bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Protection of the Steel Sheet with Zn-Fe Alloys
Authors: Radu Tamara , Ciocan A. , Balint L. , Mitoseriu O.
Published: January 2010

The Zn-Fe layers are recommended in automotive industry and in the adders for the following qualities: a better weldability than the zinc-coated plates, very good capacities for painting and lacquer wear resistance, good adherence, lower zinc consumption by layer thickness below 100g/m2. Important transformation of phases takes place during heating of galvanized parts due to mass transfer iron in the zinc layer and Zn-Fe alloy is formed. Galvanized steel samples were heated 10-30 sec. at 500-650oC. Heat treated samples were metallographic ally examined and X- ray diffraction tested with a view to establish structural and chemical composition change due to heat treatment. As a result of microscopic examination (both optical and electronic) and X-ray diffraction testing in coating layer were detected phase ratio changes, according to heat treatment parameters. Considering that the physico-chemical and mechanical properties differ for the two phases and phase ratio is to decide the properties of the product; these structural changes are of great importance in practice. The desirable coating would be a Zn-Fe coating with 8-10% Fe (according to some authors, up to 12% Fe), with a structure consisting mainly of  phase and a small quantity of  phase. The mathematical correlation between diffusion phenomena occurring in layer, depending on temperature and time of heat treatment, and iron content of coating are presented.
Corrosion Protective Properties of Hydrotalcites Doped Hybrid Sol-Gel Coatings on Aluminium Substrates
Authors: Álvarez D. , Collazo A. , Hernández Miguel , Nóvoa Xosé R. , Pérez C.
Published: January 2010

Hydrotalcite-like compound that belongs to anionic clay family was prepared by classical co-precipitation method using magnesium and aluminium nitrates as precursors. Different weight percentages of hydrotalcite with Mg/Al ratio of 2.5 was added (1, 5 and 10 % wt.) to hybrid sols prepared by copolymerization of 3-Glycydoxypropyltrimethoxysilane (GPTMS) and tetra-n-propoxyzirconium (TPOZ). The aim of this work was to study the effect of the hydrotalcite incorporation to hybrid sol-gel coatings on aluminium alloys as substitution of chromate inhibitors. Hybrid sol-gel coatings were deposited by dip coating method on AA2024-T3 substrates. By Scanning Electron Microscopy (SEM) and mechanic profilometry it was possible to see the distribution of HTCP agglomerates which varies from nanometres to micrometers. The corrosion performance was evaluated by the accelerated test salt fog spray chamber (SSFC) and by Electrochemical Impedance Spectroscopy (EIS). The obtained results show the corrosion resistance improvement at higher weight percentages of HTCP.
Explosively Driven Expansion and Fragmentation Behavior for Cylinders, Spheres and Rings of 304 Stainless Steel
Authors: Hiroe Tetsuyuki , Fujiwara Kazuhito , Hata Hidehiro , Yamauchi Mitsuru , Tsutsumi Kiyotaka , Igawa Takuya
Published: January 2010

Explosive loading techniques are applied to expand tubular cylinders, spherical shells and rings of 304 stainless steel to fragmentation, and the effects of wall thicknesses, explosive driver diameters and the constant proportionality of the in-plane biaxial stretching rates are investigated on the deformation and fracture behavior of three basic structures experimentally and numerically. In the cylinder tests, the driver is a column of high explosive PETN, inserted coaxially into the bore of a cylinder and initiated by exploding a fine wire bundle at the column axis using a discharge current from a high-voltage capacitor bank. In case of the ring tests, ring specimens are placed onto a single cylinder filled with the PETN as a expansion driver, and for sphere tests, specimens filled with the PETN are also initiated by exploding a fine copper wire line with small length located at the central point. Two types of experiments are conducted for every specimen and test condition. The first type uses high speed cameras to observe the deformation and crack generation of expanding specimens showing the final maximum in-plane stretching rate of above , and the second uses soft capturing system recovering typically most fragments successfully. The fragments are measured and investigated using a fragmentation model. The effects of test parameters on the deformation and fracture behavior for three types of structures are discussed in need of modified fragmentation model for shell structural elements.
Some Trials on Underwater Explosive Welding of Thin W Plate onto Copper Substrate
Authors: Hokamoto Kazuyuki , Manikandan Palavesamuthu , Mori Akihisa
Published: January 2010

The possibility of the use of underwater shock wave to weld a thin plate onto a base plate is demonstrated in the present investigation. The composite materials of tungsten and copper have been used for many applications such as high heat flux components, welding electrodes, electrical contacts at high voltage and heat sink. In this work, thin tungsten plate was tried to weld on a copper base plate using underwater explosive welding technique which has been developed by one of the authors’ group. This technique enables to accelerate a thin plate to several hundreds m/s to satisfy the condition of explosive welding. Such an order of the velocity is adequate to form welding at the interface. In the case of the use of underwater shock wave derived from the detonation of an explosive in water, the kinetic energy required for the welding is appropriate and it makes possible to suppress the effect of heating which may induce excessive melting and/or form brittle intermetallics at the interface. The welding interface showed wavy structure typically found in explosively welded materials and the bonding strength is expected to be high as the clads explosively welded by conventional method. The effect of experimental parameters on the interfacial microstructure is discussed.
In Situ Observation of Grain Growth and Recrystallization of Steel at High Temperature
Authors: Yogo Yasuhiro , Tanaka Kouji , Nakanishi Koukichi
Published: January 2010

An in-situ observation method for structures at high temperature is developed. The new observation device can reveal grain boundaries at high temperature and enables dynamic observation of these boundaries. Grain growth while maintaining microstructure at high temperature is observed by the new observation device with only one specimen for the entire observation, and grain sizes are quantified. The quantifying process reveals two advantages particular to the use of the new observation device: (1) the ability to quantify grain sizes of specified sizes and (2) the results of average grain size for many grains have significantly less errors because the initial structure is the same for the entire observation and the quantifying process. The new observation device has the function to deform a specimen while observing structures at high temperature, so that enables it to observe dynamic recrystallization of steel. The possibility to observe recrystallization is also shown.
Advanced Bainitic and Martensitic Steels with Carbide-Free Microstructures Containing Retained Austenite
Authors: Edmonds D.V.
Published: January 2010

Recent decades have witnessed some remarkable advances in engineering steels driven by the need to respond to challenges posed, for example, by recovery and transmission of oil and gas, or enhanced vehicle safety and fuel economy. Foremost amongst these must surely be the extended application of carbon steels, achieved principally through ferrite grain refinement by the practice of microalloying coupled with controlled thermomechanical processing. Limitations to strengthening ferrite/pearlite structures further by grain refinement or precipitation, however, has focused attention back to acicular forms of microstructure. One of the most interesting advances in this area has been the development of bainitic steels, which have been almost dormant since the mid-20th century. This resurgence may partly be attributed to a better appreciation of the bainite transformation mechanism, and the experimental work for this which unexpectedly spawned some interesting bainitic microstructures which have seen further development and application. These are the so-called ‘carbide-free’ bainites, which employ alloying to replace carbides, principally cementite, with carbon-stabilized retained austenite. Particularly noteworthy has been the emergence of the transformation induced plasticity (TRIP) sheet steels with enhanced properties principally targeted for automotive use. It is worth mentioning also that a parallel development has produced similar microstructure in austempered ductile irons (ADI), another important ferrous alloy which has seen recent expanding interest in its application. Even more recently, as we proceed into the 21st century, the concept of employing steel microstructures containing carbon-enriched retained austenite, has been developed further by combining both alloying and novel heat treatment procedures to exchange ‘bainitic’ ferrite with ‘martensitic’ ferrite. Interestingly, this non-equilibrium ‘quenching and partitioning’ process route also offers the possibility to increase the retained austenite carbon concentration to very high levels, potentially revealing new and previously unobtainable properties.
Improvement of DMFC Electrode Kinetics by Using Nanohorns Catalyst Support
Authors: Brandão L. , Mirabile Gattia Daniele , Marazzi Renzo , Vittori Antisari Marco , Licoccia S. , d’Epifanio A. , Traversa Enrico , Mendes A.
Published: January 2010

One of the factors limiting direct methanol fuel cells (DMFC) performance is the slow kinetics of methanol oxidation at the anode. The importance of the catalyst support for fuel cells has been recognized and different forms of carbon have been suggested. Single wall nanohorns (SWNH) are a new class of carbon with a similar graphitic structure of carbon nanotubes. They are self-assembling materials that produce aggregates of about 100 nm. In the present study, the comparison of the performance of a DMFC equipped with electrocatalysts supported on a commercial carbon black and on SWNH was carried out. The SWNH were synthesized by the arc discharge method in air. The deposition of the Pt and Pt/Ru catalysts on the carbon supports was accomplished by using ethylene glycol as reducing agent. The synthesized catalyst nanoparticles have a very small diameter size (ca. 2.5 nm) and they are uniformly distributed on both carbon supports. The supported electrode catalysts were tested in a DMFC and results indicate that employing SWNH is very promising showing catalytic activities 60 % higher.
Ni-Fe-LaGaO3 Based Alloy Anode Cermet for Direct Hydrocarbon Type Solid Oxide Fuel Cell Using LaGaO3 Electrolyte
Authors: Zhong Hao , Ishihara Tatsumi , Matsumoto Hiroshige
Published: January 2010

Cermet anode of NiFe(9:1)-La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) (90:10 weight ratio) was studied for direct CH4 fueled SOFC operating at intermediate temperature. In case of NiFe bimetal anode, power density of the cell decreased drastically after operation under CH4 feeding condition. On the other hand, mixing Sm doped CeO2, MgO, or LSGM is effective for improving the long term stability. The cell with NiFe-LSGM anode exhibited much stable power density under CH4 feeding condition. Deposition of coke was also studied by Raman spectroscopy and no coke deposition was observed after 15 h operation. Since the surface activity of this anode is high, power density was hardly dependent on PCH4.It was found that NiFe-LSGM10 shows a high tolerance against the coke deposition under CH4 feeding condition.
Hydrogen Diffusion Coefficient, Hydrogen Solution Coefficient and Hydrogen Permeability of Nb-TiNi Eutectic Alloy
Authors: Wang Wei Liang , Ishikawa Kazuhiro , Aoki Kiyoshi
Published: January 2010

In general, hydrogen permeabilityΦ of the alloy membrane is expressed as the product of the hydrogen diffusion coefficient D and the hydrogen solution coefficient K. Therefore, to improve the hydrogen permeability efficiently, the values of K and D should be separately considered. In the present study, hydrogen absorption and permeation behaviors of the Nb19Ti40Ni41 alloy consisting of the eutectic phase are investigated by measuring pressure-composition-isotherm (PCI) and by the hydrogen flow method and compared with those of palladium. The hydrogen absorption in the Nb19Ti40Ni41 alloy does not obey the Sieverts’ law in the pressure region of 0-1.0MPa at 523K, but it shows linear relationship between the difference in the square root of hydrogen pressure and hydrogen content between 0.1 and 0.4MPa. Although the value of D for the Nb19Ti40Ni41 alloy is considerably lower than that of palladium, its high K value enhances the hydrogen permeability Φ. It is suggested that the enhancement of D by microstructural control for Nb19Ti40Ni41 alloy is effective for improvement of Φ.
Micro/Nano-Structures and Hydrogen Absorption/Desorption Properties of Mg/Cu Super-Laminates
Authors: Tanaka Koji , Kiyobayashi Tetsu , Takeichi Nobuhiko , Miyamura Hiroshi , Kikuchi Shiomi
Published: January 2010

Super-laminates have been attracting attention since co-authors Ueda et al. reported that Mg/Cu super-laminates showed reversible hydrogenation and dehydrogenation at 473K. The Mg/Cu super-laminates were prepared by a repetitive fold and roll method. Initial activation at 573 K led the super-laminates to absorb hydrogen at 473K. TEM observations of micro/nano-structures in the Mg/Cu super-laminates and Mg2Cu powder were performed in order to clarify the process of hydrogenation and dehydrogenation at 473K. The as-rolled Mg/Cu super-laminates have laminated structures sub-micrometer thick composed of Mg and Cu layers with dense lattice defects. The super-laminates after initial activation keep laminated structure and have uniformly distributed pores sub-micrometer in diameter. It is considered that these micro/nano-structures of Mg/Cu super-laminates lead to lower dehydrogenation temperature and better kinetics.
A Study of GDC-Based Micro Tubular SOFC
Authors: Sammes Nigel , Song J. , Roy B. , Galloway K. , Suzuki Toshio , Awano Masa , Serincan A.M. Fazil
Published: January 2010

In this work, we studied a NiO/GDC-GDC-LSCF micro-tubular SOFC system using saturated hydrogen at 450-550 oC. The systems were electrochemically and mechanically tested using a number of different methodologies, and were modeled using a 2D axial symmetric steady state non-isothermal computational model incorporating radiation heat transfer, flow and species transport.
The Use of Bobbin Tools for Friction Stir Welding of Aluminium Alloys
Authors: Threadgill Philip L. , Ahmed M.M.Z. , Martin Jonathan P. , Perrett Jonathan G. , Wynne Bradley P.
Published: January 2010

The use of a double sided friction stir welding tool (known as a bobbin tool) has the advantage of giving a processed zone in the workpiece which is more or less rectangular in cross section, as opposed the triangular zone which is more typically found when conventional friction stir welding tool designs are used. In addition, the net axial force on the workpiece is almost zero, which has significant beneficial implications in machine design and cost. However, the response of these tools in generating fine microstructures in the nugget area has not been established. The paper presents detailed metallographic analyses of microstructures produced in 25mm AA6082-T6 aluminium wrought alloy, and examines grain size, texture and mechanical properties as a function of processing parameters and tool design, and offers comparison with data from welds made with conventional tools.
Toughness of Advanced High Strength Bainitic Steels
Authors: Caballero Francisca G. , Chao J. , Cornide J. , Garcia-Mateo Carlos , Santofimia Maria Jesus , Capdevila Carlos
Published: January 2010

Carbide free bainite has achieved the highest strength and toughness combinations to date for bainitic steels in as-rolled conditions. By alloying designing and with the help of phase transformation theory, it was possible to improve simultaneously the strength and toughness because of the ultra-fine grain size of the bainitic ferrite plates. Ultimate tensile strengths ranging from 1600 MPa to 1800 MPa were achieved while keeping a total elongation higher than 10 %. Their toughness at room temperature matches tempered martensitic steels, known to be the best-in-class regarding this property. However, it has been observed that the presence of coalesced bainite leads to a dramatic deterioration in toughness in these novel high strength bainitic steels.
Study of the Key Issues of Friction Stir Welding of Titanium Alloy
Authors: Liu Hui Jie , Zhou Li , Huang Yong Xian , Liu Qi Wei
Published: January 2010

As a new solid-state welding process, friction stir welding (FSW) has been successfully used for joining low melting point materials such as aluminum and magnesium alloys, but the FSW of high melting point materials such as steels and titanium alloys is still difficult to carry out because of their strict requirements for the FSW tool. Especially for the FSW of titanium alloys, some key technological issues need to solve further. In order to accomplish the FSW of titanium alloys, a specially designed tool system was made. The system was composed of W-Re pin tool, liquid cooling holder and shielding gas shroud. Prior to FSW, the Ti-6Al-4V alloy plates were thermo-hydrogen processed to reduce the deformation resistance and tool wear during the FSW. Based on this, the thermo-hydrogen processed Ti-6Al-4V alloy with different hydrogen content was friction stir welded, and the microstructural characterizations and mechanical properties of the joints were studied. Experimental results showed that the designed tool system can fulfill the requirements of the FSW of titanium alloys, and excellent weld formation and high-strength joint have been obtained from the titanium alloy plates.
Prediction and Measurements of Thermal Residual Stresses in AA2024-T3 Friction Stir Welds as a Function of Welding Parameters
Authors: Dubourg Laurent , Doran P. , Gharghouri Michael A. , Larose Simon , Jahazi Mohammad
Published: January 2010

Friction Stir Welding (FSW) induces thermal residual stresses resulting in distortions in thin-walled structures. In order to understand and quantify this phenomenon, simulations and experiments of FSW on aluminium alloy (AA) 2024-T3 have been performed using different rotational and welding speeds. A sequentially coupled finite element (FE) model was used to study the residual stresses caused by the thermal cycling induced from FSW. The 3D FE model used temperature-dependent mechanical and thermophysical material properties. The predicted longitudinal stresses peaked at ~300 MPa and had a ‘‘W’’ profile with tensile stress peaks in the weld and compressive stresses outside the weld. In the FE model, the influence of process parameters on residual stress distribution was studied. The application of ‘hot’ welding conditions, i.e. low welding speed and high rotational speed, increased the residual stresses significantly, mainly in the transverse direction. Conversely, ‘cold’ welding conditions resulted in lower residual stresses. The magnitude and distribution of the residual stresses predicted by the FE model were validated by neutron diffraction. The results indicate a good agreement between the measured and predicted residual stresses in AA2024-T3.
Mechanical and Microstructural Characterisation of Dissimilar Friction Stir Welded AA2024-T3 and AA7075-T6 Aluminium Alloys
Authors: da Silva A.A.M. , Aldanondo E. , Alvarez P. , Lizarralde A. , Echeverria A.
Published: January 2010

Friction Stir Welding (FSW) is a solid-state joining process whereby no bulk melting of the base material occurs during joining. FSW avoids severe distortion and formation of as-cast coarse microstructure as well as defects arising from melting and solidification during traditional fusion welding processes. The objective of this investigation is to evaluate the effect of joining parameters on the mechanical and microstructural properties of dissimilar aluminium alloys (3 mm thick AA2024-T3 and AA7075-T6 sheets) joints produced by FSW. Microstructural features have been analysed; while mechanical performance has been investigated in terms of hardness and tensile testing. In both welding configurations the boundary between the base materials at the stir zone is clearly delineated, i.e., no material mixing is observed.
Novel Approaches to Friction Spot Welding Thin Aluminium Automotive Sheet
Authors: Prangnell Phil B. , Bakavos Dimitrios
Published: January 2010

Conventional welding methods, like resistance spot welding, are inefficient and difficult to apply to light alloys. Two alternative new solid state friction joining techniques, which have not yet been fully optimized, are high power Ultrasonic Spot and Friction Stir Spot Welding (USW & FSSW). Here we have compared the performance for these two processes for producing ‘keyhole-less’ welds in thin aluminium automotive closure panels. For friction stir spot welding this was achieved through using a novel ‘pinless’ tool to create a joint without a retained keyhole and reduce the weld cycle time. The properties of the welds that can be produced by each technique are compared, together with the stages of weld formation, and the relationship between welding conditions and joint performance.
The Alloy Design and Thermomechanically Controlled Processing (TMCP) of Plate for High Pressure, Large Diameter Pipelines
Authors: Garcia C. Isaac , Cho K. , Hua Ming Jian , DeArdo Anthony J.
Published: January 2010

Modern, cost-effective pipelines are moving beyond the API X70-X80 limits of the 1990s. Over the last few years, more interest has been placed on the X100-120 grades because they are potentially more economical to build and operate. To reach the impressive properties required by these new grades, the proper combination of alloy and rolling process design must be implemented, along with highly controlled interrupted accelerated cooling and hot leveling. This paper discusses some of the underlying physical metallurgy that is required and points out areas where further research and development would be useful.
Formability of Friction Stir Welded AZ31 Magnesium Alloy Sheets
Authors: Forcellese Archimede , Fratini Livan , Gabrielli Filippo , Simoncini M.
Published: January 2010

The formability of friction stir welded AZ31 magnesium alloy sheets was investigated by means of uniaxial tensile and hemispherical punch tests performed under different process conditions. The results of the tensile tests were analysed in terms of flow stress and ductility at different temperature and strain rate; the hemispherical punch tests, carried out at different temperatures, provided the limiting dome height. The formability of FSW-ed blanks was compared to the one exhibited by the base material in order to evaluate the quality of the welded joints.
Effects of Tool Design and Friction Stir Welding Parameters on Weld Morphology in Aluminum Alloys
Authors: Widener Christian A. , Burford Dwight A. , Jurak Sarah
Published: January 2010

Friction stir welding (FSW) is a complex thermo-mechanical process which produces wrought microstructure with microstructural gradients in grain size, grain orientation, dislocation density, and precipitate distribution. The type and degree of microstructural modification is a function of the particular alloy chosen, its initial temper, the tool design and corresponding weld process parameter window, and other variables like material thickness, size, fixturing, etc. Since the microstructural changes produced can dramatically affect resultant mechanical performance and corrosion response, a thorough understanding of the variables involved in those changes is needed. A design of experiments approach was used to study the effects of welding parameter selection on the microstructural changes wrought by FSW with two different sizes of the same FSW tool design. A combination of microhardness mapping and electrical conductivity testing was used to investigate potential differences. The importance of these factors and the means for characterizing them for developing standards and specifications are also discussed.
Development of Local Reinforcement and Local Metallic Foam Using FSP
Authors: Yamamura Koshi , Nishihara Tadashi
Published: January 2010

Friction stir welding (FSW) has been generating interest in association with friction stir processing (FSP), a new technique that employs FSW tooling. In a recent study, this author investigated the excellent fluidity of aluminum alloy with FSP for creating metal matrix composites (MMCs) by the local dispersion of aluminum oxide particulate in aluminum alloy. In this study, two novel methods of property modifications, local reinforcement and local metallic foam of 6061 aluminum alloy by FSP, are proposed. Tungsten carbide (WC) particulate and SiC whisker reinforced aluminum alloy plate are produced for local reinforcement of 6061Al by FSP. FSP can also produce local aluminum composites containing titanium hydride (TiH2) particles. These results, which indicate the feasibility of producing local metallic foam by FSP, are discussed in terms of microstructure and mechanical properties.
Fabrication and Processing of Gamma Titanium Aluminides - A Review
Authors: Chen Yu Yong , Chen Yan Fei , Kong Fan Tao , Xiao Shu Long
Published: January 2010

The paper outlines some research work that has been conducted in Harbin Institute of Technology, on the fabrication of TiAl alloys. The review is presented with special emphasis on some different manufacturing routes of TiAl alloys, including investment casting, canned forging and sheet rolling, mechanical milling and rapid solidification. Investment casting has been developed to manufacture near-net shape TiAl blades. Also included are current development of canned forging and rolling for TiAl sheets. Then, TiAl nanocrystalline powders gained through low temperature and two steps mechanical milling were researched. And considerably refined TiAl alloys with Y additions were produced by rapid solidification and the microstructure evolution with Y addition was studied. Details of the processing route and microstructure related to different processing method will be presented.
Low Cycle Fatigue and Cyclic Deformation of TiAl Alloys
Authors: Hénaff Gilbert , Berteaux Olivier , Jouiad Mustapha , Thomas Marc
Published: January 2010

The relation between microstructural parameters, microscopic cyclic deformation mechanisms and macroscopic cyclic strain hardening is investigated in the case of a heat treated PM Ti-48Al-2Cr-2Nb alloy at 20°C and at 500°C. In particular it is shown that, for the different microstructures considered, a moderate hardening is related to the formation of highly tangled dislocation structures which is in turn controlled by the dislocation glide mean free path. At 500°C this structures evolves towards a braid like structure for the fine fully lamellar microstructure.
Physical and Mechanical Properties of Single Crystals of Co-Al-W Based Alloys with L12 Single-Phase and L12/fcc Two-Phase Microstructures
Authors: Inui Haruyuki , Oohashi Takashi , Okamoto Norihiko L. , Kishida Kyosuke , Tanaka Katsushi
Published: January 2010

The values of all the three independent single-crystal elastic constants and polycrystalline elastic constants of Co3(Al,W) experimentally determined by resonance ultrasound spectroscopy at liquid helium temperature are 15~25% larger than those of Ni3(Al,Ta) but are considerably smaller than those previously calculated. Because of the large value of E111/E100 and cij of Co3(Al,W), two-phase microstructures with cuboidal L12 precipitates well aligned parallel to <100> and well faceted parallel to {100} are expected to form very easily in Co-base alloys, as confirmed indeed by experiment. Values of yield stress obtained for [001]-oriented L12/fcc two-phase single crystals moderately decrease with the increase in temperature up to 800°C and then decrease rapidly with temperature above 800°C without any anomaly in yield stress.
Various Properties of Dual-Phase Intermetallic Compound in Ni-Al System
Authors: Iwabuchi Yoshitaka , Kobayashi Isao
Published: January 2010

NiAl possesses the superior oxidation resistant and Ni3Al shows the good high temperature strength. Various castings with NiAl and Ni3Al were used in order to investigate the influence of Ni content on the properties. The heats were made by using vacuum induction furnace and its properties were evaluated. This article described the density, hardness, oxidation resistance, corrosion resistance and compression strength of the castings in comparison of other structural materials.
Forging of Titaniumaluminide Parts
Authors: Janschek Peter
Published: January 2010

A new material is available that displays the high temperature mechanical properties of nickel alloys at half the density –the intermetallic Titaniumaluminides. These extraordinary properties give it great potential for lightweight construction in aeroengines. The high Young’s modulus compared to common Titanium alloys offers advantages even in light weight applications, which do not need high heat resistance, e. g. connection rods. However, its characteristic rather like ceramics than metals presents a challenge in terms of forming. A forging technology has been developed with respect to this behaviour. Using isothermal forging at high temperatures with extremely low strain rates allows a material related forming. High pressure compressor blades and low pressure turbine blades have been forged as well as con rod for sports car engines. For economical improvement several blades may be forged at the same time.
New Trends in Advanced High Strength Steel Developments for Automotive Application
Authors: Kwon Ohjoon , Lee Kyoo Young , Kim Gyo Sung , Chin Kwang Geun
Published: January 2010

The body design with light weight and enhanced safety is a key issue in the car industry. Corresponding to this trend, POSCO is developing various automotive steel products with advanced performance. Conventional advanced high strength steels such as DP and TRIP steels are now expanding their application since the steels exhibit higher strength and ductility than those of conventional solution and precipitation strengthened high strength steels. Efforts have been made to enhance the mechanical performance of these steels such as ductility, hole expansion ratio, deep drawability, etc. Current research is focused on development of extra- and ultra-AHSS. Extra-AHSS are designed to utilize nano-scale retained austenite embedded in fine bainite and martensite. Ultra-AHSS are designed to have austenite as the major phase, and the ductility is enhanced primarily by continuous strain hardening generated during forming. These steels including extra- and ultra-AHSS are believed to be the next generation automotive steels which will replace the existing high strength steels due to their extremely high strength and ductility combinations.
Second Phase Precipitation within a Laves Phase in the Ir-Y Binary System
Authors: Sekido Nobuaki , Yamabe-Mitarai Yoko
Published: January 2010

A Laves phase Ir2Y is found to exhibit a temperature dependent solubility, which yields
Ir3Y precipitation within the Ir2Y matrix of an arc-melted Ir-30at.%Y alloy. Microstructure
observations have confirmed that the precipitation of Ir3Y has already started in the as-cast state.
Upon annealing of an as-cast Ir-30at.%Y, the volume fraction of Ir3Y precipitates increases and
finally reaches about 50%. The orientation relationship between Ir3Y and Ir2Y has been identified
as: (0001)Ir3Y//(111)Ir2Y and [21
_
1 _
0]Ir3Y//[1
_
10]Ir2Y. The orientation relationship is rationalized by
the atom matching at the habit plane between the two phases.
The Effects of Heat Treatments and Tungsten Additions on Microstructures and Tensile Properties of Powder Metallurgy Ti-48Al-2Nb-2Cr
Authors: Seo Dongyi , Bulmer S. , Saari H. , Au Peter
Published: January 2010

The microstructures and tensile properties of a fully lamellar Ti-48Al-2Cr-2Nb, and two tungsten-modified versions, Ti-48Al-2Cr-2Nb-0.5W and Ti-48Al-2Cr-2Nb-1.0W (atomic percent) are investigated. Gas atomized powders are consolidated by hot isostatic pressing followed by solution treatment and aging. The microstructures are characterized by optical, scanning electron, and transmission electron microscopy and mechanical properties are characterized by room temperature tensile testing. The solution heat treatment, combined with controlled cooling, generates relatively fine, fully lamellar grains. Tungsten reduces the propensity for martensitic gamma formation during cooling, and slows down lamellar coarsening as well as the formation of equiaxed gamma phase during aging. The aging treatment stabilizes the microstructure and, in the tungsten-modified alloys, causes beta phase precipitation at lamellar interfaces and grain boundaries. Both aging and tungsten additions increase the alloy strength and reduce ductility. The fracture morphologies of the alloys are similar and exhibit mixed-mode fracture consisting of inter- and intra-granular cracking, as well as inter-lamellar cracking.
Surface Modification to Enhance Fatigue Performance of Steel: Applications of Deep Rolling
Authors: Matlock David K. , Richards Mark D. , Speer John G.
Published: January 2010

With the development of new steels and processing techniques, there have been corresponding advances in the fatigue performance of steels. Methods to increase fatigue performance are typically designed to produce gradients in surface properties and are based on heat treating operations, including enhanced carburizing and induction hardening, as well as surface mechanical deformation. In this paper selected examples based on recent work on deep rolling is used to illustrate the importance of the base steel properties on the final performance of surface modified materials. The degree of fatigue improvement by deep rolling, a process to mechanically deform fillet surfaces to improve fatigue resistance in cylindrical components, depends on the deformation response of the substrate to the rolling process. Recent results on the behavior of three medium carbon steel alloys deformed at temperatures up to 360 °C, are discussed. Deep rolling increased fatigue resistance, and the degree of improvement was higher when deep rolling was applied in the dynamic strain aging (DSA) temperature range rather than at room temperature. Observed variations in fatigue performance are interpreted based on fundamental deformation mechanisms and are used to present an overall perspective on approaches to increase the fatigue resistance of conventional and newly developed steels.
Effect of Trace Boron Addition on the Microstructure and Tensile Elongation of Ti2AlNb-Based Orthorhombic Titanium Alloys
Authors: Hagiwara Masuo , Kitaura Tomoyuki
Published: January 2010

The grain sizes of two kinds of orthorhombic alloys, namely (O+B2) Ti-22Al-11Nb-2Mo -1Fe and (O+2) Ti-27.5Al-13Nb have been successfully reduced by the addition of trace boron (B) (less than 0.12 wt.%). For example, the grain size in the B2 solution-treated condition was reduced from 1 mm to 80 m by the addition of 0.05% B for both alloys. The tensile elongation of Ti-22Al-11Nb-2Mo-1Fe at room temperature and 650C was increased from 0.3% to 4.3%, and from 8.2% to 30.3%, respectively, by the addition of 0.10% B. Ti-27.5Al-13Nb also showed an improved room temperature ductility by the minor B addition.
DSC and Microstructural Investigations of the Elektron 21 Magnesium Alloy
Authors: Kiełbus Andrzej , Rzychoń Tomasz , Przeliorz Roman
Published: January 2010

The paper presents the results of DSC and microstructural investigations of Elektron 21 magnesium alloy in as cast condition and after solution hardening. Elektron 21 is a magnesium based casting alloy containing neodymium and gadolinium for used to at 200°C in aerospace application. The solution heat treatment was performed at 520°C/8h/water. Ageing treatment was performed at different temperatures 200, 250, 300 and 350°C, then quenched in air. The microstructure of Elektron 21 in as cast condition consists of primary solid solution α -Mg grains with eutectic α-Mg + Mg3(Nd,Gd) phase and regular precipitates of MgGd3 phase. After DSC investigations three exothermal signals has been observed. First exothermal signal at ~170÷245°C assigned to an undifferentiated formation of the metastable phases β” and β’ and the second one at ~280°C corresponded to the formation of a stable β (Mg3Nd) phase. The last signal at ~300°C was connected to the formation of Mg41Nd5 phase. Regular precipitates of MgGd3 phase have been also observed. TEM investigation confirmed that the Elektron 21 alloy precipitate from the solid solution according to the sequence of the following phases: α–Mgβ”β’β(Mg3Nd)Mg41Nd5
Corrosion Protection and Microstructure of Magnesium Alloys Anodized by Phosphate Solution
Authors: Murakami Koji , Hino Makoto , Saijo Atsushi , Kanadani Teruto
Published: January 2010

Corrosion protection by anodization and conversion treatment in phosphate solution was studied by microstructural and electrochemical analysis. Both the anodized and the conversion-treated layers showed sacrificial protection in a solution of sodium chloride. The corrosion current or the dissolving rate of the anodized layer was smaller than that of the conversion-treated surface. The modified layers had another mode of protection to form protective films on magnesium substrate where the original modified layers were mechanically lost. Since the state of magnesium in the anodized layer is close to magnesium oxide, phosphorus in the layer is considered to have an important role in these properties concerning the above corrosion protection.
Effect of Manufacturing Process on the Final Properties of Advanced High Strength Steels for Automotive Applications
Authors: Pereloma Elena V. , Timokhina Ilana B. , Hilditch Tim B. , Hodgson Peter
Published: January 2010

The performance of multiphase steels with high strength and improved toughness or ductility, such as intercritically annealed dual-phase (DP) and transformation-induced plasticity (TRIP) steels, is of key importance to the automotive industry. In this work we have considered the entire manufacturing process and the effects of this on the final product performance. These steels are formed to produce the required final shape and then the car is paint baked. In this work we also consider the effect of cold working and bake hardening on the fatigue life of the components.
High Temperature Deformation of Wrought Zn-Containing Magnesium Alloys
Authors: Spigarelli Stefano , El Mehtedi Mohamad , Ciccarelli D. , Bamberger Menachem , Cupitò Giuseppe , Rami Y.
Published: January 2010

The high temperature response in torsion and creep of two extruded Mg-Zn alloys was investigated in the present study. The alloy 0 (Mg-2Zn-1Mn) was found to exhibit a lower strength than the alloy 2 (Mg-0.55Zn-0.79Mn-0.75Al-0.17Ca), even if the activation energy for creep was similar for both materials (170-180 kJ/mol). The difference in flow stress was here preliminarily attributed to the precipitation of fine Al2Ca particles.
Improvement of Magnesium Sheet Formability by Alloying Addition of Rare Earth Elements
Authors: Yi Sang Bong , Letzig Dietmar , Hantzsche Kerstin , Gonzalez Martinez Rodolfo , Bohlen Jan , Schestakow Igor , Zaefferer Stefan
Published: January 2010

The influences of rare earth elements addition on the crystallographic texture and microstructural evolutions are examined during rolling and annealing of Mg-sheets. In case of Nd or Y additions, dynamic recrystallisation is suppressed such that the deformed microstructure is observed after hot rolling with relatively large strain per pass. Cold rolled binary Mg-Nd alloy sheet shows strong texture with splitting of the basal poles in the rolling direction, however, the texture intensity decreases significantly during the recrystallisation annealing. From the comparison of deep drawing behaviours between commercial ZE10 and AZ31 sheets, it is observed that the addition of the rare earth elements and accompanying texture changes result in the improved formability.
DC Casting - Simulation and Microstructure of Mg-Zn Alloys
Authors: Harel Galia , Bamberger Menachem , Rami Y. , Spigarelli Stefano , El Mehtedi Mohamad , Cupitò Giuseppe
Published: January 2010

The market share of wrought Magnesium products such as structural and functional components is recently increasing. Extrusion at elevated temperatures is used to produce reliable plastic deformation, since magnesium alloys have limited ductility at room temperature. In order to produce sound extruded products, high quality billets are required. Understanding the influence of direct chill casting conditions on the production properties such as quality, safety, workability and microstructure have a profound importance. Comprehensive computer simulations were used in order to model the casting so that process parameters can be identified and controlled, resulting in significant benefits. The aim of modeling is to provide temperature profiles for a more accurate solidification analysis, predict the solidification time and the effect of cooling on the solidification. The experimental study included castings of several Magnesium alloys, each with 7 (seven) thermocouples that were submerged into the billet. Verification of the simulations was carried out based on the data collected. Complimentary work was conducted on microstructure analysis in as cast and as-extruded states.
Microstructure and Creep Properties of AJ62 and AE44 Die-Casting Magnesium Alloys
Authors: Kiełbus Andrzej , Rzychoń Tomasz
Published: January 2010

Microstructure and tensile creep behaviour of the die-cast AE44 and AJ62 magnesium alloys has been studied at temperatures between 175°C and 200°C and at stresses in the range from 60 to 75 MPa. At the 175°C the AJ62 and AE44 alloys exhibit good creep resistance after 120h creep deformation. At 200°C the AE44 alloy shows still good creep resistance, whereas in the case of AJ62 alloy the rapid decreasing of creep resistance has been observed. TEM observations reveal dislocations cell structure in AE44 alloy after creep test. In AJ62 alloy subgrain formation and decreasing the dislocation density have been observed.
Formability of AZ31 Alloys Prepared by Hot-Extrusion of their Machined Chips
Authors: Matsuzaki Kunio , Murakoshi Yoichi , Shimizu Toru , Kikuchi Kaoru
Published: January 2010

Machined AZ31 alloy chips were consolidated by hot-pressing and then hot-extrusion at 300 °C, and their workability was evaluated. The consolidated sample has a fully dense microstructure with fine equiaxed grains. The　compression and backward extrusion tests reveal that the consolidated AZ31 chips have a good workability at above 200°C.　It is said that the recycled AZ31 alloy by hot-extrusion of the chips is suitable for forging materials and the process is useful for the recycling of Mg chips.
Atomic Scale Simulation of Deformation in Magnesium Single Crystals
Authors: Phelan Dominic , Stanford Nicole , Thijsse B. , Sietsma Jilt
Published: January 2010

The deformation behaviour of magnesium single crystals under plane strain conditions has been examined using molecular dynamics modelling. The simulations were based on an existing atomic potential for magnesium taken from the literature. A strain of 10% was applied at rates of 3x109s-1 and 3x107s-1. The simulations predicted the formation of mechanical twins that accommodated extension in the c-axis direction of the hexagonal unit cell. However, the predicted twin is not of the same kind found in magnesium, but is that commonly observed in titanium. It is believed that further analysis of the physical properties predicted by this interatomic potential will shed more light on the atomic processes controlling twinning in Magnesium alloys. It also highlights the need for improvements to the interatomic potential such that more accurate deformation behaviour can be attained.
Formation of Fold Defects in Permanent Mold Cast AE42 Magnesium Alloy
Authors: Bichler Lukas , Ravindran Comondore
Published: January 2010

Application of magnesium alloys potentially plays a key role in weight reduction of automotive and aerospace components. Majority of magnesium components are manufactured via the high-pressure die-casting (HPDC) or permanent-mold casting (PMC) processes. In general, castability of magnesium alloys is comparable to aluminum alloys. However, unique defects related to the high susceptibility of magnesium to rapidly solidify, dissolve hydrogen or form oxides potentially contribute to material failure.
In this research, AE42 magnesium alloy castings were manufactured via the PMC process. Formation of fold defects in regions of high melt turbulence was observed on the macro-scale as visible surface flow-lines. Microstructural analysis revealed that folds in the AE42 alloy we related to the rapid solidification and short alloy freezing range. Further, segregation of Al2RE intermetallics at the metal front hindered proper fusion of merging metal fronts.
Creep Behavior of Two Series Magnesium Alloys
Authors: Sun Yang Shan , Bai Jing , Xue Feng
Published: January 2010

The creep behavior of two series of magnesium alloys, Mg-4Al based alloys with strontium addition and binary Mg-Nd alloys, has been studied. Results show that the high creep properties achieved by the Mg-Nd alloys are attributed to the precipitation of tiny dispersed β’ particles, which form and effectively restrict the dislocation slipping and climb during creep deformation. In terms of values of the stress exponent and apparent activation energy gained from systematic creep tests, the mechanism responsible for creep deformation of the Mg-Nd alloys is inferred as dislocation climb, which is supported by TEM observations performed on the Mg-2Nd alloy after creep test. For the Mg-4Al based alloys, however, microstructural observations reveal that the significant improvement on creep properties caused by Sr addition is accounted for the formation of an interphase network consisting of Al4Sr and a Mg-Al-Sr ternary compound distributing at grain boundaries. The breakage of the interphase network after extrusion results in a sharp drop of creep properties, indicating the creep deformation of the alloy is controlled mainly by grain boundary sliding, which is in contradiction to the mechanism for creep of the alloys inferred by the classical criterions based on the values of stress exponent and apparent activation energy.
Rotary-Die Equal Channel Angular Pressing Method for Light Metals
Authors: Watazu Akira , Shigematsu Ichinori , Hakamada Masataka , Suzuki Kazutaka , Huang Xin Sheng , Saito Naobumi
Published: January 2010

A new ECAP process method called rotary-die ECAP (RD-ECAP) was developed to form fine-grained bulk materials such as aluminium alloys, magnesium alloys, aluminium composites, and titanium, all of which can be processed under conditions of 573-773K, at an approximately 0.9-2.4 mm/s punch speed of 300MPa or lower. By the RD-ECAP method, ECAP processing of up to 2 passes can be done without sample removal and samples processed over 30 cycles were obtained.
Characterization of FePt Nanopowder Synthesized by a Chemical Vapor Condensation (CVC) Process
Authors: Jang Tae Suk , Yu J.H. , Lee D.W. , Kim B.K.
Published: January 2010

FePt binary alloy nanopowder has been synthesized by a chemical vapor condensation process using a mixture of iron acetylacetonate and platinum acetylacetonate. Particle size of the synthesized powder was less than 10 nm and the powder had very narrow size distribution with relatively high dispersivity. FePt nanopowder possessing L10 ordered phase was synthesized at the condition of well controlled precursor mixing ratio and reaction temperature with some disordered cubic phase.