bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Study on Parametric Analysis of μEDM of Non-Conductive Ceramics
Authors: Ojha Nirdesh , Zeller Florian , Müller Claas , Reinecke Holger
Published: May 2014

Characterized by excellent material properties such has high mechanical, thermal and chemical stability technical ceramics such as ZrO2, SiC, Si3N4 and AlN are increasingly being used for various applications. Traditional means of machining sintered ceramics are expensive and limited by geometry. Electrical discharge machining (EDM) is an electro-thermal machining process used to structure conductive materials. By applying a conductive layer (denoted as assisting electrode) on top of the non-conductive material, the EDM process can also be used to structure insulating ceramics. This paper presents a comparative study on the major machining parameters affecting the µEDM process of non-conductive SiC, ZrO2, Si3N4 and AlN ceramics. The influence of five major machining parameters (current, open-circuit voltage, gap voltage, duty-cycle and servo) over two responses (material removal rate (MRR) and tool wear rate) is investigated for each ceramics material. The underlying reason for the variation in the MRR among the different ceramics is examined by comparing the material properties. Melting point of the ceramics material has an effect on the MRR for the µEDM of different ceramics. The bulk resistance value of the ceramic material does not have an influence on the MRR for the µEDM of different ceramics. Scanning electron microscope (SEM) images of the cross section of the unprocessed and µEDM processed surface of these ceramics have been analyzed. The SEM micrographs show that the µEDM process does not affect the ceramics bulk. It also confirmed spalling as one of the dominant material removal mechanism for ZrO2 ceramics.
Fluid-Particle Separation of Magnetorheological (MR) Fluid in MR Machining Application
Authors: Ismail I. , Aqida Syarifah Nur
Published: May 2014

The presented work is an investigation of fluid-particle separation phenomena and compression stress resistance performance of magnetorheological (MR) fluids under squeeze mode. The squeeze mode is very significant to MR machining application. Material used in this study was silicone oil based MR fluid with 20% volume fraction of carbonyl iron particle. Compression test was performed by integrating the developed squeeze mode testing rig with a 50 kN Universal Testing Machine (UTM). The tests were conducted at constant speed and current. Each test was conducted at an initial gap of 2 mm and was stopped at a final gap of 0.5 mm. Force-displacement data was recorded and was analysed using TestExpert® II software. Full factorials with 27 experiments were designed using Design Expert 7 software. Three factors investigated in the design of experiments were carrier fluid viscosity, supplied current, and compression speed. Responses measured were strain energy and compression stress at maximum strain. Macro images of the phenomenon were recorded and evaluated qualitatively. From the compression stress-strain results, carrier fluid viscosity was significant to vary the MR fluid properties. The observed phenomenon shows that fluid-particle separation occurred in the low viscosity carrier fluid, low compression speed and high applied current. The parameters effect on strain energy and compression stress suggests that the fluid-particle separation is significant to the squeeze mode MR fluid performance. The relationship between stress resistance performance and fluid-particle separation phenomena were significant in designing innovative MR fluid devices.
Friction Stir Welding Assisted by Electrical Joule Effect to Overcome Lack of Penetration in Aluminium Alloys
Authors: Santos Telmo Gomes , Miranda Rosa M. , Vilaça Pedro
Published: May 2014

Friction stir welding assisted by electrical joule effect is a development of conventional friction stir welding with the ability to eliminate or minimize the root defects by lack of penetration. The lack of penetration, mainly relevant in the welding of aluminium alloys, still constitute one major constrain to a wider dissemination of friction stir welding into industrial applications. The concept is based on assisting friction stir welding by an external electrical heat source integrated in the FSW tool. The innovative tool feature enables to increase the temperature in the weld root by Joule effect and improve material viscoplasticity in this region. A new tool was designed, manufactured and implemented. The resulting welds produced were analyzed via metallography and Electrical conductivity measurements that have proven to be a valuable technique to identify the different zones of solid-state welded joints with a good correlation with the microstructure and hardness. The potential of this variant was shown reducing the thickness of weld root defect, even for significant levels of lack of penetration, although affecting the grain size of the HAZ in the vicinity of the root surface.
Modeling the Adhesion Bonding Mechanism in Overmolding Hybrid Structural Parts for Lightweight Applications
Authors: Giusti Ruggero , Lucchetta Giovanni
Published: May 2014

Reducing vehicle weight to decrease energy consumption and engine emissions is one of the major objectives of the automotive industry today. This goal is mainly achieved by developing new manufacturing technologies for structural lightweight components, such as the hybrid injection molding/composite forming process, which involves preforming a thermoplastic composite laminate and overmolding it to add ribs, attachment points and other features. High part lightness, short cycle times and high degree of automation have recently made this technology an effective solution for the manufacturing of automotive interiors, including door side-impact beams and front ends. In this paper a model of the adhesion bonding mechanism between the overmolded reinforced thermoplastic and the formed composite sheet is proposed, and its dependence on the main process parameters is investigated. The model has been developed conducting experimental tests and eventually validated by means of a significant case study.
Analysis of Materials and Structures in Scientific Applications Using Micro Focus Computed Tomography
Authors: Natour Ghaleb , Pauly Fred
Published: May 2014

With an efficient system for 3D-mikrofocus-computed-tomography, the analysis of materials, welding’s, joining’s and structures, with high resolution is possible. In the research center Jülich such a tomographic system is available and has been developed continuously for a wide range of applications. The field of work of the X-ray system and the applications ranges from the analysis of organic materials up to solid metal components like welding’s and joining technologies. The image acquisition is carried out by novel flat panel detectors. The performance of the 3D visualization is demonstrated using examples from various scientific areas and applications. The system makes it feasible to extend automatic defective recognition (ADR) also on a real-time basis. By the special construction and the choice of its components, in combination with individually developed software tools, different application spectra are possible, e.g. for rapid prototyping or reverse engineering as well as FEM analysis in real components.
Investigation on Internal Stress of SU-8 Photoresist Film
Authors: Zhang Xiao Lei , Du Li Qun , Zhu Shen Miao
Published: May 2014

In this paper, substrate curvature method was adopted and a theory model based on Stoneys formula was built for obtaining the internal stress of SU-8 film. The effect of substrate diameter, film thickness and post-baked temperature on substrate curvature ratio was investigated by ANSYS simulation. The analytical result shows that post-baked temperature is the main effect factor on internal stress of SU-8 film. In addition, internal stresses of SU-8 at three different post-temperatures (55°C, 70°C and 85°C) are measured. The results show that the experimental results greatly agreed with simulation analytical results. It means the internal stress of SU-8 film can be accurately described by the theory model, which provides a basis for the quantitative analysis of the internal stress in SU-8 film.
Study on the Calibration of Dynamic Balancing Machine for Separating System Interference Vibration
Authors: Deng Shan , Zhao Ding Ding , Cai Ping
Published: May 2014

The minimum achievable residual unbalance ratio emaris the index for evaluating the balancing capability of dynamic balancing machine. When the emaris expected to achieve to 0.1um grade or higher, to tap potential solely from the design of the signal conditioning circuits or the digital signal processing algorithm could not settle problems completely, equal importance should be paid on eliminating the influence of machine intrinsic interference vibration. Unfortunately, compared with much effort on the research and implementation of circuits and algorithm for unbalance signal extraction, little attention has been paid on the latter. This paper puts forward an interference vibration separation approach based on multi-point test-mass circulation calibration, to the purpose of improving the overall performance of balancing machine.The measurement system of a dynamic balancing machine composed of vibration mechanism, vibration pick-up sensor, signal conditioning circuits and the digital signal processing module, wherein the vibration mechanism locates on the front end and is of great importance. In the current design of dynamic balancing machine, there is a hypothesis that the vibration mechanism vibrates in the manner of simple harmonic oscillation forced by the unbalance of the under test rotate work piece and the amplitude and initial phase of that vibration are only related to the magnitude and angle position of the unbalance. In a practical balancing machine, however, the unbalance of driving devices, the coaxial error of the coupling or the vibration of the driving belt will incur additional vibrations to the vibration mechanism. Being of the same frequency or nearby frequency with the unbalance vibration, those interference vibrations are difficulty to remove by the signal conditioning circuits or the digital signal processing approach.Based on the invariability of the machine intrinsic interference vibration, this paper developed a circumference multi-point measurement and compound calibration method. The principle of the method will be introduced and analyzed in detail in the paper. Based on the vector operation and least square fitting to the unbalance vibration response with the obtained compound vibrations, the interference vibration can be separated to a satisfied extent. Experiments investigation is carried out on a hard bearing dynamic balancing machine, and the experiment results demonstrate the feasibility of the said method.
Cost-Efficient Measurement System Analysis for Small-Batch Production
Authors: Schmitt Robert , Wiederhold Michael , Damm Juliane , Harding Martin , Jatzkowski Philipp , Ottone Renato
Published: May 2014

This paper presents an approach for the selection of methods for the proof of capability of measurement processes according to the risk connected to a false decision. High risks demand more reliable and therefore cost-intensive methods, a low risk allowing for cost-efficient methods with lower reliability. This approach, which is incorporated into the upcoming guideline VDI/VDE 2600-1, allows manufacturers to reduce efforts and costs associated with measurement process evaluation according to the risks and consequences of erroneous decisions deriving from measurement results. To be able to decide for the economically optimal measurement process solution, a cost model for the processes described in the VDI/VDE 2600-1 is presented.
Corrosion Resistance of Al-Cu Alloys in Function of the Microstructure
Authors: Román Alejandra Silvina , Méndez Claudia Marcela , Ares Alicia Esther
Published: May 2014

Aluminum and its alloys are characterized by low density, high electrical and thermal conductivity, and good resistance to corrosion in certain media such as air. The mechanical strength alloy is achieved. The objective of the present research consist on studying the type of structure (columnar, equiaxed or with columnar to equiaxed transition, CET) using parameters of the solidification process and electrochemical parameters in Al, Cu and Al-Cu alloys with different concentrations. In order to obtain columnar, equiaxed and CET structures, the alloys were directionally solidified upwards in an experimental set up with a set of thermocouples in the samples which permit to determine the time dependent profiles during the process. The electrochemical studies of the samples were realized by using an electrochemical impedance spectroscopy (EIS) technique and potentio-dynamic polarization curves immersed in 3% NaCl solution at room temperature. In general, we observed that the susceptibility to corrosion of the different structures depends on the size of the secondary dendritic spacing and the proportion of Al2Cu phase and Al-rich phase.
Static Grain Growth in an Austenitic Stainless Steel Subjected to Intense Plastic Straining
Authors: Tikhonova Marina , Belyakov Andrey , Kaibyshev Rustam
Published: May 2014

The post-dynamic recrystallization of an ultrafine grained 304-type austenitic stainless steel was studied during annealing at 800 and 1000°C for 7.5 to 480 minutes. The initial ultrafine grained microstructures have been developed by continuous dynamic recrystallization during isothermal multidirectional forging to a total strain of ∼4 at temperatures ranging from 500 to 800°C. The post-dynamic recrystallization involves a rapid softening at early stage of annealing followed by a sluggish decrease of hardness upon further annealing. A transient recrystallization at early annealing stage results in somewhat heterogeneous microstructures in the samples subjected to previous deformation at relatively low temperatures of 500-600°C. This structural heterogeneity disappears with increasing the annealing time. Commonly, the post-dynamic recrystallization behavior can be considered as a kind of continuous recrystallization.
Slip System Analysis in the Cold Rolling of a Ni3Al Single Crystal
Authors: Demura Masahiko , Raabe Dierk , Roters Franz , Eisenlohr Philip , Xu Ya , Hirano Toshiyuki , Kishida Kyosuke
Published: May 2014

The activated slip systems were analyzed in the cold rolling of a Ni3Al single crystal with an initial orientation of ~[-112](512), which showed an irregular rolling deformation, i.e. widening, bending, and shear deformation. A phenomenological crystal plasticity model was applied using a spectral method. The boundary condition was optimized to reproduce the actual rolling deformation, as follows. That is, the orthogonal components of the deformation gradient were given from the measured widening and reduction, and the shear components were iteratively optimized as to that the final orientation was as close to the experimental one as possible. The calculated result showed that three slip systems, a3, b1, and d1 in the Bishop-Hill notation, were mainly activated in the irregular rolling deformation, which result was consistent to the previous observation of the slip traces [Kishida et al., Philos. Mag. 83 (2003) 3029]. The three activated systems were identical to those activated in the plane-strain condition. However, the quantitative comparison revealed that the activity of b1 was significantly reduced in the irregular rolling deformation, while the activity of d1 was enhanced instead. The less activity of b1 and the enhancement of d1 can be understood assuming a strong interaction between a3 and b1. The reaction of this pair has been reported to form the superlattice intrinsic stacking fault (SISF) in Ni3Al [Chiba and Hanada, Philos. Mag. A. 69 (1994) 751]. It is likely that the formation of the SISF, which are considered immobile in Ni3Al, restrained the activation of b1, leading to the irregular rolling deformation.
Role of Ti/Al Ratio of Ti-Al-X (X=Cr, Nb, Ta and W) Intermetallics on High Temperature Tensile Properties
Authors: Hashimoto Keizo
Published: May 2014

The mechanical properties of g-TiAl at elevated temperatures have been investigated extensively over the last 30 years. Designed alloys have been proposed from the first generation alloy (Ti-48Al-2Cr-2Nb) to the second, the third and the fourth generations. However, a decisive chemical composition of g-TiAl has not been agreed among researchers yet. The main reasons for this situation are difficulties in compositional control of Ti-Al-X-Y. In this paper, the high temperature tensile properties of g-TiAl alloy with lots of different composition have been examined from the room temperature to 1200C and the tensile strength data of those specimens have been summarized. It is clear that Ti/Al atomic ratio plays an important role on the behaviors of the high temperature strength since the Ti/Al atomic ratio is strongly related to the phase stabilities between g and a2 phases in the binary Ti-Al phase diagram. A very narrow confine of a/a2 atomic ratio exists in the specimens having the comparatively high tensile strength at the elevated temperatures. Moreover, additions of the third elements such as Cr, Nb, Ta and W to g-TiAl contribute on the increase of the tensile strength and the shift of the phase stability among a2, b and g phases. In order to utilize g-TiAl alloys in the various machine components at high temperatures, the severe process controls of melting, casting, thermo-mechanical treatments and heat treatments are indispensable.
Deformation of AA6016 Aluminum Alloy Sheets at High Temperature and Strain Rate
Authors: Bariani Paolo F. , Bruschi Stefania , Ghiotti Andrea , Michieletto Francesco
Published: May 2014

The production of aluminum alloy components through sheet forming processes conducted at elevated temperatures is gaining more and more interest as it gives raise to the possibility of a significant enhancement of the metal formability characteristics, compared to room temperature forming. However, conventional forming processes at elevated temperatures on aluminum alloy sheets are usually carried out under superplastic forming regime conditions, which are too slow to be applicable to mass production typical of the automotive industry. The aim of the present study is to investigate the formability characteristics of AA6016 aluminum alloy sheets when deformed at elevated temperature, but in a range of strain rates higher than those usually applicable in superplastic forming. To this aim, uni-axial tensile tests were carried out to evaluate both the material ductility in terms of true strain at fracture as a function of the temperature and strain rate, and the alloy post-forming characteristics after testing. In such a way, the optimal forming conditions in terms of temperature, strain rate and microstructural features were identified.
High Temperature Tensile Behavior of Directionally Solidified MAR-M247 Superalloy
Authors: Bor Hui Yun , Wei Chao Nan , Yeh An Chou , He Wei Bin , Wang Huei Sen , Kuo Chen Ming
Published: May 2014

In this study, two heat treatment schemes were proposed to study the high temperature mechanical behavior of directionally solidified MAR-M247 superalloy. Two withdraw rates, namely, 60 and 180 mm/h were used to produce directionally solidified MAR-M247 specimens by the Bridgeman type furnace. Standard heat treatment (HT1) procedures are solution treatment at 1230°C for 2 h/ArC, then first aging at 980°C for 5 h/AC and followed by second aging at 870°C for 20 h/AC. Modified heat treatment (HT2) is solution treatment at 1260°C for 3 h/ArC and first aging at 980°C for 6 h/AC, then the same second aging procedure. Uneven size, shape and fusion-alike of gamma prime precipitates are observed after full HT1 scheme, whereas even size but fine gamma prime precipitates are observed in HT2 specimen. All three tensile properties (elongation to failure, ultimate tensile strength and yield strength) of HT2 specimens are higher than these of HT1 specimens either at room temperature 25°C or at high temperature 982°C for both withdraw rates. Uneven distribution of the γ′ precipitates attributes to the initial fracture of HT1 specimens.
Spark Plasma Heat Treated ZrB2-SiC and HfB2-SiC Composites
Authors: Seetala Naidu , Webb Marquavious T.
Published: May 2014

Ultra-high-temperature ceramics (UHTC) such as ZrB2 and HfB2 with SiC nanofiller are useful for propulsion and thermal protection systems. ZrB2 and HfB2 with 10-20 wt% SiC were prepared using ultra-sonication, rotary evaporation, and spark plasma heat treatment to high temperatures (~2,000°C) and pressures (50-60 MPa). We used positron annihilation lifetime spectroscopy (PALS) to study the nanoporosity, SEM for particle size distribution, and microhardness tester for Vickers hardness. The PALS studies were performed using a 22Na positron source and the positron lifetime spectra were analyzed to three components using POSFIT program. The first and second components are related to positrons annihilating in bulk and in vacancy clusters, respectively; and the third component to positronium annihilation in nanopores within the granules. The PALS results indicate that HfB2 has larger vacancy clusters and nanopores with lesser concentrations compared to ZrB2 and SiC. The SEM observations showed that HfB2 has larger particles compared to ZrB2 and SiC showed wide range of size distribution. The Vickers-Hardness Number (VHN) is measured for spark plasma heat treated composites using a microhardness tester and the results indicate that 10wt%SiC composite has higher hardness compared to 20wt%SiC in both ZrB2-SiC and HfB2-SiC composites. HfB2-SiC composites seem to be more brittle compared to ZrB2-SiC composites. This may be due to larger size and smoother surface of HfB2 particles (600 nm) compared to ZrB2 particles (240 nm).
Microstructure and Mechanical Behaviour of NbTiAl Based Alloys Doped with Low Additions of Silicon
Authors: Zhao Zhao , Denquin Anne , Drawin Stefan , Barreau Jonathan
Published: May 2014

Nb-base refractory intermetallic materials have potential interest for high temperature applications thanks to their low density and high temperature strength. While advanced intermetallics in monolithic form have limited prospects for providing the required balance of properties for use at high temperatures, two-phase or multicomponent intermetallic systems composed of a ductile, Nb-base refractory phase in equilibrium with one or more silicide intermetallics show promise for further development as structural materials. In the present paper, Nb-base refractory alloys based on Nb-35Ti-15Al (at.%) were doped with small amount of Si (1 and 2 at% of silicon) addition to improve its high temperature strength by keeping an acceptable ductility at room temperature. The samples were prepared by arc-melting starting from pure elements (99.99%). The silicon addition effects on the microstructural features were investigated by using X Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) techniques. Its effects on the mechanical properties were assessed by compression tests at ambient and high temperatures. Compression tests show the beneficial effect of the Si addition on strength.
Characterization of the Superelasticity and the Martensitic Transformation from Ti-Nb-(O,N) Biomedical Alloys
Authors: Gloriant T. , Castany Philippe , Ramarolahy Andry , Laheute Pascal , Prima Frédéric , Curfs Caroline
Published: May 2014

In this paper, results concerning newly developed Ti-Nb based superelastic alloys containing interstitial O or N element are presented. These elements were added because of their strong influence on the alpha” martensitic transformation and also because of their solid-solution strengthening effect. Microstructures and mechanical behavior of the alloys were investigated by different methods and compared with a binary Ti-Nb alloy taken as reference. On the other hand, in-situ synchrotron X-ray diffraction analyses during tensile tests have been specifically performed to characterize precisely the stress-induced martensitic transformation in such alloys.
The Influence of Heat Treatment on the Structure and Microstructure of Ti-15Mo-xNb System Alloys for Biomedical Applications
Authors: Martins José Roberto Severino , Grandini Carlos Roberto
Published: May 2014

The Ti-15Mo-xNb system integrates a new class of titanium alloys without the presence of aluminum and vanadium, which exhibit cytotoxicity, and that have low elasticity modulus values (below 100 GPa). This occurs because these alloys have a beta structure, which is very attractive for use as biomaterials. In addition, Brazil has about 90% of the world’s resources of niobium, which is very important economically. It strategically invests in research on the development and processing of alloys containing this element. In this paper, a study of the influence of heat treatments on the structure and microstructure of the alloys of a Ti-15Mo-xNb system is presented. The results showed grain grown with heat treatment and elongated and irregular grains after lamination due to this processing. After quenching, there were no changes in the microstructure in relation to heat-treated and laminated conditions. These results corroborate the x-ray diffraction results, which showed the predominance of the β phase.
Biomedical Polymer Surface Modification of Beta-Type Titanium Alloy for Implants through Anodic Oxide Nanostructures
Authors: Hieda Junko , Niinomi Mitsuo , Nakai Masaaki , Cho Ken , Mohri Tomoyoshi , Hanawa Takao
Published: May 2014

Anodic oxide nanostructures (nanopores and nanotubes) were formed on a biomedical β-type titanium alloy, Ti–29Nb–13Ta–4.6Zr alloy (TNTZ), in order to improve adhesive strength by the anchor effect of a segmented polyurethane (SPU) with soft tissue compatibility. The nanotube structure was formed beneath the nanoporous structure. The adhesive strength between the SPU coating and the nanoporous structure formed on TNTZ by anodization is more than 1.5 times that of an SPU coating on as-polished TNTZ with a mirror finish. After removal of the nanoporous structure by etching with HF solution, the adhesive strength of the SPU coating on the exposed nanotube structure is decreased.
Fabrication of Antibacterial Titanium Implant Using Anodic Oxidation Technique
Authors: Ohtsu Naofumi , Komiya Shinji , Sakamoto Kouta , Kuji Taisuke , Sumisa Futoshi
Published: May 2014

In the present study, we demonstrated that antibacterial titanium can be simply fabricated by anodic oxidation technique, which involves connecting the Ti to the anode and then applying a direct current through the electrolyte. The substrate was soaked in 100−mM NH4NO3, 100−mM (NH4)2SO4, and (NH4)3PO4aqueous solutions, after which a constant current of 50 mA cm-2 was galvanostatically applied for 30 min. The substrate was thereafter annealed at 723 K in air for 5 h, in order to improve the crystallinity. The XRD pattern showed the layer comprised TiO2 with anatase and/or rutile type structures. All the anodized substrate could degrade methylene blue solution under ultraviolet (UV) and visible light illuminations. Antibacterial activities of the treated substrates were estimated using Escherichia coli (E.coli). The anodized Ti substrate showed sufficient antibacterial activity under weak UV light illumination with the intensity of 100 μW cm-2. In conclusion, anodic oxidation is expected as one of the promising surface treatments, in order to improve the safety of Ti devices in human use.
Plasma-Activated Electrospun Polylactide Fiber Meshes as Matrices for Tissue Engineering
Authors: Schnabelrauch Matthias , Wyrwa Ralf , Rebl Henrike , Bergemann Claudia , Finke Birgit , Schlosser Michael , Walschus Uwe , Lucke Silke , Weltmann Klaus Dieter , Nebe J. Barbara
Published: May 2014

Poly (L-lactide-co-D/L-lactide)-based fiber meshes resembling structural features of the native extracellular matrix have been prepared by electrospinning. Subsequent coating of the electrospun fibers with an ultrathin plasma polymerized allylamine (PPAAm) layer changed the hydrophobic nature of the polylactide surface into a hydrophilic polymer network and provided positively charged amino groups on the fiber surface able to interact with negatively charged pericellular matrix components. Cell experiments in vitro using different types of human epithelial cells (gingiva, uroepithel) revealed that the PPAAm-activated surfaces promoted the occupancy of the meshes by cells accompanied by improved initial cell spreading. An in vivo study in a rat intramuscular implantation model demonstrated that the local inflammatory tissue response did not differ between PPAAm-coated and untreated polylactide meshes.
Effect of Dopant Configuration on Oxygen Shielding Properties of Polycrystalline Alumina
Authors: Matsudaira Tsuneaki , Wada Masashi , Tanaka Makoto , Kagawa Yutaka , Kitaoka Satoshi
Published: May 2014

The oxygen permeability of polycrystalline α-alumina wafers, which served as model alumina layers, under an oxygen potential gradient ΔPO2 was evaluated at a temperature of 1873 K. When mutual grain boundary (GB) diffusion of oxygen and aluminum occurred in wafers subjected to a steep ΔPO2, the oxygen and aluminum fluxes at the inflow side of the wafer were significantly smaller than those at the outflow side. It was noteworthy that Lu and Hf segregation at the GBs selectively reduced the mobility of oxygen and aluminum, respectively. It was found that a wafer with a bilayer structure, in which a Lu-doped layer was exposed to a low partial oxygen pressure (PO2) and a Hf-doped layer was exposed to a high PO2, exhibited excellent oxygen shielding properties at high temperatures.
Effect of Se Content in High-Cyanide Silver Plating Solution on {200} Crystal Plane Orientation Ratio of Electrodeposited Silver Layer
Authors: Miyazawa Hiroshi , Ogata Masafumi , Shinohara Keisuke , Sugawara Akira , Shohji Ikuo
Published: May 2014

Electrodeposited silver layers obtained from high-cyanide silver plating solution are widely applied for connectors and switches of automobiles. However, few groups have discussed the relationship between the crystal structure of silver layers and their properties. In this study, the effect of the concentration of Se, added as a brightener to high-cyanide silver plating solution, was investigated by XRD and EBSD analysis for electrodeposited silver layers with {200} orientation. By optimizing the concentration of Se in the silver plating solution, the {200} orientation ratio of the silver layer was increased to as high as 94%. Since the diffusion of Cu from the Cu substrate used in this study into the silver layer was inhibited, the silver layer with the high {200} orientation ratio exhibited good electrical contact resistance of the surface of 1.3mΩ after a heating test performed at 200°C for 74h. In addition, the silver layer had good bend formability. The results of XRD analysis confirmed that the recrystallization of the electrodeposited silver layer occurred at room temperature within several hours, thus increasing the {200} orientation ratio of the silver layer.
Fabrication of Nanoporous Crystalline Alumina Membrane by Anodization of Aluminum
Authors: Ono Sachiko , Nakamura Masahiro , Masuda Tatsuya , Asoh Hidetaka
Published: May 2014

Self-ordered nanoporous α-alumina membrane having uniformly sized straight pore arrays was fabricated by anodization of aluminum and subsequent through-hole and heat treatment. The detachment of thick anodic oxide film formed in oxalic acid was performed by combining preliminary loaded heating before stepwise voltage drop and cathodic polarization in phosphoric acid to prevent excess dissolution at the through-hole process. Suppression of excess dissolution of the upper layer of anodic alumina membrane acted an important role to provide symmetrical evenness of top and bottom pore density for the prevention of deformation such as warp and cracking during subsequent heating for crystallization. Thus, a thick, robust and chemically resistant nanoporous crystalline α-alumina membrane was successfully obtained by optimizing preparation conditions.
Effect of Surface Modification on the Sound Absorption Behavior of Open Celled Aluminum Foams
Authors: Li Yun Jie , Ren Yue Lu , Li Zhen Dong , Han Fu Sheng
Published: May 2014

In the present study, needle like micro-Co3O4 rods were synthesized on the cell walls of open celled Al foam. The microstructure and phase composition of micro-rods and sound absorption properties of resultant samples were characterized. Compared with original Al foams, the modified ones showed enhanced sound absorption capacities, particularly at low frequencies, which were more obvious as the length of Co3O4 rods increased. The improvement is related to increased air flow resistance owing to increased roughness of the cell walls.
Synthesis of Physically Functionalized Carbon Nanotube Reinforced Al-Si Nanocomposite by Spark Plasma Sintering
Authors: Maiti Anway , Maurya Ram S. , Laha Tapas
Published: May 2014

Multiwalled carbon nanotube (MWCNT) reinforced Al-Si (11 wt%) alloy based nanocomposites were synthesized by spark plasma sintering using high energy ball milled nanocrystalline Al-Si powders mixed with physically functionalized MWCNTs. Improvement in MWCNT dispersion and associated improvement in densification of the nanocomposites were confirmed. The microhardness and elastic modulus of the nanocomposites measured by nanoindentation exhibited appreciable improvement. Grain size measurement by X ray diffraction and transmission electron microscopy confirmed achievement of nanocrystalline grains in Al-Si powder after ball milling, as well as in the consolidated nanocomposites. TEM analysis was performed to reveal the dislocation activity, effect of presence of primary Si and distribution of MWCNTs in the nanocomposites.
Atomic Resolution Microscopy of Nitrides in Steel
Authors: Danielsen Hilmar Kjartansson
Published: May 2014

MN and CrMN type nitride precipitates in 12%Cr steels have been investigated using atomic resolution microscopy. The MN type nitrides were observed to transform into CrMN both by composition and crystallography as Cr diffuses from the matrix into the MN precipitates. Thus a change from one precipitate type to another does not necessarily involve nucleation of the new precipitate type followed by dissolution of the old precipitates. By studying the interface between these nitrides and the matrix, it could be observed that the MN and CrMN type precipitates had a few nanometers thick amorphous layer between the crystalline nitride and ferrite matrix. Usually precipitates are described as having (semi) coherent or incoherent interfaces, but in this case it is more energetically favourable to create an amorphous layer instead of the incoherent interface.
Effect of Grain Boundary Energy Anisotropy on Faceting and Migration of Low Angle Grain Boundaries
Authors: Molodov Dmitri A. , Brandenburg Jann Erik , Barrales-Mora Luis Antonio , Gottstein Günter
Published: May 2014

The faceting and migration behavior of low angle <100> grain boundaries in high purity aluminum bicrystals was investigated. In-situ technique based on orientation contrast imaging was applied. In contrast to the pure tilt boundaries, which remained straight/flat and immobile during annealing at elevated temperatures, mixed tilt-twist boundaries readily assumed a curved shape and steadily moved under the capillary force. Computational analysis revealed that this behavior is due to the inclinational anisotropy of grain boundary energy, which in turn depends on boundary geometry – the energy of pure tilt low angle <100> boundaries is anisotropic, whereas that of mixed tilt-twist boundaries isotropic with respect to boundary inclination.
Ti and Zr Transition Metals Effect in the D03 Fe3Al by Ab Initio Study Approach
Authors: Raulot Jean Marc , Chentouf S. , Grosdidier T. , Aourag Hafid
Published: May 2014

The effect of the Ti and Zr transition metals on the D03-Fe3Al intermetallic compounds has been investigated by means of ab initio Pseudo Potentials numerical simulations based on Density Functional Theory. Two main issues will be addressed the understanding of the role of these two transition metals in terms of stability of the bulk at the light of their site preference in the D03-Fe3Al structure the behaviour of Ti and Zr transition metals in the sigma 5 (310) [001] grain boundary and their effect on the structural stability of this interface. An important issue when studying these aspects is to take into accounts the effect of temperature. This requires a molecular dynamics treatment of the atoms in the supercell. The technique known as ab initio molecular dynamics (AIMD) solves these problems by combining ‘on the fly’ electronic structure calculations with finite temperature dynamics. Thus, our study was conducted both using the conventional static ab initio calculations (0K) as well as by taking into account the effect of temperature (Ab Initio Molecular Dynamics).
Reversible Solid State Fe-Air Rechargeable Battery Using LaGaO3 Based Oxide Ion Conducting Electrolyte
Authors: Ishihara Tatsumi , Inoishi Atsushi , Ida Sintaro
Published: May 2014

The combination of solid oxide fuel cell technology with Fe-air battery concept was proposed by using H2/H2O as a redox mediator and LaGaO3 based oxide for electrolyte. Since large internal resistance and large degradation during charge and discharge cycles are observed on anode, improvement in discharge potential and cycle stability are strongly required by improving stability of anode. In this study, cermet anode consisting of Ni-Fe alloy combined with oxide ion conductor was investigated. It was found that by using cermet anode of Ni-Fe combined with Ce0.6Mn0.3Fe0.1O2 (CMF), the observed energy density of the cell is improved to be 1109 Wh/Kg-Fe at 10 mA/cm2, 873 K, which is about 92% of the theoretical energy density assuming the formation of Fe3O4 (1290 Wh/Kg-Fe). Cycle stability was also much improved on the cell using Ni-Fe-CMF anode comparing with that of Ni-Fe metal because of suppressed aggregation of Ni by mixing with CMF. Electrochemical charge-discharge measurement at 773 K showed excellent cycle stability over 30 cycles with high energy density (Round trip efficiency is higher than 80 %). The excellent performance and stability with operating at lower temperature promise this Fe-air solid oxide battery as the next generation energy storage device for averaging electricity and electric vehicle.
Fabrication of Al6061-AMC by Adding Copper-Coated SiC Reinforcement by Friction Stir Processing (FSP)
Authors: Aoh Jong Ning , Huang Chih Wei , Cheng Wei Ju
Published: May 2014

Friction stir processing (FSP) has successfully evolved as a technique in fabricating surface composite. An alternative technique on fabrication of a SiC-reinforced Al6061 aluminum matrix composite (AMC) by stirring copper-coated SiC particles into matrix to form a reinforced zone was developed. Copper film was deposited onto the SiC particles by electroless plating and by photodeposition processes. The copper coating serves as an adhesion and diffusion layer to enhance the cohesion between the particles and the matrix. It is to expect that the strength of the AMC could be improved. The uniformity of particle distribution in the stir zone (SZ) was improved by adjusting the location of particle insert and by a double-pass stir. T5 post weld heat treatment (PWHT) was conducted to retrieve the hardness and the strength of the SZ to the strength level of the matrix. While the submicron-thick Cu-coating was partially separated from SiC particles after FSP, photodeposition Cu-coating less than 100 nm thick exhibited a better adhesion to the SiC particles. The EPMA analysis across the interface shows evidence of interdiffusion between copper and aluminum which implies an enhanced cohesion between the particles and matrix. After PWHT, while the SZ containing photodeposition Cu-coated SiC exhibited the highest hardness among different SZs, the SZ containing electroless Cu-coated SiC exhibited the highest strength. The possible mechanisms for the improvement of the hardness and strength were discussed. In summary, the purpose of fabricating a locally particulate-reinforced Al6061 AMC by stirring Cu-coated SiC particles into Al6061 matrix was achieved.
Keywords:Friction stir processing (FSP), particulate reinforced AMC, electroless plating, photodeposition, copper-coated SiC particles
Effect of Friction Stir Processing on Microstructure and Mechanical Properties of a HPDC Magnesium Alloy
Authors: Cerri Emanuela , Leo Paola
Published: May 2014

A high pressure die cast (HPDC) magnesium alloy was friction stir processed (FSP) at high rotation rates with different advancing speeds. The AZ91 plate was 3 mm thick and the pin had a truncated cone tip. The friction stir processing induced the disappearance of porosity (typical of the HPDC process) in the nugget zone but some tunnel defects were introduced. The presence of characteristic FSP zones is not obvious due to the low plastic deformation of this alloy. The stirred zone is very narrow around the tool and this makes the FSP difficult to occur in the whole thickness of the plate. Microhardness values and electrical conductivity are sensitive to stirred zone and differences arise according to FSP parameters. The grain size is refined and homogenized by FSP due to partial solubilisation and disappearance of the eutectic phase surrounding Mg-alpha. X-rays diffractometry was performed on FSP samples to index phases and calculate peak shifts of Mg-alpha.
Friction Stir Welding of Line-Pipe Steels
Authors: Sanderson S. , Mahoney M. , Feng Zhi Li , Larsen S. , Steel R. , Fleck Dale
Published: May 2014

Friction stir welding (FSW) offers both economic and technical advantages over conventional fusion welding practices for welding line-pipe. For offshore line-pipe construction, the economic savings has been shown to be considerable, approaching a calculated 25%. Offshore pipe is relatively small diameter but heavy wall compared to onshore pipe. One concern is the ability to achieve consistent full weld penetration in an on-site offshore FSW operation, e.g., on a lay-barge. Further, depending on the size and morphology of the unwelded zone, lack of penetration at the weld root can be difficult if not impossible to detect by conventional NDE methods. Thus, an approach to assure consistent full penetration via process control is required for offshore line-pipe construction using FSW. For offshore construction, an internal structural mandrel can be used offering the opportunity to use a sacrificial anvil FSW approach. With this approach, a small volume of sacrificial material can be inserted into the structural anvil. The FSW tool penetrates into the sacrificial anvil, beyond the inner diameter of the pipe wall, thus assuring full penetration. The sacrificial material is subsequently removed from the pipe inner wall. In the work presented herein, FSW studies were completed on both 6 mm and 12 mm wall thickness line-pipe. Post-FSW evaluations including radiography, root-bend tests, and metallography demonstrated the merits of the sacrificial anvil approach to achieve consistent full penetration.
Comparative Performance of Three High-Strength Ni-Cr-Mo Alloys in Oilfield Simulated H2S Environment
Authors: Roy Indranil , Marya Manuel , Susnitzky David , Deng Hong Qi
Published: May 2014

Three Ni-Cr-Mo alloys with 140ksi minimum yield strength, namely 625Plus, 718, and 945X were tested in selected sour environments to evaluate and rank their environmentally-assisted cracking susceptibility. The testing revealed that none of the alloys, stressed to 90% of their actual yield point, cracked as a result of an agressive 30-day NACE level VII-modified environment (401 ± 9 oF, 500 psia H2S, 500 psia CO2 and 151,700 mg/liter chlorides). In a complementary attempt to rank the alloy cracking susceptiblity, quasi-static strain rate (SSR) tests per NACE TM0198-2004 were conducted in a modified H2S-saturated NACE TM0177 Solution A. Following a critical analysis of parameters such as time-to-failure (TTF), percentage reduction in ductility (%ε), percentage reduction of cross-sectional area (% RA) and fractomicrographs, 625Plus was confirmed to outperform its counterparts while some evidence of hydrogen embrittlement was found on 945X.
Properties of Indium Tin Oxide/Amorphous Alloys Bi-Layer Films as Transparent Electrodes
Authors: Lin H.K. , Cheng K.C. , Cho Ting Pin , Huang J.C.
Published: May 2014

The amorphous alloy films of ZrCu and AgMgAl, layers deposited by co-sputtering was utilized as the metallic layer in the bi-layer structure transparent conductive electrode of ZrCu/ITO and AgMgAl/ITO deposited on the PET substrate using magnetron sputtering at room temperature. In the transmittance performance, the 30 nm ITO/3 nm ZrCu and 30 nm ITO/15 nm AgMgAl films could show the optical transmittance of 73 % and 70% at visible light of 550 nm wavelength and maintain the stable transmittance of 70~75% from visible light to infrared region. Meanwhile, the 30 nm ITO/9 nm ZrCu and the 30 nm ITO/15 nm AgMgAl films could show the better sheet resistance of 136 Ω/sq. and 135 Ω/sq. respectively. In addition, compared with the ITO film, the current metallic glasses were utilized as the metallic layer in the bi-layer structure transparent conductive electrode showed the better bending properties. The relative change of resistivity is below 0.4, significantly lower than that of the commercial PET/ITO product. The ZCI would exhibit lower variation in resistance owing to short crack propagated in the amorphous alloy of ZrCu layer after 10000 cycles bending test.
Warm Rolling Technique for Amorphous Alloy Strip Produced by Ultrarapid Cooling-Thermal Spraying Based on Hydraulic-Stress-Induced Structural Relaxation
Authors: Kurahashi R. , Morimoto Toshiharu , Fukudome Y. , Ishiura S.
Published: May 2014

Amorphous alloys have many superior properties such as high tensile strength,anticorrosion and easy soft-magnetism, but few amorphous alloys have been used as final productsbecause they lack plasticity at room temperature. Thus, we have developed a new amorphous alloyrolling method. Although the amorphous alloy was brittle at room temperature, it has deformedplastically by semisolid rolling under hydraulic stress. After being subjected to ultrarapidcooling-thermal spraying, amorphous alloy strips were rolled with a ditch roll in the viscoelasticregion below the glass transition temperature. Using this rolling method, we successfully preformedstrips for use in fuel cell separator. This rolling technique is based on the principle of stress-inducedstructural relaxation under hydraulic stress.
Tuning of Soft Magnetic Properties in FeCo- and FeNi-Based Amorphous and Nanocrystalline Alloys by Thermal Processing in External Magnetic Field
Authors: Skorvanek Ivan , Marcin Jozef , Kováč Jozef , Švec Peter , Lupu Nicoleta , Chiriac Horia
Published: May 2014

Thermal processing of materials in external magnetic field is employed in order to produce a controllable uniaxial anisotropy and to tailor a domain structure in the series of soft magnetic FeCo-and FeNi-based amorphous/nanocrystalline alloys. Examples of our recent work on the utilization of both longitudinal and transverse magnetic field annealing for tuning the shape of hysteresis loops as well as the giant magnetoimpedance (GMI) characteristics are briefly presented. The beneficial effects of a heat treatment under magnetic field are discussed in terms of the improved application-oriented properties of these soft magnetic alloys.