Of course one requirement is an exact description of the heat flow and the heat transfer between melt and mould. But furthermore the liquid/liquid and liquid/solid shrinkage influence the temperature fields due to a convective heat flux. Also auxiliary material influence the liquid/solid behaviour. Auxiliary materials can be on one hand the inoculation material and on the other chills with and without coating. This is the reason, why defects near the gating often can not be detected by a conventional solidification calculation, which doesn’t take into account the impact of the auxiliary material on the convective flow. With new algorithms within the FEM program SIMTEC/WinCast it is possible to respect this behaviour during the simulation of solidification. Special attention was turned to the expansion of graphite in ductile irons. The graphite first nucleates in the liquid, and then continues to grow in the solid phase depending on the alloy compositions and the solidification parameters. With the knowledge about the physical properties of the alloy the location and the size of defects can be predicted precisely.
Calculation of the Equilibrium Phase Diagram of Fe-Ni Alloy System by the ESTPHAD Method
Authors: Kövér Zsuzsanna , Roósz András
Published: March 2009

Including detailed information of equilibrium phase diagrams (EPhD) is is one of the
necessary features in phase transformation simulations. It is important for a simulation to provide a simple but accurate EPhD calculation method which is based on the knowledge of the phase boundary lines in the EPhDs as an mathematical function. A simple, fast and iteration free approximate calculation method has been developed earlier (ESTPHAD – Estimated Phase
Diagrams). The input data may be either experimental values, or a data field calculated by CALPHAD, or digitized data from the graphical representation of measured and published EPhDs . By this method important parameters such as the beginning and ending temperatures of solidification or solid state transformations can be determined for each phase. The partition ratios as a function of the concentration can be calculated as well. In this study ESTPHAD is used to
estimate the EPhD of binary Fe-Ni system.
Determination of Al Site Preference in L12 TiZn3 - Base Trialuminides
Authors: Krajewski Witold K.
Published: March 2009

The atoms site preference in the Al3Ti-Zn system has been studied using H. Rietveld method. The L12 Ti(Al, Zn)3particles evolve in a ZnAl25 melt from the L12TiZn3particles in the ZnTi4 master alloy. It is found that Zn is replaced by Al during the transformation TiZn3→ Ti(Al, Zn)3. In the evolving fcc L12 Ti(Al, Zn)3phase Ti occupies (0, 0, 0) position while Al and Zn occupy (0, 0.5, 0.5) position, similarly to Al and X in the Al3Ti-X systems, where X = Ni, Cr, Mn, Cu, Ag, Pd [1, 2].
Calculation of the Liquidus and Solidus Surface of Al Rich Corner of Al-Mg-Si Alloy System by ESTPHAD Method
Authors: Farkas János , Roósz András
Published: March 2009

A simple but thermodinamically well-founded method is described for the recalculation
of liquidus surfaces and partition coefficients of multicomponent equilibrium phase diagrams used a data file of the liquidus temperature and partition coefficients calculated by CALPHAD method. The applicability of the method is shown in case of Al-Mg-Si ternary alloy systems.
On a Morphological Transition in Monotectic Solidification
Authors: Müller Anja , Ratke Lorenz
Published: March 2009

Al-Bi and Al-In of exact monotectic composition were directionally solidified with solidification velocities ranging from 0.3 µm/sec to 5 µm/sec and temperature gradients from 2 K/mm to 6.5 K/mm. Three distinct microstuctures could be observed: fibers, strings of pearls or irregular arrays of second phase droplets. The transitions from fibers to strings of pearls is discussed theoretically and compared with the experimental results. The origin of this transition seems to be a Nichols and Mullins instability of the fibers during cooling from the monotectic to the eutectic temperature caused by surface perturbations driving volume diffusion of solute in the liquid fibers of the second phase.
Nanocrystalline Intermetallic Mg2Ni Produced in a Batch Scale Mill
Authors: Martínez-Franco E. , Klassen Thomas , Bormann Rüdiger , Jaramillo-Vigueras D.
Published: March 2009

Nanocrystalline intermetallic Mg2Ni is successfully produced on a batch production scale from elemental powder blends by mechanical alloying using a high-energy rotor ball mill (Simoloyer). Different ball-to-powder mass ratios are used in order to provide results for scaling to industrial production. Transformation of elemental Mg-Ni powders into the Mg2Ni intermetallic is observed by x-ray diffraction. Particle morphology during milling is observed by scanning electron microscopy. A relatively low Fe contamination is estimated by energy dispersive spectrometry.
Thermal Analysis and Evolution of Phases during the Synthesis of Cordierite with Kyanite and Talc
Authors: Vernet-Patiño Iván , Balmori-Ramírez Heberto , Bradt Richard C.
Published: March 2009

Cordierite has been synthesized by heating mixtures of kyanite and talc, using kyanite powders of two different sizes. The reaction is studied by thermogravimetric and differential thermal analysis. Phase changes are followed by X-Ray diffraction of samples fired between 750 °C and 1400 °C. The evolution of the reaction starts with the dehydration of talc at approximately 880 °C. The kyanite decomposes at approximately 1140 °C. The first traces of α-cordierite appear at around 1200 °C. The influence of the kyanite particle size on the kinetics and microstructure is
analyzed.
Direct Extrusion Production of Monolithic Ceramics with Different Cross Section
Authors: Rocha-Rangel Enrique , Moreno-Guerrero M.S. , Hernández R.T. , Rodríguez M.
Published: March 2009

The present work describes the fabrication of monolithic ceramics of different geometries through direct extrusion of ceramic pastes. Using this technique, ceramic rods with triangular, hexagonal, honey-like and tubular cross sections have been produced. The shape of some of these monolithic materials allows piling them up for building big catalytic reactors. After extruding and sintering, all processed ceramics have appropriate characteristics such as homogeneous texture, and controlled density and porosity. These results suggest the feasibility of using the extruded ceramics for different catalysis and filtering applications. Some features of the monolithic ceramics and the fabrication process will be analyzed.
The Effect of Hot Rolling on Room Temperature Ductility of a NiAl Intermetallic Compound
Authors: Garcia-Galan Sergio , Aramburo-Perez Gerardo , González-Rivera Carlos , Herrera R. , Juárez-Islas J.A.
Published: March 2009

A Ni57Fe18Al25 alloy is produced by vacuum induction melting under an argon
atmosphere and gravity cast into a copper chill mould. Ingots of 2 x 10 x 50 mm are re-heated at 1100 °C for 24 hours and hot rolled until a 25 % reduction is reached. Immediately, hot rolled plates are heat treated at 1100 °C for 1 hour and water cooled to room temperature. Microstructures of as cast, hot rolled and hot rolled plus heat treated specimens are characterized using scanning and
transmission electron microscopy and x-ray diffraction. Specimens in the as-cast and hot rolled conditions show the presence of equiaxial and partially elongated β-grains, respectively, with the presence of a thin γ-phase decorating the grain boundaries. Hot rolled plus heat treated specimens have partially recrystallized β-grains with γ-phase and (Ni,Fe)3Al at the grain boundaries. The hot
rolled specimens have a room temperature ductility of approximately 5 % in tensile testing. This enhancement in ductility is attributed to the modification of the β-grains by coexistence with a γ- phase along the grain boundaries.
Mechanical Properties and Machinability of Si3N4/hBN Composites Prepared by Pressureless Sintering
Authors: Cho Won Seung , Lee Ki Ju , Cho Myeong Woo , Lee Jae Hyung , Hwang Woon Suk
Published: March 2009

The effects of hBN content on microstructure, mechanical properties, and machinability of the pressureless-sintered Si3N4 ceramics were investigated. Flexural strength, Young’s modulus, and hardness decreased with increasing h-BN content. The mechanical properties are decreased mainly because of increased porosity of composite, and the much lower Young's modulus of BN
compared to that of Si3N4. Pressureless-sintered Si3N4/hBN composites exhibit strong texture of BN grains oriented with the c-axis parallel to the cold-pressing direction. Cutting resistance of Si3N4 ceramic composites with more than 10 vol% hBN decreased with increasing hBN content, demonstrating a good machinability of the composites. The residual pores can be attributed to improved machinability of pessureless-sintered Si3N4-BN composite.
Microstructure and Electrical Properties of R.F Magnetron Sputtering Derived PZT Thin Films Deposited on Interlayer for Pyroelectric IR Sensor
Authors: Park Chul Ho , Son Young Gook
Published: March 2009

The PZT thin film was deposited by R.F. Magnetron sputtering with Pb 1.1Zr0.53Ti0.47O3 target. When interlayers were inserted at the between PZT and Pt, The grain growth of the PZT thin films was considerably improved by various interlayers (PbO, TiO2, TiO2/PbO) and had low-processing temperature. Compared to the pure PZT thin films, pyroelectric properties of the PZT thin films inserted by interlayers were relatively measured high value. In particular, PZT thin film deposited on interlayer(PbO) was appeared the best pyroelectric properties (P=189.4μ C/㎠K, FD=12.7×10-6Pa-1/2, FV=0.018㎡/C) respectively. As a result of XPS depth profile analysis, both PZT thin film and interlayers were confirmed as independently existing layer respectively.
The Effect of Tungsten Content on Nanocrystalline Structure of Ni-W Alloy Electrodeposits
Authors: Hwang Woon Suk , Cho Won Seung
Published: March 2009

The effects of tungsten content on the nanocrystalline structure of Ni-W alloy
electrodeposits were investigated. Direct current electrodeposition was conducted with various W mole fractions in a nickel sulfate solution containing citric acid as a complexing agent. Current efficiency was an almost constant value of 52% up to W mole fraction of 0.58. However, it was sharply decreased owing to severe H2 evolution with increasing cathode overvoltage at a W mole fraction higher than 0.74. The X-ray diffraction peak was decreased and broadened with increasing
W content, and an amorphous pattern appeared clearly at 49 wt.% W. It was confirmed that Ni-W alloy deposit was transformed from crystalline to amorphous structure between 41 and 49 wt.% W. This result was also verified through a TEM analysis.
Effects on the Carbon Matrix as Conductor in Sulfur Electrode for Lithium/Sulfur Battery
Authors: Choi Young Jin , Jeong Sang Sik , Kim Ki Won , Ahn Hyo Jun , Ahn Jou Hyeon
Published: March 2009

Lithium/sulfur battery has some problems such as low utilization of active material and
poor cycle life owing to the dissolution of lithium polysulfide into electrolyte, aggregation of sulfur during charge-discharge process, and structural change of sulfur electrode. To overcome such problems, carbon nano tubes (CNTs) and graphitic nano fibers (GNFs) were added into the sulfur electrode. The addition of CNTs and GNFs having a network-like structure is expected to offer the
structural stability and good electrical path of sulfur electrode. The morphology of fabricated sulfur electrode was observed by using scanning electron microscope (SEM), and the crystalline structure was characterized by using X-ray diffraction (XRD). The charge/discharge tests were conducted in
the voltage range 3.2/1.5V (vs.Li) with a galvanostatic method.
Characterization of Electrical Properties of Si Nanocrystals Embedded in an Insulating Layer by Scanning Probe Microscopy
Authors: Kim Jung Min , Her Hyun Jung , Son Jeong Min , Khang Y. , Lee Eun Hye , Kim Yong Sang , Choi Y.J. , Kang C.J.
Published: March 2009

Scanning probe microscope (SPM) with a conducting tip was used to electrically probe silicon nanocrystals (Si NCs) embedded in a SiO2 layer. The Si NCs were generated by the laser ablation method with compressed Si powder followed by a sharpening oxidation. The size of Si NCs is in the range of 10-50 nm, and the density is around 1011 /cm2. Using a conducting tip, the charge was injected directly into each Si NC, and the image contrast change and dC/dV curve shift
caused by the trapped charges were monitored. The results were compared with those of the conventional MOS capacitor.
The Effects of Si Addition to the Tin Oxide Thin Films on the Electrochemical Characteristics for Lithium Secondary Microbattery Anode
Authors: Park Chul Ho , Son Young Gook
Published: March 2009

For lithium secondary microbattery anode, the tin oxide thin films with the various Si
additions (0, 2, 6, 10, 20mol%) were prepared on the p-type (100) SiO2/Si substrate by R.F. magnetron sputtering method at the substrate temperature of 300°C under the gas ratio of Ar/O2 (7/3). The effect of Si addition to the SnO2 thin film on the structural change and electrochemical performance and the reversible capacity performance was investigated. As Si addition amounts increased, Si-O bonding density increased and Sn-O bonding density decreased. The addition of
optimum Si amount led decrease of Sn oxidation state so that the irreversible capacity was reduced and cycle characteristic was enhanced during the charge-discharge test. SnO2 films with 6mol%Si had the highest reversible capacity of 700mAh/g after 100cycles.
Effects of Deformation on Atmospheric Corrosion of Galvanized Steel
Authors: Choi Jae Woong , Hwang Gil Ho , Cha Hong Rae , Kang Sung Goon
Published: March 2009

The effects of deformation on corrosion behavior of galvanized steel were investigated. Accelerated corrosion test was conducted under the conditions of 30oC and 90% relative humidity with flowing 200ppm sulfur dioxide gas for five weeks. Surface morphologies and corrosion products were analyzed by SEM/EDS and XRD. The corrosion products were composed of hydrates of ZnSO4. And corrosion rates of each part, bottom, bended and wall, were increased with
growing strain due to surface damage and enlargement of naked surface for corrosion.
Appearance of Indium Oxide Nanorods in MOCVD Growth
Authors: Myung Ju Hyun , Kim Hyoun Woo , Shim S.H.
Published: March 2009

We report on the first synthesis of nanosized In2O3 rods using the TEI as a precursor in the presence of oxygen. The samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy. XRD analysis revealed that the products are In2O3 phase with a tetragonal cubic structure. SEM analysis indicated that the
obtained nanorods have a circular cross section and a diameter in the range of 50-150 nm.
Effects of Current Density on the Formation of Anodic Oxide Films on AZ91
Authors: Kim Seong Jong , Kim Jeong Il
Published: March 2009

Magnesium must be surface treated to prevent corrosion, since it is a very active metal electrochemically. On anodizing, a compact film several tens of micrometers thick forms on magnesium, which imparts good corrosion resistance. The Mg-Al alloy (AZ91) was anodized in 1 M NaOH solution. The surface morphology of the anodized films was observed using scanning electron microscopy (SEM), energy-dispersive x-ray (EDX), and electrochemical methods. The effects of current density on the formation of anodic oxide films for a Mg-Al alloy in 1 M NaOH
were investigated. In the anodic polarization curve, the reference corrosion potentials were far greater at 4-9 mA/cm2 than at 1 mA/cm2. The film that formed at 1 mA/cm2 was thin, suggesting that parts of the film had been dissolved or destroyed during the anodic polarization test. Corrosion resistance differed owing to concentric differences in current flow. Thick anodic oxide films were formed at higher applied currents.
Nitride Formation on Titanium under Irradiation of Intense Pulsed Ion Beam
Authors: Zhu X.P. , Suzuki Tsuneo , Suematsu Hisayuki , Jiang Wei Hua , Niihara Koichi
Published: March 2009

Nitriding of titanium was achieved in a vacuum of ~2×10-2 Pa by applying intense pulsed ion beam (IPIB) irradiation. Various phases including ‘pure’ nitrides (e.g. Ti2N, TiN) as well as carbonitrides (e.g. TiC0.3N0.7) were found on the IPIB-irradiated surfaces that depended on the ion beam intensity, shot number, and sample position with respect to the ion beam axis. It was found that the nitrides were preferably produced at moderate beam intensity by which the nitriding depth
increased greatly with multi-shot irradiation. No or less nitrides were produced under irradiation of very high intensity or less number of shots. It is demonstrated that the IPIB nitriding process is very efficient even in vacuum where the residual N2 can readily react with melted Ti surfaces under IPIB irradiation. The origin of incorporated C in the nitrides is mainly attributed to the anode material of
ion diode used in the IPIB apparatus.