bluuebunny/crossref_metadata_2025 huggingface dataset:
Nucleation Rate and Number of Precipitates in V and Nb-Microalloyed Steels
Authors: Medina Sebastián F. , Gómez Manuel
Published: May 2014

Recrystallization-precipitation-time-temperature (RPTT) diagrams were experimentally determined for two microalloyed steels with V and Nb, respectively, at a strain of 0.35 and a strain rate of 3.63 s-1. From the RPTT diagrams, and applying the classic theory of nucleation, the nucleation rate was calculated for both steels. In order to determine the mentioned magnitudes, several parameters were calculated, such as: the Zeldovich factor (Z), the energy of formation of the nucleus (ΔG), the driving force for precipitation (ΔGv), the critical radius for nucleation (Rc), and the dislocation density at the start of precipitation (ρ), among others. The calculated data has made it possible to clarify the shape of precipitation start and finish curves and to plot the nucleation rate as a function of temperature. The number of precipitates was calculated by integration of the nucleation rate expression. In this way, substantial differences were established between the two types of microalloyed steels, including the final size of the V(C, N) and Nb (C, N) precipitates.
Microstructure, Fracture and Mechanical Properties of ECAPed Aluminum P/M Alloy with Respect to the Porosity
Authors: Bidulská Jana , Bidulský Robert , Grande Marco Actis
Published: May 2014

The main aim of this paper is to investigate the effects of different processing conditions on the behavior of a P/M (Powder Metallurgy) aluminum alloy with respect to the microstructure, fracture and mechanical properties. Moreover, the evolution of porosity as a consequence of pressing, sintering and ECAPing processes was investigated. A commercial Al-Mg-Si-Cu-Fe powder was used as material to be investigated. Different compacting pressures (400, 500, 600, 700 MPa) were applied. Specimens were dewaxed in a ventilated furnace at 400 °C for 60 min before sintering. Sintering was carried out in a vacuum furnace at 610 °C for 30 min. The specimens were ECAPed for 1 pass. The 2-dimensional quantitative image analysis was carried out by means of SEM and OM for the evaluation of the dimensional and morphological porosity characteristics. The detailed microstructure revealed the main features of sintering processes as well as secondary pores at the prior alloying particle sites. The tensile fracture surfaces in both studied processing condition (as-sintered and ECAP) show limited ductility, with fracture occurring on a plane normal to the tensile stress axis. Examination at higher magnifications revealed predominantly transparticle ductile features. In terms of mechanical properties, ECAP is almost doubling the tensile strength of the as-sintered materials
Creep Deformation of 10 mol% La2O3 + YSZ Ceramic Composite Prepared by Spark Plasma Sintering
Authors: Robles-Arellano Karen D. , Bichler Lukas
Published: May 2014

Development of creep-resistant 8mol% Yttria-stabilized Zirconia (YSZ) ceramic has received much interest due to its potential use in fuel cells and thermal barrier coatings. In this research, Spark Plasma Sintering was used to develop a high-density 10 mol% La203 + YSZ composite. Compressive creep testing was performed at 1300 oC at 45 – 78 MPa load. The mechanism of plastic deformation of the composite was studied using Scanning Electron Microscopy and X-Ray Diffraction. The results suggest that lattice diffusion and grain boundary sliding were the active creep mechanisms.
Effects of Geometric Constraint on Solidification Microstructural Development of Peritectic TiAl Alloys
Authors: Zhang S. , Krane M.J.M. , Johnson David R.
Published: May 2014

Directional solidification of binary peritectic TiAl alloys through preforms with straight channels with spacing on the order of the dendritic tip radius were simulated using a modified solid-liquid interface tracking model. Interruption of the steady-state growth of the primary β-phase by constraint of solutal diffusion within very thin sections of ceramic preforms can lead to solidification conditions favorable for the nucleation and continued growth of the peritectic α-phase even after the growth front has exited the preform.
Feasibility of Cast and Wrought Co-Al-W-X Gamma-Prime Superalloys
Authors: McDevitt Erin T.
Published: May 2014

In 2006, J. Sato et al. discovered the L12 gamma-prime phase in the Co-Al-W alloy system. Since that time there has been a significant academic effort to characterize and understand the thermodynamics, the structure, and properties of alloys in this system. That work has shown that such alloys have promise as next generation high temperature materials due to the ability to engineer a high gamma-prime content alloy with a higher gamma prime solvus and higher melting point than many Ni-base gamma-prime strengthened alloys. Furthermore, a relatively narrow range of solidification temperature and large range of temperature between the gamma-prime solvus and the solidus are two characteristics that suggest cast and wrought versions of the alloys should be able to be manufactured routinely. However, to date all published research has been on small, laboratory scale samples typically less than about 2 kg, cast and hot rolled or cast as single crystals.
This paper describes ATI’s experience in assessing the feasibility of manufacturing a cast and wrought billet product in the Co-Al-W-X alloy system. Three 22 kg heats were produced to examine a small range of alloy compositions of potential commercial interest: Co-9Al-9W, Co-9Al-9W-2Ti, and Co-9Al-9W-2Ti-0.02B, respectively. Each heat was vacuum induction melted and vacuum arc remelted. The as-cast microstructure will be presented. Ingots were homogenized and hot worked. The microstructure at various stages of production are shown and hot working behavior is described.
Mechanical Behaviors of Alloy 617 with Varied Strain Rates at High Temperatures
Authors: Calmunger Mattias , Chai Guo Cai , Johansson Sten , Moverare Johan
Published: May 2014

Nickel base alloys due to their high performances have been widely used in biomass and coal fired power plants. They can undertake plastic deformation with different strain rates such as those typically seen during creep and fatigue at elevated temperatures. In this study, the mechanical behaviors of Alloy 617 with strain rates from 10-2/s down to 10-6/s at temperatures of 650°C and 700°C have been studied using tensile tests. Furthermore, the microstructures have been investigated using electron backscatter detection and electron channeling contrast imaging. At relatively high strain rate, the alloy shows higher fracture strains at these temperatures. The microstructure investigation shows that it is caused by twinning induced plasticity due to DSA. The fracture strain reaches the highest value at a strain rate of 10-4/s and then it decreases dramatically. At strain rate of 10-6/s, the fracture strain at high temperature is now smaller than that at room temperature, and the strength also decreases with further decreasing strain rate. Dynamic recrystallization can also be observed usually combined with crack initiation and propagation. This is a new type of observation and the mechanisms involved are discussed.
Damage and Fracture Mechanism of a Nickel-Based Single Crystal Superalloy during Creep at Moderate Temperature
Authors: Tian Su Gui , Guo Zhong Ge , Shu De Long , Xie Jun
Published: May 2014

By means of creep properties measurement and microstructure observation, an investigation has been made into the damage and fracture mechanism of a nickel-based single crystal superalloy during creep at moderate temperature. Results show that the deformation mechanism of the alloy in the latter stage of creep is that the primary-secondary slipping systems are alternately activated, and the micro-crack is firstly initiated on the γ′/γ phases interface in the intersection regions of two slip systems. As creep goes on, the micro-crack is propagated along the γ′/γ interface, which is perpendicular to stress axis, to form the square-like cleavage plane on the (001) plane. Thereinto, the propagation of the cracks on (001) plane is intersected with {111} cleavage plane which is secondly activated, which may terminate the propagation of the crack to form the cleavage plane with square-like feature on (001) plane along the <110> directions. Due to the multi-cracks may be propagated on different cross-section of the alloy during creep, and the tearing edge or secondary cleavage plane are formed along the direction with bigger shearing stress at the crack tip, which makes the multi-cracks connected each other until the occurrence of creep fracture, this is thought to be the main reason of the creep fracture having the uneven and multi-level cleavage characteristics.
Mechanical Performance and Biocompatibility of Biomedical Beta-Type Titanium Alloy Subjected to Micro-Shot Peening
Authors: Akahori Toshikazu , Oguchi Yurie , Hattori Tomokazu , Fukui Hisao , Niinomi Mitsuo
Published: May 2014

Beta-type Ti-29Nb-13Ta-4.6Zr (TNTZ) was recently developed as a representative biomedical Ti alloy. As-solutionized TNTZ has a low Young’s modulus less than 60 GPa close to that of cortical bone along with very low cytotoxicity and good bone biocompatibility. Solution treatment and aging (STA) is a typical heat treatment for improving the mechanical properties of beta-type titanium alloys. However, STA also drastically increases the Young’s modulus. Therefore, this study investigated the effects of surface modification, micro-shot peening, on the mechanical properties of TNTZ subjected to severe thermomechanical treatment in order to maintain a relatively low Young’s modulus. The bone contact characteristics of TNTZ samples subjected to surface modification and cancellous bone were also compared. The Vickers hardness of cold-swaged TNTZ (TNTZSW) subjected to micro-shot peening was significantly increased within 20 mm from the very edge of the specimen surface. The fatigue strength of TNTZSW subjected to micro-shot peening increased especially in the high cycle fatigue life region. The fatigue limit was around 400 MPa. The bone formations on TNTZSW subjected to micro-shot peening and TNTZSW with the mirror surface as comparison material were almost identical to each other. However, the relative bone contact ratio of TNTZSW subjected to micro-shot peening was better than that of TNTZSW with the mirror surface.
Fatigue Behavior of 51 Vol.% Porous Ti-6Al-4V Alloy
Authors: Aşık Emin Erkan , Tunca Bensu , Nakaş Gül Ipek , Bor Şakir
Published: May 2014

Porous titanium alloys are widely used as implant materials due to their mechanical behavior similar to that of bone. In addition, fatigue properties of implant materials are especially important since medical implants mostly exposed to cyclic compressive loading conditions. In this study, porous Ti-6Al-4V alloy has been produced via sintering at 12000C for 2 hours employing magnesium space holder technique. Porosity of the produced foams were measured according to Archimedes’ principle and calculated to be in the range of 51 ± 1 vol.%. Mechanical properties of the foams were characterized by monotonic compressive and compression-compression mode fatigue tests. The compressive strength and elastic modulus of the foams were determined to be 167 ± 18 MPa and 12 ± 1 GPa respectively. Fatigue tests conducted with a frequency of 5 Hz and a constant stress ratio (σmin/σmax) of 0.1 revealed that porous Ti-6Al-4V alloys have a fatigue limit of approximately 135 MPa. Furthermore fracture surfaces of the foams were characterized by field emission scanning electron microscopy (FESEM).
3D Printing of Meso-Decorated Gels and Foods
Authors: Gong Jin , Shitara Mariko , Serizawa Ryo , Makino Masato , Kabir M. Hasnat , Furukawa Hidemitsu
Published: May 2014

Two kinds of 3D printers were developed in our group. One is bathtub-type gel printer named SWIM-ER. The other is ink-jet-type food printer named E-CHEF NO.1. Using Meso-Decorated gels and agar, 3D printing of the soft materials was carried out. The valve of blood vessel, which is difficult to build by soft materials, is printed successfully by SWIM-ER. Their dimensions became almost the same as the designed. We also succeeded in printing food by E-CHEF NO.1, while a few bubbles are found in the sample.
Oriented Collagen Scaffolds for Anisotropic Bone Tissue Construction In Vitro
Authors: Matsugaki Aira , Ozasa Ryosuke , Isobe Yoshihiro , Saku Taro , Nakano Takayoshi
Published: May 2014

Constructing biomimetic tissue architecture in vitro holds the key to the realization of tissue engineering. To control the anisotropic microstructure of bone tissue which governs the mechanical properties of bone, especially, is imperative for the establishment of ideal bone regeneration process. In this study, highly aligned collagen scaffolds were fabricated to control osteoblast alignment. Collagen fibrillogenesis were regulated by an extrusion process, resulting in formation of biomimetic, hierarchically-aligned bony microstructure. Osteoblasts adhered to the fabricated scaffolds showed aligned morphology along the collagen orientation. In the present method, the degree of scaffold orientation is regulatable, which suggests that the designing of the appropriate scaffolds depending on the tissue anisotropy is possible. Interestingly, the bone matrix produced by the aligned osteoblasts exhibited anisotropic microstructure along the cell alignment. Our findings imply that controlling the osteoblast alignment by oriented collagen scaffolds could be an initiator to establish the anisotropic bone structural development or regeneration.
Geometrical Micropillars Combined with Chemical Surface Modifications – Independency of Actin Filament Spatial Distribution in Primary Osteoblasts
Authors: Nebe J. Barbara , Finke Birgit , Koertge Andreas , Rebl Henrike , Staehlke Susanne
Published: May 2014

Cell-biomaterial interactions are strongly affected by topographical and chemical surface characteristics. We found out earlier that geometric titanium (Ti) pillar structures in the micrometer range induce the cells to rearrange their actin cytoskeleton in short fibers solely on the top of the pillars. As a result, cell physiology was hampered concerning collagen I synthesis and spreading capacity. Furthermore, the position-dependent initial cell adhesion strength was declined near the edges.
We asked whether these observed cellular effects can be performed only in combination with Ti or occur independently of chemical surface features. In addition, the specific culture conditions, e.g. serum content or influence of gravity, were of interest.
Human primary osteoblasts were cultured in Osteoblast Growth Medium with serum containing SupplementMix on pure silicon pillars (5x5x5 μm) or on samples additionally sputtered with Ti (as reference) or gold. To offer the cells ligands for their adhesion receptors, we coated the pillars with collagen I or alternatively with a plasma polymer layer from allylamine. Different from standard culture conditions, the cells were cultured against gravity as well as without serum. The actin cytoskeleton was stained with phalloidin-TRITC after 24 h and analyzed by confocal laser scanning microscopy. Interestingly, on all modifications tested the cell’s actin cytoskeleton was distinctly organized in short fibers on the top of the pillars. Thus, we were able to exclude the influence of (i) the material chemistry (gold, silicon, physical plasma vs. Ti), (ii) the protein deposition on the pillar top and edges, and (iii) the impression caused by gravity.
Alloy Design for Semi Solid Metal Forming
Authors: Govender Gonasagren , Möller Heinrich , Curle Ulyate Andries
Published: May 2014

Semi-solid metal forming is more than 40 years old but its full potential to near net shape form high strength aluminium alloys has been realised only to a limited degree. Alloys developed for traditional manufacturing processes were initially used but it became apparent that alloys specific to SSM forming needed to be developed. The main alloy development criteria revolved around SSM processing temperature, solid fraction (fs) versus temperature sensitivity and age hardening potential. This methodology while sound does not fully address the unique processing behaviour of SSM forming. By its very nature SSM requires the controlled solidification of a part of the melt before forming. From basic solidification fundamentals this results in the enrichment of the remaining liquid with alloying elements. During the forming process segregation of liquid phase essentially produces a component with very different compositions in the regions where the liquid solidifies last. From recent work completed on a wide range of standard alloy systems it has become apparent that this segregation effect has a significant impact on aging behaviour and strength. Low melting point structures formed in the these regions result in localised melting in the grain boundary region and along areas of gross liquid segregation during solution heat treatment, contributing to the poor mechanical properties. Although this behaviour can be addressed using modified heat treatment, this cannot be applied to all current alloy systems. Alloy design for SSM forming must take these phenomena into account in order to develop and or specify aluminium alloys with acceptable mechanical properties.
Biocompatibility of Titanium Dioxide Film Modified by Femtosecond Laser Irradiation
Authors: Tsukamoto Masahiro , Shinonaga Togo , Nagai Akiko , Yamashita Kimihiro , Hanawa Takao , Matsushita Nobuhiro , Xie Guo Qiang , Abe Nobuyuki
Published: May 2014

Titanium (Ti) is one of the most widely used for biomaterials, because of its excellent anti-corrosion and high mechanical properties. In addion to these properies, the bioactivity of Ti is required. Recently, coating of the titanium dioxide (TiO2) film on Ti plate surface is useful methods to obtain biocompatibility of Ti plate. If periodic nanostructures were formed on the film surface, direction of cell spreading might be controlled due to grooves direction. Then, femtosecond laser is one of the useful tools of periodic nanostructures formation. Peiriod of periodic nanostructures might be varied by changing the laser wavelength. In the experiments, the film was formed on Ti plate with an aerosol beam which was composed of submicron size TiO2 particles and helium gas. The film was irradiated with the femtosecond laser. Laser wavelengths of the laser was at 1044, 775 and 388 nm, respectively. Periodic nanostructures, lying perpendicular to the laser electric field polarization vector, were formed on the film by femtosecond laser irradiation at 1044, 775 and 388 nm, respectively. The period of the periodic nanostructures on the film produced by femtosecond laser irradiation at 1044, 775 and 388 nm was about 350, 230 and 130 nm, respectively. In the cell test, cell spreading along the grooves of the periodic nanostructures was observed although it was not done for the film without the periodic nanostructures. These results suggested that direction of cell spreading could be controlled by the periodic nanostructures formation
Substrate Independent Approach for Immobilisation of Quaternary Ammonium Compounds to Surfaces to Reduce Bio-Burden
Authors: Cavallaro Alex , Majewski Peter , Barton Mary , Vasilev Krasimir
Published: May 2014

Bacterial contamination of biomedical devices is an ongoing problem. One method to alleviate such contamination is the introduction of surface compounds onto devices which can kill bacteria on contact. Polymers containing quaternary ammonium groups are known for their antimicrobial properties. Here we report a substrate-independent two-step method for the immobilisation of quaternary ammonium groups onto any type of surface. To achieve this glycidlytrimethylammonium chloride was covalently bound to plasma polymerised allylmine interlayer. Changes in the membrane permeability of Escherichia coliwere observed by BacLight LIVE\DEAD staining. 30% of E. coli grown on the treated surfaces showed high levels of membrane permeability within 4 hours. Importantly, there was no observable cytotoxic effect on human dermal fibroblasts.
Plasma Modification of DLC Films and the Resulting Surface Biocompatibility
Authors: Wang Mei , Zhao Ying , Xu Rui Zhen , Zhang Ming , Fu Ricky K.Y. , Chu Paul K.
Published: May 2014

Diamond-like carbon (DLC) films were synthesized on a p-type silicon wafer using radio-frequency plasma composed of a mixture of Ar and C2H2 (ratio of 7 to 28). NH3 plasma treatment of as-grown DLC substrate was carried out to generate surface-terminal amino groups while oxidation of as-grown DLC was performed in O2 plasma. X-ray photoelectron spectroscopy (XPS) was used to characterize the different surface functions formed on DLC surfaces. Water contact angle measurements indicate different wetbility of modified surfaces. The cell (Mouse MC3T3-E1 pre-osteoblasts) morphology and proliferation were monitored to evaluate the biocompatibility of the modified DLC surfaces. A cell count kit-8 (CCK-8 Beyotime) was employed to determine quantitatively the viable pre-osteoblasts. The cell viability assay shows that osteoblast proliferation are improved on NH3 and O2 plasma-treated DLC surface after culturing for 1day, 2days and 3 days. The cell-surface interactions are studied by fluorescence microscopy. There are more osteoblasts as well as better spreading on the aminated and oxidized surfaces after culturing for 3 days. In summary, compared to the as-grown sample, the modified DLC shows better biocompatibility.
Formation of Fe-Al Intermetallic Compound Film on High-Speed Tool Steel by Shot Lining and Heat Treatment
Authors: Harada Yasunori , Ishida Makoto , Takahashi Katsuhiko
Published: May 2014

Shot peening is widely utilized to improve the fatigue property of mechanical parts for transportation equipment such as cars and airplanes. Also, this technology is being applied as a film-forming technology in order to improve surface quality. The authors have recently proposed new joining methods using shot peening, shot lining. In this method, the metals are bonded with the dissimilar metal by applying plastic deformation and the pressure. The thin foil can be joined to the substrate surface by the pressure generated by the hit of the shots. In this study, the formation of an Fe-Al intermetallic compound film on high-speed tool steel by shot lining and heat treatment was investigated. In the experiment, a centrifugal-type peening machine with an electrical heater was employed. The shot medium was high-carbon cast steel. The substrate was a commercial high-speed tool steel JIS-SKH51, and the foil was commercially available pure aluminium. The shot lining process of tool steel with an aluminium foil was carried out at 573K in air using a peening machine. Heat treatment was performed at diffusion temperatures from 923 to 1573K in vacuum. The lined substrates exhibited a harder layer of aluminium-rich intermetallics in the diffusion temperature range of 923 to 1173K. When the temperature of the lined substrates was more than 1273K, the surface was covered with thicker and highly anticorrosive layers of iron-rich intermetallics. We found that the present method could be used for the formation of functional films on high-speed tool steel.
Influence of SiO2 Nanoparticle Codeposition on Homogeneity of Zinc-Nickel Alloy Plating from an Acid Sulphate Bath
Authors: Hino Makoto , Murakami Koji , Muraoka Ken , Nagata Norihito , Kanadani Teruto
Published: May 2014

Zinc-nickel-SiO2 electrodeposits have been produced from an acid sulphate bath. Thecodeposition behavior of SiO2 and the homogeneity of platings were examined. The presence ofSiO2 nanoparticles in the plating bath appears to change the alloy deposition behavior. Rate ofnickel deposition was considerably decreased with SiO2 nanoparticles in the bath. The homogeneityof platings between zinc and nickel were improved by adding the SiO2 nanoparticles in the bath. Atan early stage of electrodeposition, it seems that the SiO2 nanoparticle acts as a nucleus of theprecipitation. The SiO2 nanoparticle has not uniformly dispersed in a plating film, but distributedonly in the SiO2 rich layer with about 50 nm in thickness formed beneath the surface. In addition,this SiO2 rich layer can improve the anticorrosive performance. Therefore, the zincic use can besuppressed, because film thickness can be more thinned, compared with zinc and zinc-nickel alloyelectroplating.
Mechanical and Structural Properties of Superhard TiAlSiN Coatings Deposited by Arc Ion Plating of Cylindrical Cathode
Authors: Kim Wang Ryeol , Kwon Min Chul , Lee Jung Hoon , Jung Uoo Chang , Chung Won Sub
Published: May 2014

TiAlSiN coatings were deposited on WC-Co metal by using a cathodic arc ion deposition method of cylindrical cathode. We used Ti / Al (50 / 50 at.%) arc target and silicon sputter target. The influence of the nitrogen pressure, TiAl cathode arc current, bias voltage, and deposition temperature on the mechanical and the structural properties of the films were investigated. The structural features of the films were investigation in detail using X-ray diffraction. And coatings were characterized by means of FE-SEM, nanoindentation, Scratch tester, Tribology tester, XRD and XPS. The hardness of the film reached 43 GPa at the cathode arc current of 230 A and decreased with a further increase of the arc current. And the adhesion of the film reached 34 N. The results showed that the TiAlSiN coating exhibited an excellent mechanical properties which application for tools and molds.
Role of Sn on the Adhesion between Cu-Sn Alloy Coated Steel and SBR Based Rubber
Authors: Banerjee Atanu , Dutta Monojit , Bhowmick Anil K. , Laha Tapas
Published: May 2014

The effect of Cu-Sn coating on steel towards improving the adhesion between steel and typical styrene butadiene rubber (SBR) based tyre bead composition has been investigated in this work. Steel coupons were coated with varying compositions of Cu-Sn via immersion coating, where the electrolyte bath composition was varied. Chemical analysis of the coatings using ICP-OES confirmed increase in Sn content with increasing SnSO4 concentration in the coating baths, keeping other parameters constant. No change in the coating weight was observed with change in Sn concentration in the coatings. Bare spots on the coating surface was observed under SEM XPS analysis confirmed formation of Fe oxide at the bare locations. The coated steel plates were vulcanized with SBR based rubber and peel strength was measured. The results confirmed an optimum Sn concentration of 3 - 4 wt% in the coatings up to which an increase (~ 25%) in adhesion strength was exhibited compared to only Cu coatings. Stereo-microscopic analysis of the peel tested samples validated mixed mode i.e. both adhesive and cohesive modes of failure.
A Novel Process for Grain Refining and Semisolid Processing
Authors: Wang Xiang , Zhao Tong , Tie Di , Guan Ren Guo
Published: May 2014

A novel process for grain refining and manufacture of high quality semisolid slurries ofalloys was developed. The process was proven to refine metal grain remarkably, and the grain sizeof pure aluminum can be refined to the first grade of Chinese refining standard of pure aluminumGB/T 7946.4-1999 ref) . P rimary silicon and eutectic silicon in the hypereutectic Al-Si alloy can bealso effectively refined. This process was used to prepare the billets with small spherical grains orequiaxed grains of Al-6Si-2Mg, AZ91, AZ31 and hypereutectic Al-Si alloys successfully. The p ip es ,profi le s and wire s of 6201, AZ31 and AZ61 alloys were produced by continuous rheo-extrusion.The strips of AZ91, AZ31, and Mg-Sn alloys were prepared by rheo-rolling. As an innovativeprocessing technology with low cost and high efficiency, vibrating sloping plate melt treatment hasgood prospective application in many fields such as rheo-casting, rheo-extrusion, rheo-rolling,metal microstructure refinement, etc.
Deposition of Self-Assembled Monolayer on Vanadate Conversion Coated AZ31 Mg Alloy
Authors: Salman S.A. , Akira N. , Kuroda Kensuke , Okido Masazumi
Published: May 2014

Self-assembled monolayer (SAM) was adsorbed on the surface of vanadate conversion coated AZ31 magnesium alloy. The SAM thin film was deposited using (Tridecafluoro-1, 1, 2, 2-tetrahydrooctyl) trimethoxysilane (FAS13) and Tetrakis (trimethylsiloxy) titanium as a catalyst. Contact angles measurement, SEM, XRD, EDS and XPS were employed to analyze the surface morphologies, molecular composition, phase structure and wettability of the coatings formed on Mg alloy substrate. Corrosion resistance property of the coatings was also examined using the anodic polarization method and salt spray test. The anticorrosion property was improved with SAM post treatment. Furthermore, the contact angle increases from 12 deg. to 165 deg. indicating to production of super hydrophobic surface with SAM post treatment.
Effect of Yarn Structure on Mechanical Properties of Twisted Yarn Composites
Authors: Nakamura Rie , Goda Koichi
Published: May 2014

T
wisted yarns are used for bio-composites and nanocomposites
as
reinforcement
. In a twisted yarn, single yarns migrate from surface to inner along the yarn axis. In this
research
, migration structure is studied by
using X-ray CT
system
. The result is obtained that the orientation angle correlates with
layer
.
Processing-Property Relationships in Advanced Multi-Functional Composite Materials: Management of Dielectric Behavior
Authors: Reifsnider Kenneth , Rabbi Fazle , Baker Jeff , Adkins Jon Michael , Liu Q.
Published: May 2014

Many of the advanced composite materials used in aerospace, energy storage and conversion, and electrical devices are multifunctional, i.e., they operate on (or in the presence of) some combination of mechanical, thermal, electrical, chemical, and magnetic fields. Designing composite materials for airplanes, for example, must include not only structural, but also thermal and electrical considerations. Most energy storage and conversion devices are made from advanced composite materials, and they must be designed to interact and sustain their functions in multiple fields, often mechanical, electrical, electrochemical, and thermal. The functional characteristics of such materials are not only controlled by the constituent properties, but are highly dependent on the size, shape, geometry, arrangement, and interfaces between the constituent materials, the extrinsic factors controlled by processing. That is the subject of the present paper. In particular, we will focus on the design of microstructure in heterogeneous materials to manage the dielectric properties and character of such materials.
TEM and XRD Study of Nanostructured Composite Materials Reinforced with the Halloysite Particles
Authors: Dobrzański Leszek Adam , Tomiczek Błażej , Pawlyta Mirosława , Nuckowski Paweł
Published: May 2014

In the present work selected results of TEM and XRD investigations of the new AA-6061 matrix composite materials reinforced with halloysite nanoparticles manufactured by mechanical alloying and hot extrusion are present. Halloysite nanotubes, being a clayey mineral of volcanic origin which is characterized by high porosity, large specific surface, high ion exchange and easy chemical and mechanical treatment, can be used as alternative reinforcement of metal matrix composite materials. The composite materials obtained as a result of mechanical alloying and hot extrusion are characterized with the structure of evenly distributed, disperse mineral phase particles in fine-grain matrix of AA-6061 alloy, facilitate the obtainment of higher values of strength properties, compared to the initial alloy. Thanks to HRTEM analysis, the occurrence of grains sized ca. 20÷30nm in the composite materials reinforced with halloysite nanotubes with 15% mass share has been confirmed. The crystallite size and lattice strain of the obtained composites were calculated from X-ray line broadening, applying different profiles of diffraction lines. The achieved values of crystallite size for composites powders after 6 hours of milling were in the range 65-150nm, depending on the calculation method.
Thermal Properties of Porous Copper Manufactured by Lost Carbonate Sintering
Authors: Xiao Z. , Zhao Y.Y.
Published: May 2014

Active cooling techniques are often required to achieve high rates of heat dissipation in thermal management applications. Open-cell porous metals are good candidates for use as heat exchangers. This paper studies the fluid transport and thermal properties of porous copper samples with different pore structures manufactured using the LCS method. The results showed that the permeability increases with porosity but decreases with pore size. The thermal conductivity increases with relative density according to the power law. The effects of porosity and pore size on the heat transfer performance of the porous copper samples are significant, due to their effects on the permeability and thermal conductivity. For the porous copper samples with double-layer structures, the permeability follows the rule of mixture and the heat transfer coefficient can be predicted by a recently developed segment model.
Plasticity and Fracture of InP/Si Substructures
Authors: Le Bourhis Eric , Pantzas Konstantinos , Patriarche Gilles , Sagnes Isabelle , Troadec David , Talneau Anne
Published: May 2014

We report on the mechanical response of semiconductor substructures formed by InP membranes bonded to silicon. The bonded surfaces are of the order of ~ 1 cm2 and were bonded using oxide-free direct wafer bonding. Both the plastic response of the InP membrane and the InP/Si interface strength have been investigated using instrumented nanoindentation.
Phases Stability of Ni-Mn-Ga Alloys Studied by Ab Initio Calculations
Authors: Xu N. , Raulot J.M. , Li Z.B. , Zhang Y.D. , Bai J. , Peng W. , Zhao X. , Zuo Liang , Esling Claude
Published: May 2014

The phase stabilities and magnetic properties in Ni-Mn-Ga alloys are systematically investigated by means of the first-principles calculations within the framework of density functional theory using the vienna ab initio simulation package. The calculated formation energies show that the tetragonal NM martensite is the most stable phase compared with the cubic austenite and the modulated monoclinic martensite for stoichiometric Ni2MnGa. The atomic magnetic moment keeps constant in austenite and NM martensite, whereas those of Ni and Mn in the modulated martensite oscillate according to the atomic position. Furthermore, The formation energies of the various compositions have been systematically calculated.
Surface Modifications of TiO2 by Ion Implantation
Authors: Ionescu Mihail , Atanacio Armand , Davies Joel , Nowotny Janusz , Gregg Daniel , Vance Lou , Bak Ted
Published: May 2014

Rutile is a good candidate for total water oxidation and hydrogen production due mainly to its corrosion resistance in water. In its native form, the direct band gap of 3.02eV, with the absorption edge in the visible part of the solar spectrum at 416nm, but close to the UV region, results in poor photo-catalytic efficiency of around 3%, well below the commercial threshold of around 10%. One option to enhance the photo-catalytic efficiency is band gap engineering, through the reduction of the Fermi level, which may be achieve by either changing the oxygen activity, or the incorporation of aliovalent foreign ions. The incorporation of donor and acceptor-type of ions may lead to a shift in the Fermi level close to the conduction or valence bands. Single crystals of TiO2-Rutile (SG: P4 2/mnm), with (001) orientation were implanted along <001> at 10keV and 2MeV, where the range of C in TiO2 is 21nm and 1.6μm, respectively. The ion implantation was carried out at various equivalent C concentrations, and characterised in-situ by ERDA with 82MeV Iodine, and PIXE with 2.5MeV protons. Optic band gap was assessed by ground state band structure calculations based on CASTEP code, with geometry optimisation by general gradient approximation and PBE functional, and energy optimisation by local density approximation and CA-PZ functional.
Dynamic Observation of Hydrogen Gas Release during Crack Propagation in Al-Zn-Mg Alloy
Authors: Horikawa Keitaro , Hokazono Shunsuke , Kobayashi Hidetoshi
Published: May 2014

We have developed a new testing device, which is capable of detecting hydrogen gas evolution from the microstructural changes at the same timing. The device is composed of the tensile testing machine equipped with a high-speed microscope and two types of quadrupole mass spectrometers installed in the ultrahigh vacuum chamber. Sampling rate of microscopic observation is 2000 fps. Hydrogen or deuterium was pre-charged to the 7075 aluminum alloy by means of the slow strain rate deformation, together with the exposure under the humid air atmosphere. The hydrogen amount was measured by using a thermal desorption analysis in advance. As a result, it was revealed that hydrogen gas was evolved when the surface crack was generated around the notch root of the test specimen. SEM observation also showed that the initial crack is related to the propagation of grain boundary fracture around the notch root. When compared to the microstructure and the hydrogen gas evolution near the notch root, the hydrogen amount evolved at the grain boundary was estimated to be about 3.0×10-7 mol/m2.
Nafion – Azole Composite Membranes for High Temperature PEMFC
Authors: Kim Je Deok , Jun Mun Suk
Published: May 2014

Nafion-azole (benzimidazole, 1,2,4-triazole, 1,2,3-triazole) composite membranes were prepared by room temperature and autoclave solution processing for high temperature (above 100 °C) PEMFC. Among the various Nafion – azole composite membranes, Nafion – 1,2,3-triazole membrane showed excellent flexibility, thermal stability, and homogeneous structure. Nafion – 1,2,4-triazole composite membrane had high thermal and mechanical properties, and also showed high proton conductivity of 0.02 S/cm at the temperature of 160 °C under dry (N2) condition.
Effect of Gaseous Impurities on Degradation of SOFC Materials
Authors: Yamaji Katsuhiko
Published: May 2014

Fundamental studies on durability and reliability of SOFC modules/stacks had started as one of the new NEDO project from FY2005 and the organization had been partly modified at FY2008 and FY2013[1]. The main target is to make sure the long term durability within 10 % of degradation rate in the range of 40,000 h (5 years), and reliability during 250 times of starting up and ending operations. In this project, the effect of impurities on degradation of SOFCs was examined for 5 different stacks/modules (Kyocera, Tokyo gas, TOTO, MMC-KEPCO and MHI) at AIST. During the operation of SOFC stacks and modules, several kinds of impurities are carried continuously with air and fuels and react with cell components. The concentration of impurity in cell components was carefully investigated before and after long term operation by using a secondary ion mass spectrometer (SIMS) as a main analytical tool with conventional analytical techniques such as a scanning electron microscopy (SEM) and an electron probe micro analyzer (EPMA). Many approaches were carried out to investigate the effect of gaseous impurities as listed below. (1)The concentration of impurity in cell components was carefully investigated before and after long term operation. (2)Chemical reactivity between impurities and cell components are examined from the view point of thermodynamics. (3)In order to understand the mechanism of the degradation due to impurities, the effect of impurities on degradation of laboratory scale button cell were examined. (4)Cation diffusion were carefully investigated in some diffusion couples to clear the mechanism on formation of secondary phases between the cathode and electrolyte. (5)Acceleration tests on degradation by impurities were also carried out by using a button cell to predict the degradation rate depending on the contamination of impurities in the cathode. The results of the project is partly introduced in this report.
Isothermal and Non-Isothermal Annealing of Cold-Rolled Al-Mn-Fe-Si Alloys with Different Microchemistry States
Authors: Huang Ke , Li Yan Jun , Marthinsen Knut
Published: May 2014

Investigation of the microstructural evolution of Al-Mn-Fe-Si alloys during annealing after cold rolling has been carried out. The effect of microchemistry state in terms of Mn in solid solution, constituents, size and volume fraction of dispersoids, introduced prior to cold rolling through different homogenization treatments, on microstructural evolution is compared during subsequent isothermal and non-isothermal heating experiments, with focus on the dependency of the amount solute (potential for concurrent precipitation) and pre-existing particles prior to deformation. It is clearly demonstrated that the actual kinetics and final microstructure are the result of a delicate balance between processing conditions and microchemistry state. In general, non-isothermal annealing treatments produce inhomogeneous microstructure, as compared to isothermal annealing. Moreover, more and finer particles (resulting from low-temperature homogenization) tend to hinder boundary motion, leading to even slower recrystallization kinetics and coarse non-equiaxed grains with a strong P texture component.
Influence of Galvanized Coatings on Abrasion Circle Friction Stir Spot Welding Aluminium to Steel for Automotive Applications
Authors: Chen Ying Chun , Liu Si Fang , Prangnell Phil B.
Published: May 2014

It has previously been shown that dissimilar Al-alloy and un-coated steel automotive sheets can be successfully welded with a cycle time of less < 1 s using a novel solid state joining approach; Abrasion Circle Friction Stir Spot Welding (ABC-FSSW). The ABC-FSSW technique provides an effective strategy for exposing a larger clean steel surface during welding than conventional FSSW, allowing high failure energy joints to be produced. In this study the influence of different steel zinc coatings on the viability of the ABC-FSSW process has been systematically investigated - focusing on the effect on the process window, weld temperatures, and joint performance. The effect of a galvanised coating on the weld formation, zinc dispersal in the joint, and interface intermetallic reaction behaviour are discussed.
Challenges in Joining Aluminium with Copper for Applications in Electro Mobility
Authors: Kaspar Joerg , Zimmermann M. , Ostwaldt A. , Goebel G. , Standfuß J. , Brenner B.
Published: May 2014

The effective joining of aluminium with copper is one of the central technical goals involved in electro mobility. However, the joining of both metals by conventional fusion welding is challenging because of poor weldability arising from different chemical, mechanical and thermal properties of the materials and especially from the massive formation of hard and brittle intermetallic compounds (IMC) weld interface. In order to accomplish the difficult task of joining aluminium and copper several new joining technologies and strategies such as Laser Beam Welding (LBW) using highly dynamic beam deflection, Friction Stir Welding (FSW), Laser Induction Roll Plating (LIRP) and Electromagnetic Pulse Welding (EMPW) are under development at the Fraunhofer IWS. The current work describes the different technological approaches to the dissimilar joining of aluminium and copper. Thereby, the different joining technologies are compared with respect to weld quality. Special consideration is given to the study of interface morphology and microstructure of the welding zone. It will be shown that, depending on the joining method chosen the kind and extension of intermetallic phase formation differs considerably. Conclusions are drawn with respect to the applicability of the different joining methods.
Numerical Simulation Model for FSW Employing Particle Method – Effect of Tool Angle on Fluid Motion
Authors: Miyasaka Fumikazu , Yoshikawa Gaku , Matsuzawa Shuhei
Published: May 2014

The friction stir welding (FSW) is known as non-melting joining. It used widely in the field of industry. Numerical analysis models for FSW also have been developed. In these models, the most frequently used method is a grid method (finite element method or finite difference method). However it is difficult or troublesome to calculate the advective term both for momentum and temperature employing these methods. It is also difficult to calculate the big deformation of the material's free surface. Moreover, complex process is required to analyze the dissimilar joining with respect to dealing with substance transfer. In this paper, to avoid these difficulties, particle method is adopted for FSW simulation. In particle method, advective term, substance transfer, and surface deformation are calculated automatically mainly because that Lagrangian approach is used. To verify the effectiveness of this method, fluid motion around the tool is examined by particle trace. As a result, relations between the rotating speed of the tool and area of plastic flow is evaluated.
Assessment of the Advantages of Static Shoulder FSW for Joining Aluminium Aerospace Alloys
Authors: Wu Hao , Chen Ying Chun , Strong David , Prangnell Phil B.
Published: May 2014

Stationary (or Static) Shoulder Friction Stir Welding (SS-FSW) is a variant of FSW that was developed primarily to improve the weldability of titanium alloys by reducing the through thickness temperature gradient. Surprisingly, SS-FSW has been largely ignored by the Al welding community because it is widely supposed a rotating shoulder is an essential aspect of the process and that the higher conductivity means the surface heating effect of the shoulder is generally beneficial. In the work presented it is shown that SS-FSW has major advantages when welding high strength aluminium alloys; including a reduction in the heat input, a massive improvement in surface quality, and a narrower and more symmetric temperature distribution, which leads to narrower welds with a reduced heat affected zone width and lower distortion. The reasons for these benefits are discussed based on a systematic study aimed at directly comparing both processes.
The Influence of Gaps and Misalignment on Friction Stir Welded Butt Joints of Medium-Sized Parts
Authors: Schulze Sebastian , Göbel G. , Richter-Trummer V. , Füssel U. , Beyer Eckhard
Published: May 2014

In order to industrialize friction stir welding (FSW) processes, not only the machine concept itself needs to be evaluated, but also the robustness of the process application being carried out on the machine. Especially for FSW of medium-sized and larger parts, a small degree of misalignment can have an increasing influence on the weld quality. Therefore an exemplary tolerance study for friction stir welded butt joints was conducted. The intentional introduction of gaps between the sheets to be welded can limit the welding process and thus the weld quality. However, for the considered experimental set-up it can be shown that the introduction of a well-defined gap can support the welding process and weld quality.
The experimental procedure was carried out on a parallel kinematic machine - a so-called Pentapod. This machine is suitable for large and complex three-dimensional structures. Although the machine is able to record the process forces (Fx, Fy and Fz) acting on the tool–work piece interface, the forces acting perpendicular to the clamping system are still unknown. Therefore additional load cells were integrated into the clamping system to measure the in-process reaction forces. The combined results of the force measurements give a nearly complete overview of the internal loads during the process. In conjunction with knowledge about gaps and misalignment, the data gained in this study can help to understand and predict the clamping behaviour, and thus design rules for future clamping systems can be derived.