bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimising Thermomechanical Processing with Reduced Energy Demand
Authors: Siwecki Tadeusz , Eliasson Johan
Published: January 2012

Improving the steel properties and production processes with reduced energy demand for high strength steels requires improved process control in close relation to the steel composition. Hot rolling of steel is an energy-intensive process, especially in respect of preheating the steel slabs. The present work was carried out with the aim of reducing the initial slab temperature while at the same time improving properties by optimization of the steel composition and process parameters. Optimization of slab reheating and hot rolling parameters in connection with plate and strip rolling was carried out on low C-Mn high-strength steels microalloyed with Mo-Ti-Nb-B, both in laboratory and full scales processing. The effects of a low slab reheating temperature, high finish rolling temperature (FRT) during thermo-mechanical controlled processing (TMCP) and accelerated cooling rates following hot rolling to RT or to the coiling temperature have been investigated. Improvement of yield strength of the plate has been obtained by lowering the slab reheating temperature, especially with high cooling rates (>20°C/s) to room temperature. The results obtained for strip steels also show that a reduced reheating temperature combined with high finish rolling temperatures and cooling rates (>20°C/s) to a coiling temperature of 450°C produces very positive microstructures and mechanical properties in the present steels. Lowering the slab reheat temperature reduces energy consumption and accordingly releases less CO2 into the atmosphere during the thermo-mechanical processing of the present steels.
Microstructure and Property Characteristics of CSP®-Produced Advanced High Strength Steels
Authors: Sun Wei Ping
Published: January 2012

The recent major achievements obtained during the development of advanced high strength steels (AHSS) at Nucor Corporation are briefly described in this article. Due to the innovative chemistry designs as well as strictly controlled thermomechanical schedules at CSP® and down-stream processing, these newly developed AHSS products possess fine, uniform microstructure, and exhibit higher strength-elongation balance, better formability and stretch flangeability, improved impact toughness and crashworthiness, as well as superior weldability and weld fatigue properties. Moreover, the property consistency of these innovative AHSS has been markedly improved.
Physical and Mathematical Modeling of Austenite Microstructure Evolution Processes Developing in Line-Pipe Steels under Hot Rolling
Authors: Vasilyev Alexander A. , Rudskoi Andrey , Kolbasnikov N.G. , Sokolov Semen , Sokolov Dmitry F.
Published: January 2012

An experimental study (physical modeling) of the processes of austenite microstructure evolution occurring under hot rolling was performed for line-pipe steels with different chemical composition. All investigations were conducted with the help of the Gleeble 3800 system. Empirical quantitative models of austenite grain growth, static and dynamic recrystallization, as well as a flow stress model were developed. The effect of complex alloying by such elements as C; Mn; Si; Ni; Mo; Nb; Ti; and V on grain growth and recrystallization is accounted for under the condition that all elements are in a solid solution. The set of the models empirical parameters is determined utilizing corresponding experimental data available from literature. Modeling results for static recrystallization and flow stress in the investigated steels are compared with experimental data.
New Development and Application of Microalloyed Medium Carbon Steel for Auto Forging Products
Authors: Zhang Ying Jian , Dong Han , Hui Wei Jun , Peng Jun
Published: January 2012

Microalloyed medium carbon steels have been applied for auto forging products at the aim of lower cost since 1980’s in China. Without quenching and tempering processes, the cost of heat treatment was greatly decreased, so they are widely applied in car forgings such as crankshaft, connecting rod. Recently, with the aim of improving performance and reducing production cost, new technologies, such as: reductions of microalloyed elements, tailored components, and mechanical properties forecast, have been developed in China auto industry. The designation, processing, properties prediction and microstructure of auto components have been controlled comprehensively. With the development of new technologies, microalloyed medium carbon steel gradually began to be applied to product important parts, and replace Quenching and Tempering steels. Both steel makers and end product users are expressed their desire to share benefits of technological innovation. The technologies will have a huge developing space and very bright developing prospects in motor parts industry in future.
Transformation of a High Strength Steel during Deformation at α/γTemperature
Authors: Wang J.T. , Zhang Ai Wen , He X.M. , Jiao Si Hai
Published: January 2012

The relatively higher alloy content of AHSS leads to complex transformation behavior after finishing rolling and the transformation is unable to complete just after coiling, which causes some extent of deformation due to the transformation dilation. In the present study, low strain rate deformation was performed at γ/α temperature zone after the sample was deformed to simulate the deformation and transformation interaction after coiling by using Gleeble 3800 thermo-mechanical simulator. All the flow stress curves display a sharp decrease after certain strain when deformation temperatures below 750°C. The interaction between deformation and transformation is used to explain the phenomena.
Texture Effects in Solid-State Reactions of Thin Films
Authors: De Keyser Koen , Detavernier Christophe , Sweet Jean Jordan , Lavoie Christian
Published: January 2012

The texture of thin films, originating from a solid state reaction between a deposited film and a single crystal substrate is investigated. The relation between the phase formation and texture is analyzed for a number of these systems, such as Co/Si, Ni/Si or Co/Ge, where a metal film is allowed to react with a semiconductor single crystal substrate during heating and a summary of these results in presented in this article. It was found that the texture of the resulting films can be very complex, consisting of a variety of simultaneously occurring texture components such as epitaxy, fiber and axiotaxy texture. The close connection between the phase formation and texture is demonstrated by the fact that even a small intervention in either one, can have a huge effect on the resulting phase and/or its texture. From this, we show that the effect of the addition of ternary elements (e.g. Pt, W, C) to the thin films can only be understood if one considers its effects on both the kinetics and the thermodynamics of the reactions, as well as on the texture of the phases. We show how this can be used to influence technologically important properties of the films, such of formation temperature or stability.
A Simple Method to Create Superhydrophobic Aluminium Surfaces
Authors: Jafari R. , Farzaneh Masoud
Published: January 2012

Superhydrophobic surfaces were prepared using a very simple and low-cost method by spray coating. A high static water contact angle of about 154° was obtained by deposition of stearic acid on an aluminium alloy. However, this coating demonstrated a high contact angle hysteresis (~ 30º). On the other hand, superhydrophobic surfaces with a static contact angle of about 162º and 158º, and a low contact angle hysteresis of about 3º and 5º were respectively obtained by incorporating nanoparticles of SiO2 and CaCO3 in stearic acid. The excellent resulting hydrophobicity is attributed to the synergistic effects of micro/nanoroughness and low surface energy. A study of the wettability of these surfaces at temperatures ranging from 20 to-10 °C showed that the superhydrophobic surface becomes rather hydrophobic at supercooled temperatures.
Observation of Stress-Driven Migration of Specific Planar Grain Boundaries in Al Bicrystals
Authors: Molodov Dmitri A. , Gorkaya Tatiana , Gottstein Günter
Published: January 2012

Stress induced grain boundary migration was experimentally investigated in aluminum bicrystals. Migration of planar symmetrical <100> and <111> tilt boundaries under a shear stress was observed to be accompanied by a lateral translation of the adjacent grains. This coupling proved to be the typical migration mode for all investigated boundaries, no matter whether low-or high angle, low Σ CSL coincidence or non-coincidence boundary. The migration-shear coupling was also observed for asymmetrical tilt boundaries. Measurements of the temperature dependence of coupled boundary migration revealed that there is a specific misorientation dependence of the migration activation parameters. Contrary to expectations, a high angle Σ7 tilt boundary moved under an applied stress, but produced practically no shear during its migration.
Plastic Domain Microstructure and Hardness Analysis of Indented Layered Composite
Authors: Muraishi Shinji , Takaya Masaaki
Published: January 2012

The size dependent hardening in Al-4wt%Cu thin film on Si substrate has been investigated by the numerical calculation of indentation stress field and the observation of plastic zone microstructure of indented film. Distribution of internal stress predicted by triangular dislocation loop (TDL) model shows no size dependency with the different number of dislocations when the constant line density is assumed at the contact surface. TEM cross-sectional observation reveals that the plastic deformation is dominantly induced inside the film, and the growth of plastic zone is restricted at the interface of hard Si substrate. The size dependent hardening in soft film and hard substrate system is discussed from the change in dislocation density with respect to the plastic zone microstructure.
Microstructure Coating Influence for Optimized Diamond Deposition
Authors: Poulon-Quintin Angéline , Faure Cyril , Teulé-Gay Lionel , Manaud Jean Pierre
Published: January 2012

Diamond films grown by Chemical Vapor Deposition (CVD) are widely used as surface overlay coating onto WC-Co cutting tools to develop their performances. To improve the diamond adhesion with the substrate, many pre-treatment methods have been applied such as giving a suitable diffusion barrier layer on the substrates. Single zirconium and tantalum nitride layers have been sputtered onto WC-Co substrates as diffusion barriers and buffer layers under specific reactive sputtering conditions. Microstructure of the tantalum nitride layer has been controlled using process parameters in order to understand mechanisms occurring during Co diffusion in correlation with microstructure. Moreover, a multilayer coating composed of TaN and ZrN thin film sequences as diffusion barrier is also evaluated. To improve the nuclei density of diamond during CVD processing, a thin Mo extra layer has been added (500 nm) whatever the diffusion barrier used. In this study, bilayer and multilayer systems have been tested to optimize nanocrystalline CVD diamond deposition grown with negative biased substrates. For all systems, after diamond deposition, a massive carburization of molybdenum and tantalum nitride is observable whereas zirconium nitride is not. A TEM study is done to improve understanding of phenomena occurring at the interfaces during the process. The key role played by each layer microstructure is discussed.
Diffusion Behavior and Interfacial Reaction of Heterogeneous Metal Systems Controlled by High Magnetic Fields
Authors: Li Dong Gang , Wang Qiang , Wang Kai , Wu Chun , Li Guo Jian , He Ji Cheng
Published: January 2012

The interdiffusion behaviors and interfacial reaction in solid Cu/solid Ni, liquid Bi/solid Bi0.4Sb0.6, liquid Al/solid Cu, and gas Al/solid Cu diffusion couples have been experimentally studied under a high magnetic field of up to 12T. The effects of magnetic flux density and the direction of magnetic field (B) on the evolution of interfacial microstructure (including interfacial migration, phase composition and thickness of diffusion layers) have been examined systematically. We found that (1) The shift distance of Kirkendall marker and the inter-diffusion coefficient in solid Cu/solid Ni diffusion couples increased with increasing magnetic flux density in case of the direction of diffusion parallel to B; (2) The migration of the Bi/Bi0.4Sb0.6 interface due to the self-diffusion of the liquid metal into the solid alloy decreased markedly with the increase of magnetic flux density; (3) High magnetic fields exerted a non-monotonic influence on the thickness of diffusion layers during the reactive diffusion process between liquid Al and solid Cu; (4) The application of a high magnetic field during chemical reactive-diffusion process of gas Al/solid Cu system induced a significant change in the final products.
Single Photon Generation from Nitrogen Atomic-Layer Doped Gallium Arsenide
Authors: Takamiya Kengo , Endo Yuta , Fukushima Toshiyuki , Yagi Shuhei , Hijikata Yasuto , Mochizuki Toshimitsu , Yoshita Masahiro , Akiyama Hidefumi , Kuboya Shigeyuki , Onabe Kentaro , Katayama Ryuji , Yaguchi Hiroyuki
Published: January 2012

We have studied the properties of photoluminescence (PL) from individual isoelectronic traps formed by nitrogen-nitrogen (NN) pairs in nitrogen atomic-layer doped (ALD) GaAs. Micro-PL measurements were performed to investigate the properties of single photons generated from individual isoelectronic traps. Twin PL peaks were observed from individual isoelectronic traps in nitrogen ALD GaAs (001). The PL transitions at longer and shorter wavelength sides were linearly polarized in the [110] and [1-10] directions, respectively. The peak splitting and polarization properties can be explained by some in-plane anisotropy most likely due to strain in host crystal. From individual isoelectronic traps in nitrogen ALD GaAs (111), a single PL peak with random polarization was observed, showing that the growth on (111) surface is an effective way to obtain unpolarized single photons. As for nitrogen ALD GaAs (110), different polarization properties were obtained depending on the atomic configuration of NN pairs. In addition, we have used AlGaAs layers to diminish the in-plane anisotropy and could successfully obtained single emission lines with unpolarized character. Introducing AlGaAs layers was also useful for improving the luminescence efficiency.
Dynamic Resistance Based Model for On-Line Resistance Spot Welding Quality Assessment
Authors: El Ouafi Abderrazak , Belanger R. , Guillot Michel
Published: January 2012

On-line quality assessment becomes one of the most critical requirements for improving the efficiency of automatic resistance spot welding (RSW) processes. Accurate and efficient model to perform non-destructive quality estimation is an essential part of the assessment. Besides the usual welding parameters, various measured variables have been considered for quality estimation in RSW. Among these variables, dynamic resistance (DR) gives a relative clear picture of the welding nugget formation and presents a significant correlation with the RSW quality indicators (QI). This paper presents a structured approach developed to design an effective DR-based model for on-line quality assessment in RSW. The proposed approach examines welding parameters and conditions known to have an influence on weld quality, and builds a quality assessment model step by step. The modeling procedure begins by examining, through a structured experimental design, the relationships between welding parameters, typical characteristics of the RD curves and multiple welding QI. Using these results and various statistical tools, different integrated quality assessment models combining an assortment of DR attributes are developed and evaluated. The results demonstrate that the proposed approach can lead to a general model able to accurately and reliably provide an appropriate assessment of the weld quality under variable welding conditions.
Specific Energy as a Characterizing Parameter for Laser Welded Ti-5Al-5V-5Mo-3Cr Alloy
Authors: Shariff Tasneem , Cao Xin Jin , Chromik Richard R. , Gholipour Javad , Wanjara Priti , Cuddy Jonathan , Birur Anand
Published: January 2012

In this study, specific energy was calculated and correlated with the geometries, defects, microstructures, hardness values and tensile properties of the laser welded Ti-5553 alloy. It was found that specific energy is a good parameter to characterize the laser welding process.
Microstructural Characterisation of Railhead Damage in Insulated Rail Joints
Authors: Rathod C. , Wexler D. , Chandra T. , Li H.
Published: January 2012

As an integral part the railway network infrastructure, insulated rail joints (IRJs) electrically isolate track segments providing critical feedback to both track signaling and train position detection systems. Because of the discontinuous nature of IRJs, accumulated damage at the railhead is high. Failure modes include plastic flow of metal across joints, bolt and fishplate failures, delamination of insulated material and, as a result of rolling contact fatigue, end post and endpost surface damage. In the current investigation, microstructural changes in the vicinity of endposts of IRJs made from both surface coated and uncoated rail are investigated using techniques of optical and scanning electron microscopy. Damaged IRJs made from pearlitic head hardened rail steel are compared with head hardened rail steel laser coated with martensitic stainless steel, the latter having an increased service life. Problems associated with the surface coating are identified and approaches to further improving IRJ resistance to rolling contact fatigue suggested. Keywords: Insulated rail joints, rail, head hardened, surface coated rail
Effect of Strain Rate on Hydrogen Evolution during Deformation in Al-Zn-Mg Alloys
Authors: Horikawa Keitaro , Yamada Hiroyuki , Mutsuo Masahide , Kobayashi Hidetoshi
Published: January 2012

Hydrogen gas evolution behaviour during deformation and fracture in Al-Zn-Mg alloys with and without copper additions was examined by using a testing machine equipped with a quadrupole mass spectrometer in an ultrahigh vacuum chamber (QMS-UHV) and by a hydrogen microprint technique (HMT). The QMS-UHV testing revealed that hydrogen gas was evolved at the moment of grain boundary fracture, in particular. This suggested that hydrogen atoms primarily dissolved were trapped at the grain boundaries before the fracture. It was also revealed that hydrogen gas evolution behaviour was changed according to the testing strain rate. The HMT also revealed that silver particles, which represented the emission sites of hydrogen, were observed mainly around the second phase inclusions and the grain boundaries.
Experimental and Numerical Investigation of Residual Stress and Distortion Control during Welding of AISI-316L Plates
Authors: Pazooki A.M.A. , Hermans M.J.M. , Richardson I.M.
Published: January 2012

Welding residual stress and subsequent distortions are a common problem during fabrication. Several techniques for controlling residual stress and distortion during welding, amongst which transient thermal tensioning is one of the more promising methods. Thermal tensioning can be achieved by two side heaters moving along with the weld heat source. The concept of transient thermal tensioning induces a redistribution of the stress field in the welded plate by altering the thermal field. In this paper, the results are presented on the mitigation of out-of-plane deformation during gas tungsten arc butt welding of 2 mm thick AISI-316L stainless steel. Acetylene-air burners are applied as side heaters. The thermal tensioning process induces a number of additional process parameters including the intensity, the size and the location of the heaters. A thermo-mechanical (TM) finite element model is used to cope with the complexity of the process. The model provides a better understanding of the development of the stress field, both in conventional and transient thermal tensioned welds and of the mechanisms which mitigate distortion. The model is validated by temperature, stress and distortion measurements. It appears that the redistribution of stresses and the introduction of tensile stresses by side heating is the main mechanism responsible for the reduction of distortion.
Laser Joining of Metal and Plastic Using Insert Materials
Authors: Hino Makoto , Mitooka Yutaka , Murakami Koji , Kanadani Teruto
Published: January 2012

Laser joining for dissimilar materials between metals plate and polypropylene plate using a newly developed insert sheet was investigated. It was not possible to join the plate of various metals to the nonpolar plastic plate such as the polypropylene directly under the various laser-irradiation conditions. However, the use of insert sheet held between the metal plate and the polypropylene plate made it possible to join each metal plate to polyethylene plate by laser-irradiation. The joining strength increased with the increase in the input energy by laser-irradiation, and the joining strength cloud be improved since the reactivity between each metal and the insert material allows improvement by giving the insert material polarity with such as a-NH2 group, -COOH group.
Low Temperature Sintering Bonding Process Using Ag Nanoparticles Derived from Ag2O for Packaging of High-Temperature Electronics
Authors: Hirose Akio , Takeda Naoya , Konaka Yosuke , Tatsumi Hiroaki , Akada Yusuke , Ogura Tomo , Ide Eiichi , Morita Toshiaki
Published: January 2012

A novel bonding process using Ag2O paste composed of Ag2O particles and a reducing agent has been proposed as a Pb-free alternative of high melting point solders in electronics packaging. Ag2O paste formed Ag nanoparticles through the redox reaction in the bonding process and in-situ formed Ag nanoparticles sintered immediately. While the bonding process using Ag metallo-organic nanoparticles, which have been proposed, was unfavorable to the bonding at 250 degree Celsius or lower in terms of requiring removal of stable organic shells, the bonding process using Ag2O paste demonstrated the possibility of further low-temperature bonding.
Dissimilar Metal Joining of Steel to Aluminum Using the Arc Heat Source
Authors: Kim Yong , Park Ki Young , Kim Yune Soo , Kim Seok Jin
Published: January 2012

Car manufactures have been asked to avoid the unnecessary waste of energy and reduce pollution. Replacing steel with lightweight materials on car bodies is considered as one method to reduce the vehicle weight to achieve these requirements. Therefore, in this study, we selected a modified metal inert gas welding-brazing process to join aluminum to zinc coated steel on the lap geometry. The main purpose of this research was to reveal the relationship between weldability and various process parameters such as Zn coated thickness, kind of coated treatment type, filler wire type and welding condition. Metallurgical observations and mechanical testes were carried out to evaluate the weld quality. Based on these results, we could find that the weldability of dissimilar materials were depend on sufficient and regular wetting by heat input and gap condition. The tensile-shear test results, all the fracture occurred in the HAZ of aluminum and the strength was up to 70% of base metal of aluminum. However zinc coated thickness in the range of 10㎛ to 30㎛ was no related with welded strength. Also we could find that silicon content of filler wire is very important to minimize the thickness of intermetallic compound layer. Silicon might be disturbed to the growth intermetallic compounds.
Effect of Water Cooling on Grain Structures and General Mechanical Properties of 2219-T6 Friction Stir Welded Joint
Authors: Liu Hui Jie , Zhang H.J. , Yu L.
Published: January 2012

Regarding the friction stir welding (FSW) of heat–treatable aluminum alloys, although the thermal flow does not cause any material fusion, it can still deteriorate the local mechanical properties of the joints due to coarsening or dissolution of the strengthening precipitates. Therefore, it is of significance and possible to improve the joint properties by controlling the temperature level. For this purpose, a 2219-T6 aluminum alloy was underwater friction stir welded in the present study, and the temperature histories, grain structures and the general mechanical properties of the joints were investigated in order to illuminate the effect of water cooling. The results reveal that the water cooling action can effectively control the temperature level in the joint. The recrystallized grains in the weld nugget zone (WNZ) are significantly refined under the water cooling effect. The mechanical analysis indicates that the tensile strength of the joint can be improved by 6% through the external water cooling action. Additionally, the underwater joint also exhibits superior bend and impact properties to the normal joint, indicating the positive effect of water cooling on the general mechanical properties of the joints.
Hybrid Laser-Arc Welding of HSLA-65 Steel Plate: Microstructural and Mechanical Property Evaluation of Butt Welds
Authors: Munro Cameron , Nolting Allison E. , Cao Xin Jin , Wanjara Priti
Published: January 2012

High strength low alloy (HSLA) steel, namely HSLA-65, has shown promise as a replacement for more common high strength shipbuilding steels. However, conventional high heat input welding processes can cause significant distortion, often requiring expensive post-weld reworking. Butt welds in HSLA-65 steel were fabricated using a hybrid fibre laser-gas metal arc welding (GMAW) procedure to investigate the efficacy of distortion mitigation via low heat input joining. Heat input from the laser and arc sources were roughly equal at ~5.2 kW each, and plates were welded in either the laser-leading or arc-leading configuration. In either case, butt welds in ~9 mm thick plates could be made in a single pass at a total heat input of ~0.4 kJ/mm. Welding induced distortion was minimal. Analysis of the microstructure and microhardness of the welds is provided, along with some preliminary results of mechanical and impact testing.
Optimization of Laser Welding Parameters in Aluminum Alloy Welding and Development of Quality Monitoring System for Light Weight Vehicle
Authors: Park Young Whan , Kim Dong Yun
Published: January 2012

In this paper laser welding AA5182 of aluminum alloy with AA5356 filler wire were performed with respect to laser power, welding speed, and wire feed rate. The experiments showed that the tensile strength of the weld was higher than that of the base material under sufficient heat input conditions. A genetic algorithm was used to optimize process parameters which were the laser power, welding speed, and wire feed rate. To do that, a fitness function was formulated, taking into account weldability and productivity. A factor for the weldabilty used tensile strength estimation model which was made by neural network, and as the productivity, welding speed, and wire feed rate were used. Weld monitoring system for aluminum laser welding with filler wire was constructed through the optical sensors to measure the plasma light intensity. Relationship between monitoring signal and plasma and keyhole behavior according to welding condition was analyzed and it was found that sensor signal could express the information for weld quality. Weld quality estimation algorithm was formulated fuzzy multi feature pattern recognition algorithm using the monitoring signals. Quality prediction system was also developed to apply this algorithm to production line.
Resistive Implant Welding of Advanced Polymers
Authors: Rodríguez-Senín E. , de la Mano Rubén , Blanco Lourdes
Published: January 2012

Resistive Implant Welding involves an electrically conductive implant (welding rod) placed between the parts to be joined. Heat generation by Joule effect raises the temperature of the implant above the melting temperature of the thermoplastic being joined and a weld is reached. In the present study, resistive implants have been used to weld two HDPE components that make up a tank. RIW represents a good welding technique for advanced thermoplastic polymers contributing to increase the use of those materials and their industrial applications.
Development of Low Temperature Bonding Technique of Titanium and Zirconium Using Hydrogen Diffusion-Induced Phase Transformation
Authors: Saida Kazuyoshi , Ogiwara Hiroyuki , Nishimoto Kazutoshi
Published: January 2012

A new bonding technique of titanium and zirconium conducted at low temperatures was developed utilizing the hydrogen-induced transformation. Hydrogen charge treatment of the faying surfaces of titanium and zirconium was conducted with varying the charging time between 3.6-700ks prior to diffusion bonding. Diffusion bonding of hydrogen-charged titanium and zirconium was carried out at 600-800°C for 0.6-1.8ks applying the bonding pressure of 5-10MPa in vacuum. Titanium and zirconium hydrides were formed at faying surfaces after hydrogen charge treatment. The β-transus temperature at faying surfaces of titanium and zirconium was reduced to approx. 450-550°C with hydrogen-charging. The bond layer was phase transformed to a bcc structure (β) at the bonding temperature due to the hydrogen diffusion during bonding process. Grain growth across the prior bond interface was observed in the joints bonded at 750-800°C after hydrogen-charging for 300-500ks. Tensile strength of titanium joints bonded at 800°C attained approx. 70% of the base metal strength (approx. 1.6 times as high as non-charged joints), and corrosion resistance of the joints was comparable to that of the base metal. Furthermore, tensile strength of zirconium joints bonded at 800°C was approx. 1.7 times as high as non-charged joints. It follows that the solid-state bondability of titanium and zirconium at low temperatures was improved compared to the conventional diffusion bonding (direct bonding without hydrogen-charging).
Preliminary Investigation on Friction Spot Welding of AZ31 Magnesium Alloy
Authors: Campanelli L.C. , Suhuddin U.F.H. , Dos Santos Jorge Fernandez , Alcantara N.G.
Published: January 2012

Friction spot welding (FSpW) is a recent solid state welding process developed and patented by GKSS Forschungszentrum (now Helmholtz-Zentrum Geesthacht), Germany. A spot-like connection is produced by means of an especially designed non-consumable tool consisting of pin, sleeve and clamping ring that creates a joint between sheets in overlap configuration through frictional heat and plastic deformation. FSpW offers many advantages over conventional spot joining techniques including high energy efficiency, surface quality and environmental compatibility. Comparing with friction stir spot welding, FSpW produces a weld without keyhole on the surface at the end of the joining process. In the present study, the possibility of joining AZ31 magnesium alloy by FSpW technique was evaluated by using different welding parameters (rotational speed, plunge depth and dwell time), aiming to produce high quality connections. Microstructural features were analyzed by light optical microscope and mechanical performance was investigated by microhardness test and lap shear test. Microstructure analysis revealed that defects free welds could be produced. A slight decrease in grain size of the stir zone was observed causing a slight increase in the microhardness of this region. The preliminary lap shear data demonstrated that the weld strength is comparable to other welding process.
Linear Friction Welding of a Single Crystal Superalloy
Authors: Wanjara Priti , Dalgaard Elvi , Gholipour Javad , Larose Joel
Published: January 2012

The effect of forging pressure on linear friction welding (LFW) behaviour of a single crystal Ni-based superalloy was investigated. Crystal orientations of the specimens were controlled and results indicated that welding success is dependent on proximity of the oscillation direction to the <011> direction. Characterization of the welds included optical examination of the microstructural features of the weld and thermomechanically affected zones (TMAZ) in relation to the parent material. Mechanical properties of the welded material examined via microhardness testing showed an increase in strength in the weld zone (WZ). Microstructural examination indicated that some recrystallization occurred in the WZ, as well as a small amount of distortion of the dendrites in the TMAZ. With increased forge pressure, recrystallized grains remaining in the weld were minimized.
Microstructure and Wear Characteristics of Fe-Based Hard-Facing Alloy Claddings Formed by Gas Tungsten Arc Welding
Authors: Lin C.M. , Wu W.
Published: January 2012

The current investigation discusses the effect of Mn and Si contents on the microstructure and abrasive wear characteristic in Fe-based hard-facing alloy. A series of Fe-based hard-facing alloys are successfully fabricated onto the S45C steel by gas tungsten arc welding (GTAW). Results reveal that microstructure contains great amounts of martensite phases and moderate amounts of austenite phases. Si element added into Fe-based hard-facing alloy can not obviously affect the properties of the claddings, such as martensite phase, hardness, and abrasive wear resistance. Nevertheless, Mn element added into Fe-based hard-facing alloy can efficiently affect the martensite phase, hardness, and abrasive wear resistance of the claddings. The martensite contents decreases with the increasing of Mn contents in the cladding layers. The hardness increases as the Mn contents decreases, because the martensite contents increases. The abrasive wear resistance is not only related to the hardness of the cladding layer but the martensite contents of the cladding layer. The abrasive wear resistance is an inverse proportion to Mn contents of the cladding layers. Especially, the cladding layers containing 1.4Si-0.3Mn has the highest hardness of HRC 60.1 and the lowest wear loss of 0.37g.
Effect of Heat Treatments and Small Addition of Fe on the Occurrence of Serration in Al-Zn Alloys
Authors: Kanadani Teruto , Nakagawa Keiyu , Sakakibara Akira , Murakami Koji , Hino Makoto
Published: January 2012

The effect of heat treatment conditions and small addition of Fe on occurrence of serration in Al-Zn alloys was investigated. Specimens were aged for various times up to 5Ms at 293K or 273K after quenching from various temperatures (TQ), 398K to 853K, and tensile-tested at room temperature. Serration occurred more easily according as TQ became lower and the aging time became shorter: in the case that TQ=473K serration was observed even after aging for 2.6Ms, while in the case that TQ=773K serration did not occur irrespective of aging conditions. Serration was also recognized when the specimens were furnace-cooled from 773K to room temperature. Thus, for the binary alloy serration was observed only when the aging period was short enough, but addition of Fe to the binary alloy prolonged the aging period where serration could be recognized. Aging rate measured by hardness was remarkably retarded with the increase of Fe addition. These results together with those obtained by the electrical resistometry suggest that the serration in Al-Zn alloys occurs in the early stage of aging where small GP zones or solute clusters are formed.
Effect of Copper Variation and Thermomechanical Treatment on Microstructure and Properties in Aluminum Alloy Fin Stock for Heat Exchanger
Authors: Kang Suk Bong , Kim Dong Bae , Cho Jae Hyung
Published: January 2012

Aluminum alloys are commonly used as a material for heat exchangers due to their higher thermal conductivity and specific strength among various metallic materials. Twin roll strip casting process is considered to produce the high quality and low manufacturing cost aluminum alloy fin stock for automobile heat exchangers. Thermomechamical treatment has carried out to obtain optimum processes for initial cold rolling, intermediate annealing and final cold rolling, which can meet the requirements for high strength and high thermal conductivity after brazing heat treatment. Additionally the effect of copper element variation was considered to determine the optimum content of copper element in Al-Zn-Mn-Si-Fe-Cu based alloys produced by twin roll strip casting process. Mechanical properties and thermal condutivity have been evaluated before and after simulated brazing process. The nuclei of recrystallization might be formed along shear deformation bands during initial cold rolling and should be grown during intermediate annealing to enhance the permeation of molten brazings for the following brazing process. Final cold rolling has allowed strain hardening and controlling of sagging amount as fin stock materials of heat exchanger. In the present study the suitable thermomechnical treatment and optimum copper content was suggested to balance the properties of strength, thermal conductivity, brazing behaviour, corrosion resistance and sagging resistance in Al-Zn-Mn-Si-Fe-Cu based alloys produced by twin roll strip casting process.
Precipitation in Al-Alloy 6016 – The Role of Excess Vacancies
Authors: Falahati Ahmad , Lang Peter , Kozeschnik Ernst
Published: January 2012

6xxx Al alloys owe their superior mechanical properties to the precipitation of finely dispersed metastable β´´ precipitates. These particles are formed in the course of optimized heat treatments, where the desired microstructure is generated in a sequence of precipitation processes going from MgSi co-clusters and GP zones to β´´ and β´ precipitates and finally to the stable β and Si diamond phases. The entire precipitation sequence occurs at relatively low temperatures (RT to approx. 200 °C) and is mainly controlled by the excess amount of quenched-in vacancies, which drive the diffusional processes at these low temperatures. Very recently a novel model for the prediction of the excess vacancy evolution controlled by the annihilation and generation of vacancies at dislocation jogs, grain boundaries and Frank loops was developed and implemented in the thermo-kinetic software MatCalc. In the present work, we explore the basic features of this model in the simulation of the excess vacancy evolution during technological heat treatments. The focus of this article lies on the effect of vacancy supersaturation during different heat treatment steps, such as quenching, heating, natural and artificial aging.
Through Process Microchemistry Effects on the Properties of 8xxx Sheet
Authors: Schneider Wolfgang , Laptyeva Galyna , Lentz Martin , Karhausen Kai F.
Published: January 2012

In commercial 8xxx alloys several material characteristics such as softening behaviour, strength and technological ductility are influenced by alloying elements in their solute and precipitated form (i.e. microchemistry). Depending on the thermo-mechanical processing conditions a spectrum of microchemistry states (including variations of solute level, phase volume fraction, phase morphology) and therefore a spectrum of possible microchemistry-microstructure interactions can be obtained and used for a set up of sheet properties. In the present paper, the impact of homogenization conditions on the microchemistry development in selected 8xxx alloys is discussed with a view of controlling final properties. Effect of the processing route on the microchemistry evolution is demonstrated using the statistical Classical Nucleation and Growth (ClaNG) model.
The Effect of Erbium on the Properties and Microstructure of Al Alloys
Authors: Nie Zuo-Ren , Huang Hui , Gao Kun Yuan , Li Bo Long , Wang Wei , Chen Zi Yong , Rong Li , Wen Sheng Ping , Li Hong Mei , Zuo Tie Yong
Published: January 2012

Mechanical properties, corrosion resistance, and microstructure of Al alloys with trace element erbium were studied. Systemic studies in the pure aluminum and 5xxx series Al alloys showed that the tensile strength was significantly improved by above 20% with little loss of elongation by Er alloying. The 5xxx series Al alloys with erbium also exhibited excellent corrosion resistance. Erbium improved the aging hardness response of 7xxx series Al alloys and the addition of 0.4%Er to Al-Zn-Mg alloys increases the hardness by 35MPa. In all experiment Al alloys, a small addition of 0.1wt% Er induced a quick increase of the tensile strength and the amount of 0.4%Er shows optimized balance of the strength and ductility. The Er addition improved the thermal stability, with increasing the starting Rex temperature about 50°C in all investigated Al alloys. With regard to the microstructure mechanisms, in all experimental Al alloys Er addition has significantly refined the microstructure, which mainly attributed to presence the Al3Er particles. In the 7xxx series Al alloys, no observable PFZ after addition of 0.4% Er was found. The fatigue property, the fracture toughness and the thermal stability of microstructure and properties are on the way.
Microstructure and Properties of an Al-7.5Zn-1.5Mg-1.4Cu-0.12Zr Alloy Forging
Authors: Li Xi Wu , Xiong Bai Qing , Zhang Yong An , Li Zhi Hui , You Jiang Hai , Yin Xiao Hui , Fan Yun Qiang , Zhu Bao Hong
Published: January 2012

In this present work, the microstructure and properties of an Al-7.5Zn-1.5Mg-1.4Cu-0.12Zr alloy forging in T7452 condition has been investigated by means of OM, TEM and EBSD analysis and varied properties test. The results indicate that there are obvious differences in grain morphology, precipitation characteristics and recrystallization degree along the thickness direction of the forging. The strength of the alloy forging is stable and varies less than 10% along the thickness direction. The alloy forging in the T7452 condition shows high strength, high toughness and good corrosion resistance, with the UTS, TYS, elongation and electrical conductivity values being 500~530 MPa, 460~500 MPa, 7.0~15.0% and 23.9~24.2 MS/m, respectively, and the fracture toughness in L-T, T-L and S-L direction being 33.5~39.5, 25.5~27.0, 23.0~24.5 MPa.m1/2, respectively, and the EXCO rating being EA.
Research on Multi-Artificial Aging Applied to Aluminum Alloy 7150 Plate
Authors: Li Zhi Hui , Xiong Bai Qing , Zhang Yong An , Lu Xin Yu , He Zhen Bo , Jin Long Bin , Li Xi Wu , Han Xiao Lei
Published: January 2012

The AA 7150-T351, in the form of 40 mm thick plates, was subjected to single-stage aging leading to peak aged condition, and two selected multi-artificial aging treatments leading to the over aged conditions. The microstructural differences along the thickness direction of the AA 7150-T351 plate were investigated using OM and electron backscatter diffraction (EBSD) technique, and the microstructural characterization was studied at different stages of multi-artificial ageing process by transmission electron microscopy. Tensile properties and electrical conductivity measurements were used to evaluate the property homogeneity along the thickness direction of the plate under various artificial aging tempers. It was revealed that the microstructural features and tensile property are inhomogeneous in different layers along the thickness direction, and both grain structure and tensile property exhibit appreciable anisotropy at the same thickness layer. The volume fraction of recrystallized grain of T351 plate in the near surface layer is higher than that in the center layer remarkably. It is also shown that two selected multi-artificial aging tempers can provide optimal precipitates in matrix and at grain boundaries, which gives rise to a combination of high strength and stress corrosion cracking (SCC) resistance in such materials.
Investigation on Quench Sensitivity of a Heat-Resistant Aluminum Alloy
Authors: Lu Xin Yu , Li Zhi Hui , Wang Guo Jun , Zhang Yong An , Xiong Bai Qing
Published: January 2012

The quench sensitivity of 2D70 aluminum alloy was investigated by end-quenching. The effect of water temperature on quench sensitivity was studied by measuring the hardness and conductivity. The end-quenching characteristics of hardness and conductivity of 2D70 aluminum alloy under different water temperatures has been described. The end-quenching characteristics of 2D70 and 2124 alloy under the same condition have been compared and analyzed. The results show that the susceptibility of 2D70 alloy to quenching is slow and the differential effects of the water temperatures of 16°C and 30°C on end-quenching of this alloy are not obvious. The quench depth of the alloy is more than 150mm.
Combined Effect of Deformation and Precipitation on Tensile Properties of an Al-Mg-Si Alloy
Authors: Kolar Michal , Teichmann Katharina , Gulbrandsen-Dahl Sverre , Pedersen Ketill Olav , Marthinsen Knut
Published: January 2012

In the present work we report on the effect of pre-deformation followed by/together with artificial aging on the mechanical properties as strength, ductility and work hardening of an Al-Mg-Si alloy (AA6060). The AA6060 alloy was initially cast, homogenized and extruded according to standard industrial practice. The extruded material was then subjected to a solution heat treatment and subsequently artificially aged after (sequential mode) and during (simultaneous mode) various combinations of deformation (0-10%) and heat treatments. The aging behaviour and mechanical properties have been characterized in terms of Vickers hardness and tensile testing. It is found that small, even very small, pre-deformations strongly affect the aging behaviour and associated tensile properties. Moreover, it is found, that with the carefully chosen parameters of simultaneous deformation and aging one can reach mechanical properties superior to those following pre-deformation and subsequent aging (sequential mode). The results are compared and discussed in view of differences in processing conditions and microstructure characteristics.
Effect of Additional Elements (Cu, Ag) on Precipitation in 6xxx (Al-Mg-Si) Alloys
Authors: Matsuda Kenji , Nakamura Junya , Kawabata Tokimasa , Ikeno Susumu , Sato Tatsuo , Marioara Calin D. , Andersen Sigmund J. , Holmestad Randi
Published: January 2012

It has been known that Cu- or Ag-addition Al-1.0mass%Mg2Si (balanced) alloys shows higher hardness and elongation than Cu-free or Ag-free balance alloy. In this study, the alloys with Cu or Ag addition and the alloys with Si / Mg in excess have been investigated by hardness and tensile tests and HRTEM observation. Cu addition is effective for higher hardness, and Ag-addition is useful for improvement of elongation for peak-aged samples. Precipitates in peak aged these alloys have been confirmed by HRTEM. Cu-addition alloy almost includes Q’-phase, and Ag-addition alloy includes b’-phase. The precipitation sequence of Ag- or Cu addition Al-Mg-Si alloy was investigated using HRTEM, SAED, and EDS. The precipitates obtained in the two alloys were classified into several kinds by HRTEM images and SAED patterns. The relative frequencies of precipitates were also investigated and compared with that in the alloy.
Effect of the Thermomechanical Processing on Microstructure and Properties of an Al-Ce Alloy
Authors: Mogucheva Anna , Zyabkin Dmitriy , Kaibyshev Rustam
Published: January 2012

Effect of equal channel angular pressing (ECAP) at room temperature and subsequent annealing at temperatures ranging from 450 to 600°C on microstructure, mechanical properties and electric conductivity of an Al-8%Ce alloy was examined It was shown that Al4Ce-type eutectic particles having plate-like shape break under ECAP; distribution of the particles appears to be more homogeneous. ECAP leads to about two-fold increase in yield stress (YS) and ultimate tensile strength (UTS); ductility and electric conductivity decrease significantly. Under following annealing, the spheroidizing and coagulation of Al4Ce-type particles occur extensively resulting in decreased strength and increased electric conductivity and ductility.