bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of Crystal Structure and Crystallographic Features of NiMnGa Thin Films by Combination of X-Ray Diffraction (XRD) and Electron Backscatter Diffraction (EBSD)
Authors: Yang Bo , Li Zong Bin , Zhang Yu Dong , Esling Claude , Qin Gao Wu , Zhao Xiang , Zuo Liang
Published: May 2014

In this work, NiMnGa thin film composed of non-modulated martensite (NM) and seven-layered modulated martensite (7M) was produced. The crystal structure and lattice constants were determined by X-ray diffractometer (XRD). The preferred crystallographic orientation of martensite was determined using the four-circle XRD. SEM/EBSD was employed to verify the crystal structure of the martensite and to reveal its crystallographic features correlated with the microstructure. According to the XRD patterns, the crystal structure of NM and 7M was determined as tetragonal and monoclinic crystal structure, respectively. Pole figures measured by four-circle diffractometer revealed that the NM martensite possesses (004)NM and (220)NM preferred plane texture close to the substrate surface, whereas the 7M martensite has (2 0 20)7M, (2 0 )7M and (040)7M preferred plane texture close to the substrate surface. SEM/EBSD analysis shows that the surface layer of the film is mainly composed of NM martensite that is organized in variant groups. In each variant group, all the martensite plates consist of paired lamellar (112)NM compound twins and there are eight orientation variants in each variant group.
Formation of Multiple Twinned Structural Units in Electrodeposited Nickel after Annealing
Authors: Kahrimanidis Alexander , Klement Uta
Published: May 2014

Electrodeposition is an advanced synthesis technique which involves the creation of a coating or free-standing material through an electrolytic process. Organic additives such as saccharin have been frequently used in electroplating operations to moderate deposit growth rates and to control film quality. In the present study, plating of Nickel without additives has resulted in a sub-microcrystalline microstructure and a <110>-fibre texture in growth direction. Structural units in form of groups of grains possessing a common <110>-zone axis in growth direction and low-Σ relationships between them have been found in the microstructure by use of EBSD. Upon annealing, grain growth sets in. However, the structural units and the texture are preserved up to 550°C. This means that the structural units stabilize the microstructure; there is no orientation change when grain growth occurs (e.g. by twinning). The low-Σ boundaries of the structural units are described in detail and texture development upon annealing is discussed in connection with results from previous studies on Ni and Ni-alloys of different initial texture.
Disorientation Relations during the Early Stages of Recrystallization in Medium and Low SFE fcc Metals
Authors: Miszczyk M. , Paul Henryk , Driver Julian H. , Maurice Claire
Published: May 2014

The objective of this paper is to identify the predominant crystallographic relations between deformed state and recrystallized grains during the early stages of recrystallization of fcc metals with medium and low stacking fault energy. The experimental investigations, based on SEM/EBSD measurements, have focused on the transformations which occur in plane strain compressed single crystals with stable orientations. After annealing the disorientation across the recrystallization front 'defines' the final rotation by angles in the ranges of 25-35o and 45-55o around axes mostly grouped near the <122>, <012>, <112> and <111> directions located around the normals of all four {111} slip planes.
Effect of the Channel Angle of One-Pass ECAP Prior to Cold Rolling on the Microstructure and Texture of Metallic Sheets
Authors: Miyamoto Hiroyuki , Ueda Masashi , Hiroshi Fujiwara
Published: May 2014

Equal-channel angular pressing (ECAP) was applied to 16mass%Cr steel sheets for one pass prior to cold rolling in order to improve formability and alleviate ridging of the sheets. Effect of channel angle of ECAP (90° and 120°) on the deformation microstructure and the subsequent recrystallization was focused. One-pass ECAP indeed modified the cold-rolled microstructures, texture and subsequent recrystallization as compared with that in cold rolling alone. In particular, grain-scale shear bands were introduced during ECAP in otherwise hard-to-recrystallize <001>//ND grains by ECAP, and they facilitated the recrystallization. However, the effect of reducing the channel angle from 120°to 90°on the recrystallization and the formability was limited in spite of higher shear strain imposed on the sheets.
Structure and Fatigue Properties of Cr-Ni-Ti Austenitic Steel after Equal Channel Angular Pressing
Authors: Dobatkin Sergey V. , Skrotzki Werner , Terent’ev Vladimir , Rybalchenko Olga , Belyakov Andrey , Prosvirnin Dmitry , Zolotarev Eugenie
Published: May 2014

After equal channel angular pressing (ECAP) at room temperature in 08%C-18%Cr-10%Ni-Ti steel grain-subgrain structure with the size of structural elements of 100-250 nm, volume of high angle boundaries (HAB) about 59% and 38% of martensite is formed. ECAP at 400°C results in fully austenitic structure with the structural element size of 100-400 nm and volume of HAB ~54%. ECAP increases the ultimate tensile strength of 08%C-18%Cr-10%Ni-Ti steel by 1.5 - 2 times, the yield stress by 3.8 - 5.2 times, the fatigue limit - by 1.4 - 1.7 times, however the ductility is reduced. Fatigue strength is enhanced by the refinement of the structure and twinning in the austenite during ECAP and due to intensive dynamic twinning, partial martensitic transformation and increasing of the volume of HAB during cyclic deformation.
Processing Different Magnesium Alloys through HPT
Authors: Malheiros Livia Raquel C. , Figueiredo Roberto B. , Langdon Terence
Published: May 2014

High-Pressure Torsion (HPT) is widely used to refine the structure of metallic materials through the use of severe plastic deformation. This technique is used in this report to process different magnesium alloys using various processing conditions. The high hydrostatic pressure allows processing of these materials at room temperature without cracking. The structure was characterized and hardness distribution was determined at different areas of the processed samples. The results show significant structure refinement and increased hardness. The evolution of the structure and hardness depends on the alloying and HPT processing conditions.
Consolidation of High Performance AA6061 and AA6061-SiCp Composite Processed by High Pressure Torsion
Authors: El-Garaihy W.H. , Rassoul El Sayed M.A. , Salem Hanadi G.
Published: May 2014

Discs of monolithic AA6061 and AA6061 reinforced with SiCp were processed via combination of hot compaction of the mixed powders followed by high pressure torsion (HPT). HPT processing was investigated using incremental revolutions up to four, under pressures of 1 and 3 GPa. Structural evolution of the powders before and after HPT processing was investigated using scanning electron microscope (SEM). HPT processing of AA6061 discs produced a trimodel structure with micron-scale grains, subgrains and nanoscale substructure of 29, 1.9 μm, and 250 nm, respectively. Reinforcement with SiCp resulted in a refined structure with micron-scale grains, subgrains and nanoscale substructure of 25, 1.9 μm, and 184 nm respectively. The presence of SiCp at the triple junctions and along the grain boundaries enhanced the rate of strain hardening of the Al-matrices and significantly refined the grain size. More pronounced refinements of the grains, subgrains, and substructures were observed with increasing the HPT pressure up to 3 GPa.
The Role of Cr in H Desorption Kinetics in Rapidly Solidified Al
Authors: Tashlykova-Bushkevich Iya I. , Horikawa Keitaro , Itoh Goroh
Published: May 2014

Hydrogen desorption kinetics for rapidly solidified high purity Al and Al-Cr alloy foils containing 1.0, 1.5 and 3.0 at % Cr were investigated by means of thermal desorption analysis (TDA) at a heating rate of 3.3°C/min. For the first time, it was found that oxide inclusions of Al2O3 are dominant high-temperature hydrogen traps compared with pores and secondary phase precipitates resulted in rapid solidification of Al and its alloys. The correspondent high-temperature evolution rate peak was identified to be positioned at 600°C for high purity Al and shifted to 630°C for Al-Cr alloys. Amount of hydrogen trapped by dislocations increases in the alloys depending on Cr content. Microstructural hydrogen trapping behaviour in low-and intermediate temperature regions observed here was in coincidence with previous data obtained for RS materials using thermal desorption spectroscopy (TDS). The present results on hydrogen thermal desorption evolution indicate that the effect of oxide surface layers becomes remarkable in TDA measurements and show advantages in combinations of both desorption analysis methods to investigate hydrogen desorption kinetics in materials.
Effect of Microstructure State of Titanium Alloy Ti-6Al-4V on Structure and Mechanical Properties of Joints Produced by Diffusion Bonding Process
Authors: Lopatin Nikolay , Senkevich Kirill , Kudryavtsev Egor A.
Published: May 2014

The studies of diffusion bonded samples of Ti-6Al-4V and Nitinol alloys were carried out considering the titanium alloy in two states: ultra-fine grained and bi-modal microstructures, the last one consisted of small and large α-phase grains. Depending on microstructure and chemical composition of the alloys, the diffusion bonding had been made at temperatures from 600°C to 850°C. The microstructures of joints was studied by scanning electron microscope using detector of backscattering electron diffraction. The shear strengths of joints were measured. It was concluded that the ultra-fine grained Ti-6Al-4V alloy could be applied for joints manufactured at a temperature lower than 750°C. The bi-modal Ti-6Al-4V alloy is an effective material for producing the joints at the temperature larger that 750°C.
Effect of Process Control Agents (PCAs) on Mechanochemical Processes and Contamination Science
Authors: Shiba Daisuke , Yamasue Eiji , Ishihara Keiichi N. , Okumura Hideyuki
Published: May 2014

Mechanochemical (MC) processes are often modified to a large extent with use of process control agents (PCAs). An appropriate PCA is, however, chosen semi-empirically for any MC process such as ball-milling. In this study, milling period and medium, PCA kinds and amount, and powder kinds, are altered as major parameters to systematically and mechanistically investigate the effect of PCAs on powder milling and the related phenomena. The model systems selected are TiO2 and ZnO powders with various PCAs including alkanes, alcohols, water, and a few ionic liquids. According to X-ray line broadening analyses the viscosity and the structure of PCA molecules strongly affect the MC process. In addition, the MC process for harder TiO2 is quite different from ZnO, and oxygen-derived polarity of PCA molecules would cause major difference on the milling behavior. Various parameters controlling the MC process will be discussed.
Mössbauer Spectroscopy of Grain Boundaries in Ultrafine-Grained Metal Materials
Authors: Popov Vladimir V.
Published: May 2014

Capabilities of the Mössbauer (nuclear gamma-resonance) spectroscopy for investigation of the state of grain boundaries in ultra-fine grained materials are analyzed, and the main problems of such studies are discussed. The emission and absorption NGR spectroscopy are compared, and it is demonstrated that the emission mode of the Mössbauer spectroscopy is preferential for GB studies. These studies enable to reveal differences in the state of GBs in ultra-fine grained materials and coarse-grained polycrystals with GBs of recrystallization origin.
Microstructure Evolution and Creep Behavior in ECAP Processed Metallic Materials
Authors: Sklenička Václav , Král Petr , Dvořák Jiří , Kvapilová Marie , Svoboda Milan
Published: May 2014

The creep behavior of high purity aluminum and copper, Al-0.2wt.%Sc and Cu-0.2wt.%Zr alloys was examined after processing by equal-channel angular pressing (ECAP) with an emphasis on the link between microstructure and creep. The microstructure was revealed by electron backscatter diffraction (EBSD) and analyzed by stereological methods. Representative microstructural parameters were obtained using orientation imaging microscopy and EBSD on the relationship between creep behavior and microstructure.
High Strength Microscrew with Ultrafine Grained Structure
Authors: Torizuka Shiro , Muramatsu Eijiro
Published: May 2014

While uniform elongation is a measure of ductility of the material, reduction in area in tensile tests is also an important measure of ductility. It was found that the reduction in area - tensile strength balance is far better than the conventional ferrite+pearlite steels and even superior to martensitic and bainitic steels. Formability of ultrafine-grained steel is examined by applying to form a M1.7 micro screw using these ultrafine-grained steels. Screws are formed through the process of cold heading and rolling. Relationship between cold heading, rolling, uniform elongation and reduction in area are investigated to clarify the formability of ultrafine-grained steels. Low-carbon ultrafine-grained steel has excellent cold headability and favorable rolling properties, i.e., excellent formability. Reduction in area is a measure to determine formability on cold heading. Ultrafine grained steel wire with length of several hundred meter were developed with the technology of warm continuous multi-directional rolling. This wire also have a good formability which can form microscrews. High strength microscrew with ultrafine grained structure was obtained.
Mechanical Properties of High-Manganese Austenitic TWIP-Type Steel
Authors: Dobrzański Leszek Adam , Borek Wojciech , Mazurkiewicz Janusz
Published: May 2014

Taking into consideration increased quantity of accessories used in modern cars, decreasing car’s weight can be achieved solely by optimization of sections of sheets used for bearing and reinforcing elements as well as for body panelling parts of a car. Application of sheets with lower thickness requires using sheets with higher mechanical properties, however keeping adequate formability. The goal of structural elements such as frontal frame side members, bumpers and the others is to take over the energy of an impact. Therefore, steels that are used for these parts should be characterized by high value of UTS and UEl, proving the ability of energy absorption. Among the wide variety of recently developed steels, high-manganese austenitic steels with low stacking faulty energy are particularly promising, especially when mechanical twinning occurs. Beneficial combination of high strength and ductile properties of these steels depends on structural processes taking place during cold plastic deformation, which are a derivative of SFE of austenite, dependent, in turn on the chemical composition of steel and deformation temperature. High-manganese austenitic steels in effect of application of proper heat treatment or thermo-mechanical treatment can be characterized by different structure assuring the advantageous connection of strength and plasticity properties. Proper determinant of these properties can be plastic deformation energy supply determined by integral over surface of cold plastic deformation curve. Obtaining of high strength properties with retaining the high plasticity has significant influence for the development of high-manganese steel groups and their significance for the development of materials engineering.
Advanced TSV Filling Technology for 3-Dimensional Electronic Packaging
Authors: Lee Chang Woo , Ko Young Ki , Ko Yong Ho , Bang Jung Hwan
Published: May 2014

The development of 3D integration is necessarily required for high speed, high density, small size, and multi-functional electronic devices. Through silicon via (TSV) technology has been rapidly developed to fulfill the demand of the next generation of multifunctional electronic systems as one of the most alternative applications for 3D packaging. In this study, low cost and high speed molten solder-filling of TSV and bonding process by using micro bump was investigated. Micro bumps were formed with two step, Cu pillar bump and Sn-Ag cap bump by using electroplating. The size of micro-bumps was 10 and 20um and the precise content of the bump was developed with good planarity by adding reflow process. Additionally, the SiC nanoparticle composite solder was fabricated for low CTE filling material. From the results, it is possible that the CTE of composite solder added 1.0wt% SiC nanoparticles had decreased until 15.0ppm/°C. Comparing CTE of pure Sn, which was about 24.0ppm/°C, it was very low CTE and lower then CTE of Cu (16.5ppm/°C). Even if the electrical resistance of nanopowder composite solder is increased, the increasing rate is very slow until 1.0 wt%. However, the resistance changing rate is rapidly increased over the 1.0wt%. From the result, it is expected that nanopowder composite solder can contribute high reliability of molten solder filling TSV.
Effects of Material Property and Structural Design on the Stress Reduction of the Joints in Electronics Devices
Authors: Matsushima Michiya , Nakashima Noriyasu , Fujimoto Takashi , Fukumoto Shinji , Fujimoto Kozo
Published: May 2014

Electronics devices consist of silicon chips, copper leads, substrates and other parts which are jointed to each other with solder, conductive adhesive or other materials. Each coefficient of thermal expansion is different and it causes strain concentrations and cracks. We analytically investigated the stress reduction structure at the edge of the joints such as Sn-Ag-Cu solder or Cu/Sn alloy between the silicon chip and copper lead. At first, we examined the influence of the joint thickness and fillet at the joint edge on the stress. In the joint without fillet, the stress at the end of the joint increased depending on the thickness of the joint. The fillet of the joint increased the stress of the Cu/Sn alloy joint and the stress was increased depending on the thickness, though the fillet decreased the stress of the solder joint. We suggested the copper lead with slits to reduce the force of constraint. We compared the effects of the structure parameters of the slits on the stress reduction. The height was a more effective parameter than the width and the pitch. In the case of solder joint, the slits of the copper lead reduce the stress more effective in the thick joint than the thin joint. However, in the case of Cu3Sn joints, the slits reduced the stress more effectively in the thin joint than thick joint.
Laser Beam Welding for Reduced Activation Ferritic/Martensitic Steel F82H
Authors: Mori Hiroaki , Ogiwara Hiroyuki , Saida Kazuyoshi , Serizawa Hisashi , Hirose Takanori , Tanigawa Hiroyasu
Published: May 2014

A fusion reactor is expected as one of the new electric power sources in next generation. Reduced activation ferritic/martensitic steel F82H is planned to be used as a structural material for the blanket modules set on the inner wall of the reactor. However, especially in the case of laser beam welding (LBW), the weldability of the steel was not completely clarified. On the other hand, although post weld heat treatment (PWHT) should be conducted for the welds of the steel in accordance with general standards for chrome steels, the heat treatment conditions were uncertain. Therefore, adaptability of LBW as a joining method for the steel and the applicable PWHT conditions for the welded joints were investigated in this study. The effect of LBW conditions on weld penetration behavior were ascertained by observation of cross sections in the welds. The adequate PWHT conditions were confirmed in consideration of both hardness distributions measured in welds and ductile-brittle transition temperatures (DBTT) evaluated using Charpy impact test. Full penetration without weld defects such as hot cracking, porosity etc. was obtained for plates with the thickness of 4mm of the steel by control welding conditions. That means laser beam is one of useful welding heat sources to realize sound weld joints of the steel. In addition, due to select appropriate PWHT conditions, the hardness in welds was suppressed to the level of base metal and the toughness in the welded joints was improved to a practical level without the damage to base metal.
Microscale Evaluation of Mechanical Properties and the Interfacial Microstructures of Friction Stir Welded Aluminum Alloy/Stainless Steel Dissimilar Lap Joints
Authors: Ogura Tomo , Nishida Taichi , Nishida Hidehito , Fujimoto Mitsuo , Hirose Akio
Published: May 2014

The mechanical properties and interfacial microstructure of slices of friction stir welded aluminum alloy/stainless steel dissimilar lap joints were characterized. In an FSWed A3003 aluminum alloy/SUS304 steel lap joint, the strength on the advancing side was larger than that at the retreating side. TEM observation indicated that a sound joint that fractured at the base metal can be obtained from the stage of the formation of the amorphous layer owing to the mechanical alloying effects before the formation of intermetallic compounds. This lap joining technique was also successfully applied to A6061/T6 aluminum alloy-grooved SUS304 plates. Equiaxed aluminum grains were observed at the interface of the specimen after it was fractured, indicating that the interface deformed only slightly during the microtensile test. It was found that tensile strength of the joint was increased by aging at 433K, considering that precipitation occurred at this temperature. In addition, it was confirmed that the joint heated at 723K for 1.8ks still fractured at the aluminum matrix, assuming that intermetallic layers at the interface would slightly grow in this heating condition.
Enhanced Weld Penetrations in GTA Welding with Activating Fluxes Case Studies: Plain Carbon & Stainless Steels, Titanium and Aluminum
Authors: Rückert Guillaume , Perry N. , Sire Stéphane , Marya Surendar
Published: May 2014

Flux applications prior to the convention Gas Tungsten Arc Welding (GTAW) is known to improve weld penetrations and improve process competitiveness. This paper summarizes the investigations on aluminum, plain carbon steels, stainless steels and titanium. The importance of flux composition, homogeneity and profile of its application are shown to be primordial in determining the weld depth to width ratio of weld pools. The mechanisms that lead to improved penetrations along with some industrial case studies are presented.Key Words: ATIG, Weld penetrations, Steels, Titanium, Aluminum
A Study on the Effect of the Interpass Temperatures in Properties and Microstructures of the Alloy 625 Dissimilar Fusion Zone
Authors: Silva Cleiton Carvalho , de Miranda Hélio Cordeiro , Motta Marcelo Ferreira , Ferreira Daniel Correia Freire , Reppold Ricardo Marinho , Dalpiaz Giovani
Published: May 2014

The purpose of this study is to evaluate the effectiveness in the contribution of the interpass welding in the microstructures and properties of the dissimilar fusion zones produced with an alloy 625 and API 5L X65 steel pipes. Three multipass welded joints with v-groove, were made under the same welding parameters, therefore, changing only the interpass temperatures at: 150°C, 250°C and 450°C. The microstructural characterization was performed using the light microscopy and the scanning electron microscopy (SEM). The hardness test, charpy-V impact test and the transverse tensile test were conducted according to specific standards. The results have shown that all ruptures in the tensile tests occurred in the base metal. Both yield strengths and ultimate tensile strengths, have dropped to the 450°C interpass temperature. It was also observed a slight drop in the hardness with increasing interpass temperature. The Charpy-V impact test results showed no significant differences among the interpass temperatures. These said results indicated that the maximum interpass temperature for the alloy 625/X65 steel dissimilar welding is limited by the steel properties.
Evaluation of the Corrosion Resistant Weld Cladding Deposited by the TIG Cold Wire Feed Process
Authors: Silva Cleiton Carvalho , Afonso Conrado Ramos Moreira , Ramirez Antonio Jose , Motta Marcelo Ferreira , de Miranda Hélio Cordeiro , Farias Jesualdo Pereira
Published: May 2014

The aim of this study is to evaluate the microstructure and properties, resulting from the dissimilar welding of Ni-based alloys like Hastelloy C276 and Inconel 625 with ASTM A516 Gr 60 steel, through the deposition of overlays by the TIG welding process with cold wire feed. The results showed that it is feasible to produce coatings with low dilution levels in a single layer. Regarding the microstructure, there was a strong segregation of alloying elements during solidification. The phenomenon of microsegregation is directly or indirectly associated with the mechanism of corrosion attack. The shear resistance tests showed that coalescence between coating and substrate, provided a high shear strength, even with the possible presence of defects and high hardness martensitic zones. The immersion test in FeCl3 showed that the alloy 625 had lower CPT when compared to alloy C276. However, in the CPT temperature for the alloy C276, the intensity of the attack for the alloy 625 was lower than the alloy C276.
Hardness Prediction for Temper Bead Welding of Non-Consistent Layer Technique
Authors: Yu Li Na , Saida Kazuyoshi , Mochizuki Masahito , Kameyama Masashi , Sera Takehiko , Hirano Shinro , Nishimoto Kazutoshi
Published: May 2014

Temper bead welding (TBW) is one effective repair welding method for the large-scale nuclear power plants. Consistent Layer (CSL) technique is the theoretically most authoritative method among the five temper bead welding techniques. However in the actual operation, CSL technique is difficult to perform, and non-CSL techniques (Controlled Deposition technique, Half Bead technique, et al) are mainly used in the actual repair process. The thermal cycles in heat affect zone (HAZ) of non-CSL technique are more complicated than that of CSL techniques. Through simplifying the complicated thermal cycles to 4 types of thermal cycles, the neural network-based hardness prediction system for non-CSL techniques has been constructed. The hardness distribution in HAZ of non-CSL techniques was calculated based on the thermal cycles numerically obtained by finite element method (FEM). The predicted hardness was in good accordance with the experimental results. It follows that the thermal cycle simplification methods are effective for estimating the tempering effect during temper bead welding of non-CSL techniques.
Reinforcement of Hypereutectic Al-Si Alloys with Fe-Bearing Compounds and Si Particles Assisted with Ultrasonic Treatment
Authors: Wu Shu Sen , Lin Chong , Lü Shu Lin , An Ping , Wan Li
Published: May 2014

The hypereutectic Al-17Si-2Cu-1Ni-0.8Mn alloys with 2% or 3%Fe were fabricated out assisted with ultrasonic vibration (USV) treatment. The coarse plate-like δ-Al4(Fe,Mn)Si2 phase was transformed into fine particles with average diameter of about 17μm~20μm after USV treatment, and the volume fraction of particle-like Fe-bearing compounds is about 3.6%~5%. The polygonal primary Si crystals were also refined into particles with average diameter of about 15μm~23μm, and the volume fraction of primary Si declined to about 5.4%~6.5% after USV treatment. The matrixes of the castings were reinforced with fine Fe-bearing compounds and Si particles. The ultimate tensile strength of the alloys, which were produced by gravity casting process assisted with USV, increases with the increase of Fe content at 350 °C. It is considered the increase of the elevated temperature strength of the samples are mainly attributed to the refinement of δ-Al4(Fe,Mn)Si2 phase by USV and the increase of the volume fraction of the Fe-bearing compounds. The die casting process assisted with USV can further improve the mechanical properties of Al-17Si-2Fe-2Cu-1Ni-0.8Mn alloy.
The Numerical and Experimental Study on Electromagnet-Air Knife DC Casting Process of Large-Size AA 7055 Aluminum Alloys
Authors: Zhang Hai Tao , Cui Jian Zhong , Nagaumi Hiromi
Published: May 2014

In this paper, Low frequency electromagnetic field and air knife are applied simultaneously to produce large-size AA 7055 aluminum alloy ingots during DC casting. Moreover, the effects of low frequency electromagnetic field and air knife on macro-physical fields during DC casting as well as microstructure and crack in the ingots are studied and analyzed by the numerical and experimental methods. Comparison of the calculated results indicates that applying electromagnetic field can modify the flow direction and increase the velocity of melt flow and homogenize the distribution of temperature in the sump, and applying air knife can homogenize the distribution of temperature and decrease the stress and strain in the solidified ingots. Further, the microstructure of the billet is refined remarkably and the crack is eliminated by applying electromagnetic field and air knife during DC casting because of modification of the macro-physical fields
The Numerical and Experimental Study on DC Casting Process of Three-Layer Composite Ingots of 4045/3004/4045 Aluminum Alloys
Authors: Qin Ke , Zhang Hai Tao , Cui Jian Zhong , Jiang Hui Xue
Published: May 2014

In this study, experiments are combined with numerical simulation to study the temperature field and flow field during the casting process of 4045/3004/4045 three-layer composite ingots with section of 500mm×420mm. The effects of casting temperature, casting speed, contacting height and cooling intensity of cooling plate on the casting process were discussed. The macro-morphologies and microstructures of the composite ingots, the temperature distribution and the element distribution in the interface zone were investigated, also the interface bonding strength was measured. The optimal parameters for casting composite ingots were obtained. Results show that the solid supporting layer formed on the cooling plates plays a key role in the casting process of composite ingots. The solid supporting layer can prevent the blending of two melts by resisting the impact of alloy melt, which ensures the stable casting process and casting high quality composite ingots.
{111}<110> Recrystallization Texture Evolution in Al-Mg-Si Alloy Sheets Fabricated by Symmetric/Asymmetric Combined Rolling Process
Authors: Inoue Hirofumi
Published: May 2014

A new rolling process, which combined asymmetric rolling with symmetric rolling, was adopted in age-hardenable 6xxx series Al-Mg-Si alloy promising as automotive body panels in order to develop favorable textures for the deep drawability after solution treatment. Symmetric cold rolling at high reduction and subsequent asymmetric warm rolling at low reduction for AA6022 sheets led to the formation of “TD-rotated β-fiber texture” including moderate {111}-oriented components, resulting in noticeable evolution of {111}<110> recrystallization texture during the solution treatment at a high temperature. The results of texture analysis and microstructural observation suggested that the low stored energy after asymmetric warm rolling, the high fraction of high angle boundaries with neighboring deformed matrices and the approximate 40° <111> orientation relationship with deformed matrices would strongly affect the evolution of {111}<110> recrystallization texture.
Room Temperature Screw Form Rolling of AZ91D Magnesium Alloy through Processing by Extrusion-Torsion Simultaneous Working
Authors: Furui Mitsuaki , Sakashita Shouyou , Shimojima Kazuya , Aida Tetsuo , Terayama Kiyoshi , Ishisaka Yusuke , Yamamoto Masayuki , Ohta Masayuki
Published: May 2014

Extrusion-torsion simultaneous processing is a very attractive technique for fabricating a rod-shape material with fine grain and random texture. We have proposed a new screw form rolling process combined with preliminary extrusion-torsion simultaneous working. Microstructure evolution and mechanical property change of AZ91D magnesium alloy during extrusion-torsion simultaneous processing was examined through microstructure observation, X-ray diffraction analysis and micro-Vickers hardness measurement. By the addition of torsion, the crystal orientation of AZ91D magnesium alloy workpiece was drastically changed from basal crystalline orientation to the random orientation. Crystal grain occurred through the dynamic recrystallization and tended to coarsen with an increase of extrusion-torsion temperature. Grain refinement under 2 um was achieved at the lowest extrusion-torsion temperature of 523 K. M8 gauge AZ91D magnesium alloy screw was successfully formed at room temperature using the extrusion-twisted workpiece preliminary solution treating at 678 K for 345.6 ks. It was found that the extrusion-torsion temperature of 678 K must be selected to fabricate the good screw without any defects.
Dynamic Transformation during the Torsion Simulation of Strip Rolling
Authors: Jonas John J. , Aranas Jr. Clodualdo , Basabe Vladimir V. , Ghosh Chiradeep
Published: May 2014

Seven-pass strip rolling simulations were carried out on a 0.06%C and a 0.09%C-0.036%Nb steel. The rolling loads (mean flow stresses or MFS’s) did not increase as the temperature decreased during the simulation. This is ascribed to the occurrence of dynamic transformation. The simulation results are compared to the high temperature flow curves determined on eight plain C and Nb-modified steels in both compression and torsion and at a series of temperatures and strain rates. When the associated MFS’s are plotted against inverse absolute temperature in the form of Boratto diagrams, the stress drop temperatures, normally defined as the upper critical temperature applicable to rolling, Ar3*, are shown to be about 40 degrees above the paraequilibrium and about 20-30 degrees above the orthoequilibrium Ae3’s. These drops are ascribed to the dynamic transformation of austenite to ferrite, a softer phase. The characteristics of the ferrite produced dynamically are described and the transformation is shown to be displacive in nature, leading to the appearance of fine Widmanstätten plates. These plates coalesce into polygonal grains on further deformation and on holding.
Microstructure and Defect Structure Evolution in Ultra-Fine Grained MgAlZn Alloy
Authors: Janeček Miloš , Stráská Jitka , Čížek Jakub , Kim Hyoung Seop
Published: May 2014

Commercial MgAlZn alloy AZ31 was processed by two techniques of severe plastic deformation, namely equal channel angular pressing (ECAP) and high pressure torsion (HPT). Microstructure evolution with strain due to ECAP and HPT was investigated by light and transmission electron microscopy (TEM). Significant grain refinement was observed in specimens processed both by ECAP and HPT. Moreover, HPT resulted in radial strain and microstructure inhomogeneity across the diameter of the sample disk. This inhomogeneity was continuously smeared out and almost homogeneous ultra-fine grained structure was observed in specimen subjected to 15 HPT rotations. Dislocation structure changes in individual specimens after different number of ECAP passes and HPT rotations were investigated by positron annihilation spectroscopy (PAS). Sharp increase of dislocation density occurred during the first two passes of ECAP, followed by the saturation and even a decline manifesting the dynamic recovery at higher strains.
Investigation of Properties of CaO Added Wrought Mg-Zn-Y and Mg-Y-Zn Alloys
Authors: Lim Hyun Kyu , Kwak Tae Yang , Yang Won Seok , Yoo Young Gyu , Kim Dae Guen , Yoon Young Ok , Kim Shae K.
Published: May 2014

In this study, the effect of CaO as alloying element on Mg-Zn-Y and Mg-Y-Zn alloys were investigated to develop wrought magnesium alloys available for aeronautic components. The evaluation for the effect of CaO addition in these alloy systems was performed by the processing map development, the tensile test, and the ignition temperature measurement. The addition of CaO changed the hot workability and improved the ignition resistance of both Mg-Zn-Y and Mg-Y-Zn alloys. Although the mechanical properties of CaO added Mg-Zn-Y alloy were lower than those of Mg-Zn-Y alloy, the CaO addition in Mg-Y-Zn alloy enhanced the ductility of the alloy. The effect of metallic Ca addition in these alloy systems were investigated to be compared with the CaO addition.
Effect of ZrB2 Nanoparticle Addition: Nano-LPSO-Grain Structured Ultra-High Strength Mg-RE Alloy
Authors: Paramsothy Muralidharan , Gupta Manoj
Published: May 2014

Currently, long period stacking/ordered phases (LPSO phases) are known to reinforceMg97Y2Zn1 type Mg-RE alloys. The LPSO phases are composed of a solid solution of Y and Znatoms placed orderly in long periods along the Mg basal plane. Also, an efficient way to strengthena polycrystalline material is to reduce its grain size. This increases the density of grain boundarieswhich impede the flow of dislocations. In many of the LPSO forming solidification processed Mg-RE alloys, the common practice is to solutionize the ingot, quench in warm water, hot extrude andthermally age. While this practice is suitable for obtaining high strength Mg-RE alloys, itconveniently employs the common idea in conventional metallurgy of fine intermetallicstrengthening while refining the grain size to within the micron regime. In this work, an alternativemethod involving boride nanoparticle addition to obtain a selected solidification processed ultrahighstrength (tensile yield strength > 400 MPa) Mg-RE alloy is discussed. Here, LPSO phaserather than fine intermetallic formation while retaining grain size under the micron regime ishighlighted.
Effect of CaO on Thermal Conductivities of Mg and Mg-Zn Alloys
Authors: Oh Gun Young , Kim Dae Guen , Yoo Young Gyu , Yoon Young Ok , Kim Shae K. , Lim Hyun Kyu , Kim Young Jig
Published: May 2014

The thermal conductivities of binary Mg-CaO and Mg-Zn, and ternary Mg-Zn-CaO alloys have been investigated by evaluating the effect of CaO on pure Mg and Mg-Zn alloys, with an emphasis to develop a new Mg alloy by compromising thermal conductivity, process-ability and mechanical property. The Mg alloys specimens were prepared by casting into a steel mold and then by machining. The thermal conductivities of the alloys were determined by evaluating the thermal properties of specific heat and diffusivity, from room temperature to 200 °C. OM, SEM, and EDS were used to analyze the microstructures and phases. The fluidity was also investigated by using a spiral fluidity mold for improved process-ability during actual die casting.
Manufacturing Technology and Usable Properties of Magnesium Alloy after Plastic Deformation
Authors: Płonka Bartłomiej , Remsak Krzysztof , Nowak Marek , Lech-Grega Marzena , Korczak Piotr
Published: May 2014

The object of this study was to develop parameters of plastic deformation in hot direct extrusion and die forging process of magnesium alloy MgAlZn. Extrusion process was conducted in the temperature range 350°C÷450°C at different extrusion speeds (ram speed 0.5 mm/s÷3 mm/s). The extrusion tests have showed that for this alloy it is possible to use the temperature of the extruded material ranging from 350°C÷450°C when the process is run at the optimum ram speed. Higher temperature of extrusion is beneficial For higher ram speed of 3mm/s, in this alloy at a temperature of 420÷450°C, cracks began to show in the surface. The same problem were for die forging. Extruded rods and forging parts were characterized by mechanical properties and structure in different heat treatment tempers. This magnesium alloy obtained in the T5 temper higher mechanical properties then T6 temper. The paper also presents research results of investigation of conversion coating on MgAlZn magnesium alloy by anodic oxidation method in non-chromium solutions. It was found that the coating produced in non-chromium solutions show considerable increase of corrosion resistance of tested alloy.Keywords: Mg alloys, extrusion, mechanical properties, structure, corrosion resistance.
Hot Forging of Cast Magnesium Alloy TX31 Using Semi-Closed Die and its Finite Element Simulation
Authors: Rao Kamineni Pitcheswara , Suresh Kalidass , Prasad Yellapregada Venkata Rama Krishna , Hort Norbert , Kainer Karl Ulrich
Published: May 2014

Magnesium alloys based on Mg-Sn-Ca system have shown improved corrosion and creep properties. In this type of alloys,Sn forms a solid solution with Mg that improves the corrosion resistance while Ca forms thermally stable intermetallic phases in the matrix enhancing the creep resistance. The Sn to Ca ratio is an important variable in deciding the type of intermetallic phases that form in the microstructure.In Mg-3Sn-1Ca alloy (TX31), a single intermetallic phase CaMgSnforms, which is responsible for its improved creep strength.With a view to evaluate its forgeability,isothermal forging experiments of TX31 were conducted on a hydraulic press in the temperature range of 350 °C to 500 °C and at speeds of 0.01 mm s-1to 10 mm s-1 using a semi-closed die. Finite-element (FE) simulation of the forging process was also conducted using the software DEFORM 2D to obtain the local variations of strain and strain rate. The effectivestrain values are below2.4 in the forged components and the forging loads predicted using FE simulation correlated well with the experimental data for all the forging conditions. The microstructures of the forgings show that CaMgSn phase is well distributed in the matrix which exhibited dynamically recrystallized microstructure as predicted by the processing map.
Microstructure Evolution of Mg-10Gd-2Y-0.5Zn-0.3Zr Alloy during Isothermal Forging Process
Authors: Shan De Bin , Han X.Z. , Xu Wen Chen
Published: May 2014

The isothermal forging process of a bracket and its microstructure evolution of Mg-10Gd-2Y-0.5Zn-0.3Zr alloy have been investigated in the present study. The results show that the bracket with thin-web and high-rib is well formed through modifying corners and adding an active damping block into male die. Amounts of lamellae and particles distribute uniformly on the matrix after the isothermal forging process and ageing process. The isothermal forging process has an obvious effect on the precipitation behaviour of secondary phases, while it did not change the grain size greatly. With the increase of ageing time, more secondary phases precipitate from α-Mg matrix until 60h. The optimal ultimate tensile strength and elongation of the peak-aged alloy are 382MPa and 4.03%, respectively. The combined effects of LPO and β′ phases contribute to the high strength of the peak-aged alloy.
Relaxation of Misfit Dislocations at Nodes
Authors: Shao Shuai , Wang Jian , Misra Amit , Hoagland Richard G.
Published: May 2014

Experimental studies proved that structures and properties of misfit dislocations and their intersections (nodes) in semi-coherent interfaces strongly affect thermal and mechanical stability of interface. Employing atomistic simulations, we reveal that misfit dislocation lines can exhibit a spiral pattern (SP) or remain straight in association with dislocation character at nodes. By analyzing nodes formation processes in terms of kinetics and energetics, we found that the variation is ascribed to the competition between core energy of misfit dislocation and interface stacking fault energy with respect to coherent interface.
Microstructure Change of AZCa912 Magnesium Alloy Continuous Casting Bar by Hot Compression
Authors: Watazu Akira , Omura Naoki , Miwa Kenji , Saito Naobumi
Published: May 2014

AZCa912, 8.8mass%Al-0.68mass%Zn-0.25mass%Mn-1.9mass%Ca-Bal.Mg, continuous casting bars were formed and their hot compression properties were measured. AZCa912 alloy is a noncombustible magnesium alloy. AZCa912 bars 50 mm in diameter were formed by a direct chill continuous casting method. The surfaces of the bars had excellent metallic luster. Grain sizes in the bars were 148, and the dendrite arm spacing was 16.9 μm. Cracks on the side surfaces of the samples were formed by compression at 250-300°C, 0.01-1/s and 350°C, 1/s. However, inner cracks were not observed and-5 μm fine-grains were formed. Some samples had an unchanged casting structure after hot pressing, and the percent of the structure remaining unchanged decreased with low-temperature compression.
Twin Roll Casting and Rolling of New Mg-Wrought Alloys for Body Protective Safety Equipment
Authors: Wendt Joachim , Bronfin Boris , Stutz Lennart , Kurz Gerrit , Schmitt Sabrina , Bamberger Menachem , Letzig Dietmar
Published: May 2014

Currently magnesium alloys are used for different applications in the transportation industry where cast magnesium alloys dominate the market. Although cast alloys predominate over wrought products such as extrusions, forgings, sheet and plate, the latter are also being used in a variety of different applications. Recently, a growing interest in the automotive industry in looking at potential applications for magnesium turned back towards wrought alloys. Typically, applications of magnesium sheets are sought in automotive or aeronautics industry. However, the spectrum of potential applications can be significantly expanded. For example, body protection systems for civil services like police, custom officers and prison personnel currently include anatomically shaped aluminium alloy sheets. Replacement of aluminium alloys by magnesium to result in substantial weight savings up to 30%.
Effect of Microstructure on Hot Bulging Deformation for AZ31 Magnesium Alloy Sheet with Resistance Heating
Authors: Zhang Kai Feng , Liu Jing Yuan , Li Chao
Published: May 2014

To enhance the heating efficiency and the formability of AZ31 magnesium alloy, the assistance heating method is adopted during the hot bulging process. The free bulging test of coarse grained and fine grained AZ31 magnesium alloy sheet was carried out. During the forming process, the effects of pulse current on the formed sheet combine both thermoelectricity and electro-plasticity. Directional and asymmetrical deformation of the coarse-grained AZ31 magnesium alloy sheet by the effect of pulse current is observed and analyzed. But in the same processing condition, the deformation of fine grained AZ31 magnesium alloy sheet is symmetrical. To investigate the influence of electron wind force on pulse current auxiliary bulging process, the simulation of AZ31 magnesium alloy pulse current auxiliary bulging based on the electron wind force value calculated by mathematical model was performed using the Marc software. The bulging simulation result showed a special phenomenon that the shape of the bulging specimen is unsymmetrical and the dome deviated from the symmetry axis to the side of positive pole. The simulation results were basically consistent with the experimental results. The deformation properties, microstructure characteristics, dislocation movement of the AZ31 magnesium alloy during gas bulging processing by the pulse current are investigated.
Modelling of the Ductile Damage Behaviour of a Beta Solidifying Gamma Titanium Aluminide Alloy during Hot-Working
Authors: Halici Dilek , Prodinger Daniel , Poletti Cecilia , Huber Daniel , Stockinger Martin , Sommitsch Christof
Published: May 2014

Gamma titanium aluminides are innovative materials for high temperature and light weight applications [1]. On the other hand, their hot workability can be limited by failure during hot deformation processes. The prediction of ductile damage in metallic materials can be performed by macromechanical ductile damage criteria [2-4]. If the calculated damage D parameter exceeds a critical value Dc, the material fails. Some macromechanical ductile damage criteria are shown in Table 1, with σ as effective stress, ε as effective strain, σmax as maximum principal stress, σm as hydrostatic stress (mean stress) and εf as equivalent fracture strain. The damage responds to strain localization and thus, to multiaxial stress concentration that increases fracture probability.