bluuebunny/crossref_metadata_2025 huggingface dataset:
Controlling Silver Ion Release from Ag-Based Nanocoatings by Plasma Surface Engineering
Authors: Bonilla-Gameros Linda , Cloutier Maxime , Montaño-Machado Vanessa , Chevallier Pascale , Mantovani Diego
Published: December 2018

Environmental surfaces have been widely recognized as an important source of hospital-associated transmissions. A number of silver-based antibacterial coatings have been reported in the literature. However, the success of any antibacterial strategy depends on the ability to control the kinetics of the silver ions released from the coating. The novel strategy proposed in this work is based on plasma surface engineering for a controlled-release of silver ions. Plasma-based nanocoatings, plasma oxidation processes and surface patterning of silver coatings were designed and optimized. Surface analyses such as XPS and AFM, as well as silver ion release over 168 h, was evaluated by MIP-AES. Results showed that surface plasma engineering successfully allow tuning the silver release and bioactivity in Ag-containing antibacterial coatings.
Dry Surface Preparation Using Supercritical Cryogenic Nitrogen Jet Improves the Adhesion Strength of Cold Gas Sprayed Coatings (SCNCS)
Authors: Tazibt Abdel , Ezo'o Guillaume , Khalsi Yosri , Yahiaoui Mustapha
Published: December 2018

The adhesion performance of Cold Sprayed coatings depends on the quality of the substrate [1,2,4,8]. Before deposition, the surface of substrate must be prepared to a specific required quality, which promotes the anchoring of sprayed coating. Grit Blasting (Samson et al.) [1] is known as the conventional surface preparation before Cold Spraying. But such method causes issues: a) shallow roughness, which does not strengthen bonds between layer and substrate; b) embedment of particles in the substrate, which creates discontinuity of the material at the interface and causes cracks that degrade the layer. Recently, Laser [2] and Pulsed Water Jet (PWJ) [1] have been tested as substrate preparation methods. These methods have shown their ability to generate improved roughness without particle embedment. PWJ has particularly shown interest in Al substrate to generate crevices, which are anchors for the Cold Sprayed coatings. Nevertheless, Laser affects thermally the substrate and induces constraints that may disadvantage the coating quality. PWJ generates liquid effluents. Besides some substrates such as ferrous metals can react with oxygen of water leading to corrosion and coating adhesion weakness.
Au-Ni and Rh Electroplated Coatings Evaluation for ITER Ion Cyclotron Resonance Heating Radio-Frequency Sliding Contacts
Authors: Chen Zhao Xi , Hillairet Julien , Turq Viviane , Song Yun Tao , Laloo Raphaël , Yang Qing Xi , Vulliez Karl , Lombard Gilles , Bernard Jean Michel , Hernandez Caroline , Mollard Patrick , Volpe Robert , Ferlay Fabien
Published: December 2018

Within the large scale fusion experimental device ITER, Ion Cyclotron Resonance Heating (ICRH) system is one of the three heating systems which will supply total heating power of 20 MW (40-55 MHz) up to one hour operation. Radio-Frequency (RF) contacts are integrated within the antennas for assembly and operation considerations, which will face extremely harsh service conditions, including neutron irradiation, heavy electrical loads (RF current reaches up to 2 kA with a linear current density of 4.8 kA/m), high thermal loads and also long-duration vacuum baking at 250°C before each experimental plasma campaign. CuCrZr and 316L steel have been shown to be proper base candidate materials for ITER RF contact louvers and conductors respectively. However, in order to limit the wear and the diffusion phenomena at the RF contact as well as to reduce the contact resistance, functional protective layers should be developed. The aim of this work is to investigate Au-Ni and Rh functional layers, electroplated on CuCrZr and 316L respectively. The efficiency of the Au-Ni/Rh coated pairs was evaluated through thermal ageing diffusion tests, using EDS cross-section mapping and XRD techniques. Wear and electrical contact performances of the Au-Ni/Rh original and thermally aged pairs have also been deeply studied on a dedicated tribometer operated at ITER relevant conditions.
The Effect of Potential on Surface Characteristic and Corrosion Resistance of Commercial Pure Titanium Processed by Anodic Oxidation Treatment
Authors: Fu Tian Lin , Liu Shan , Gao Yan , Zhan Zhao Lin
Published: December 2018

Anodic oxidation treatment of commercial pure titanium was carried out at the voltage of 30, 50 V in 0.5 M H2SO4 solution so as to obtain the effects of the anodic potential on the surface characteristic and corrosion resistance of passive film. The morphology and corrosion resistance of the treated samples were investigated using scanning electron microscopy (SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization curves and electrode impedance spectroscopy (EIS). The results show that increasing anodic potential can significantly enhance the corrosion resistance of commercial pure titanium.
Mechanical Fields on Cross-Shaped Specimens for Stress Corrosion Cracking of Cold-Worked Austenitic Stainless Steels
Authors: Huang Qi , Charles Yann , Duhamel Cécilie , Gasperini Monique , Crepin Jérôme
Published: December 2018

The aim of this work is to better understand the evolution of the mechanical fields in cross-shaped specimens used to study the stress corrosion cracking (SCC) susceptibility of cold-worked stainless steels exposed to the primary water of nuclear power plants. Cross-shaped specimens are used since a loading path change leads to more severe cracking than a monotonous loading. During SCC tests, only the applied load and displacement can be measured as a result of experimental equipment limitations. Therefore, a mechanical test is performed ex-situ under similar condition as the ones applied during the SCC tests. The experimental deformation fields are measured by digital image correlation (DIC) and a numerical model is developed with ABAQUS to calculate the mechanical fields. The obtained results will allow us to calibrate SCC tests already performed but also to know the experimental boundary conditions to apply to reach a given strain value during forthcoming SCC tests.
The Influence of Ni Content on the Corrosion Resistance of Cu-Ni-Sn-C-P Sintered Alloys in Poor Quality Fuel
Authors: Sunada Satoshi , Mizukoshi Yusuke , Sakagami Riku , Takezoe Shinichi , Ishii Yoshinari , Nunomura Norio , Hatakeyama Masahiko
Published: December 2018

The copper alloys, which were added Nickel show high corrosion resistance. Therefore, they are generally used in environments of poor quality fuel. However, it is expected that we reduce the amount of Ni in copper alloy, due to increase of Nickel consumption in recent years. We used five different types of sintered material samples that are different in the content of Nickel in the present study, to investigate the influence of Ni content to corrosion resistance quantitatively. These samples were used for the experiment of open circuit potentials, anodic and cathodic polarization curves measurements. To simulate environment in poor quality fuel we employed solution of 0.5 M Na2S + 0.1 M NaOH (pH = 13.05). The experiment of open circuit potentials shows that samples that the content of Nickel is less than 42 mass% were formed passivation film on surface of sample during aeration. The experiment of polarization curves measurements show that the each sample was implied behavior of forming passivation film corresponding to potential-pH diagram of Cu in anodic region basically. In addition, the 36.4 mass% Nickel was remarkably improved corrosion resistance.
Relationship between Microstructure and Exfoliation Corrosion in Mg-14mass%Li-3mass%Al Cold-Rolled Alloy
Authors: Obata Yutaro , Morishige Taiki , Goto Takayuki , Nakamura Eiji , Takenaka Toshihide
Published: December 2018

Relationship between microstructure and exfoliation corrosion in Mg-14mass%Li-3mass%Al cold rolled material were investigated by controlling microstructure using heat treatment. The exfoliation corrosion was exhibited on the specimens with elongated microstructure by cold-rolling. Heat treatment at 200 C only recovery occurred. Recovery and recrystallization were caused by heat treatment at 300 C However, heat treated at 300 C decreased precipitate fraction. Corrosion rate of heat-treated at 200 C decreased by release the residual strain. However, heat treatment at 300 C has lower corrosion resistance than heat-treated at 200 C because it has less precipitate density than as-rolled. Exfoliation corrosion was shown in as-rolled and heat-treated at 200 C. In as-rolled exfoliation corrosion was shown more significant when reduction rate increase. In as-rolled, exfoliation corrosion was shown more significant than heat-treated at 200 C. After heat treatment to change the grain shape from elongated to equiatial, exfoliation was suppressed by the distribution of AlLi phase.
Cleaning Optimization of Hot-Dip Galvanized Steel Surfaces in Preparation for Paint Application
Authors: Schoeman Liezl , Burty Marc
Published: December 2018

Hot-dip galvanized steel surfaces are cleaned, pre-treated with titanium-containing solution and then painted for use. Removal of the alumina layer from galvanized steel surfaces during the cleaning process is essential before effective paint application. Bad adhesion results if the alumina layer is not completely removed, and an insufficient concentration and uneven distribution of titanium oxide is formed across the galvanized surface during pre-treatment. The alkaline cleaner concentration must be optimized to ensure effective removal of the alumina layer. Hot-dip galvanized steel samples were cleaned using typical line conditions and cleaning solutions with varying free alkalinities. The alumina layer was then measured on each sample by glow-discharge optical emission spectroscopy. Thereafter, the samples were treated with titanium-containing pre-treatment solution. The titanium oxide concentration was measured by inductively coupled plasma optical emission spectroscopy. It was found that a free alkalinity of at least 3.2 mEq/L is required to fully remove the alumina layer. The alumina-free samples also gave a titanium oxide layer after pre-treatment within the target concentration of 4–8 mg/cm2. A free alkalinity of 3.5 ml was thereafter implemented commercially: analysis of samples from two galvanizing lines showed no presence of alumina, a uniform titanium oxide distribution across the widths of the line samples and acceptable titanium concentrations.
Simple Fabrication of Superhydrophobic Surfaces Using Atmospheric-Pressure Plasma
Authors: Vazirinasab Elham , Jafari Reza , Momen Gelareh , Carreira Tony
Published: December 2018

Nature-inspired superhydrophobic surfaces have received immense industrial and academic interest due to their non-wettability and self-cleaning properties. To fabricate superhydrophobic silicone rubber surfaces, a simple, environmentally friendly atmospheric-pressure plasma treatment was applied. The effect of diverse plasma processing parameters on the final wettability behavior of the substrates, including plasma power, plasma frequency, number of passes, plasma jet speed, plasma cycle time and distance between the nuzzle outlet and substrate, were analyzed by means of design of experiments (DoE). Surface chemical characterization illustrated the influence of plasma treatment on the chemical composition of the produced silicone rubber. Furthermore, the presence of microstructures as well as the chemical composition of the surface was confirmed using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy analysis.
Understanding Cold Spray for Enhanced Manufacturing Sustainability
Authors: Widener Christian A. , Ellingsen Marius , Carter Michael
Published: December 2018

High pressure cold spray has been showing increasing promise and application for structural repairs and coating applications where wrought like strengths are required. For example, numerous applications have been developed for repairing high cost and long lead time parts for the aerospace and defense market, such as aircraft skin panels, titanium hydraulic lines, aluminum valve actuator internal bores, hardened and chromed steel shafts, gas turbine engine parts, magnesium castings, and many more. These processes also have direct application in commercial markets like transportation and heavy industry. In particular, parts with lead times in excess of 12 months have been successfully repaired and re-introduced into service. This saves not only the direct cost of the part, but also returns the system to service much sooner. Additional benefits of field application with a hand-held nozzle assembly are also possible, particularly for power plants, refineries, and other large industrial plant operations. Cold spray consequently has a tremendous opportunity to enhance manufacturing sustainability by repairing parts that previously could only be replaced and recycled. It is environmentally friendly, as there are no toxic fumes or other harmful emissions from cold spray. Furthermore, because parts are being repaired and refurbished rather than replaced, there is tremendous cost, energy, and overall environmental benefit, making cold spray a “green” technology and an excellent technology for enhancing the long-term sustainability of high value assets.
Superhydrophobic Coating Bioinspired on Rice Leaf: A First Attempt to Enhance Erosion Resistance Properties at Environmental Conditions with Ceramic Particles
Authors: Rius-Ayra Oriol , Castellote-Alvarez Roger , Escobar Ana M. , Llorca-Isern Nuria
Published: December 2018

This study develops a new, facile and rapid process bioinspired on rice leaf with the aim of producing a hybrid composite coating in a first attempt to obtain a superhydrophobic coating with enhanced erosion resistance properties. Rice leaves (Oryza sativa L.) are made of hierarchical structures consisting of micropapillae and waxy nanobumps which confer to the surface a contact angle of 164° as Lotus leaf does. In particular, rice leaves accumulate amorphous silica inside and on the surface with various morphologies. This kind of silica is produced by absorbing silicates from the soil under specific conditions of temperature and pressure. The presence of biosilica in rice leaves is useful for preventing diseases or improves mechanical properties of the leaves. Single-step and two-step processes are the two strategies applied for generating a superhydrophobic coating by electrochemical deposition of ZnCl2, α-Al2O3 and lauric acid (C11H23COOH) onto commercial pure aluminum substrate. The static contact angle measured on the coating gives values of 170° and 1° for the sliding angle conducing to a coating with superhydrophobic and self-cleaning properties. Various characterization techniques are used to determine chemical and morphological structure such as FESEM, XPS or FTIR. On one hand, in morphological analysis, flower-like structure is obtained with petals thickness of 70nm corresponding to the nanostructured contribution to the system. On the other hand, chemical analysis concludes the generation of zinc laurate (Zn (C11H23COO)2) as a major compound contributing to the reduction of surface tension and increasing the superhydrophobic character of the coating as well.
Mass Transfer in Yb Silicate Environmental Barrier Coatings at High Temperatures
Authors: Kitaoka Satoshi , Matsudaira Tsuneaki , Wada Masashi , Kawashima Naoki , Yokoe Daisaku , Takata Masasuke
Published: December 2018

The oxygen permeabilities of polycrystalline Yb2Si2O7 wafers cut from sintered bodies to serve as models of environmental barrier coatings were determined at temperatures up to 1673 K under various oxygen potential gradients (dµO), produced by exposing the upper and lower surfaces of the wafer to atmospheres with different oxygen partial pressures (PO2). Oxygen permeation proceeded via grain boundary (GB) diffusion of oxygen from the higher PO2 surface to the lower PO2 surface, concurrently with GB diffusion of ytterbium in the opposite direction. Mass transfer analysis allowed for a design guideline for selectively enhancing the structural stability of the ytterbium silicate layer with applying a dµO.
Development and Properties of Cast TiAl Matrix In Situ Composites Reinforced with Carbide Particles
Authors: Lapin Juraj , Klimová Alena , Štamborská Michaela , Kamyshnykova Kateryna , Pelachová Tatiana
Published: December 2018

The In Situ composites with microstructurally different types of intermetallic matrix such as nearly γ (TiAl) (composite A), multiphase with high amount of lamellar α2(Ti3Al) + γ (TiAl) regions (composite B) and fully lamellar α2 + γ (composite C) were prepared by centrifugal casting and consecutive heat treatments of Ti-44.5Al-8Nb-0.8Mo-3.6C-0.1B, Ti-37Al-7Nb-0.8Mo-5.9C-0.1B and Ti-46.4Al-5Nb-1C-0.2B (at.%) alloys, respectively. The centrifugal casting results in a uniform distribution of coarse primary carbide particles in the as-cast samples. Hot isostatic pressing (HIP) and heat treatments have no effect on the Vickers hardness of the in-situ composite B but lead to a significant softening of the in-situ composites A and C. The in-situ composite C with a coarse-grained fully lamellar matrix shows a higher flow stress at 1000 °C and improved creep resistance at 800 °C compared to those of the in-situ composites A and B.
Elaboration of Architectured Copper Clad Aluminium Composites by a Multi-Step Drawing Process
Authors: Moisy Florent , Gueydan Antoine , Sauvage Xavier , Keller Clément , Guillet Alain , Nguyen Nga , Martinez Mayerling , Hug Eric
Published: December 2018

Architectured copper clad aluminium composites processed by a restacking drawing method at room temperature are reported in this work. Wires were drawn to severe plastic strain without any intermediate annealing. Three different diameters were studied in order to examine the influence of a different plastic deformation level on the structure of the different wires. Thanks to image processing it has been shown that independently of the plastic deformation, inserted fibers remain continuous and are homogeneous in size and shape. Furthermore, XRD and TEM characterizations confirm that there is no significant intermetallic growth during the deformation. Thus, the improvement and/or degradation of the functional properties of the wires can be well controlled by performing an appropriate post-processing annealing treatment. Keywords: Cu/Al composite, architectured wire, drawing, microscopy, image processing
On the Study of a TiB2 Nanoparticle Reinforced 7075Al Composite with High Tensile Strength and Unprecedented Ductility
Authors: Ma Yu , Ji Gang , Chen Zhe , Addad Ahmed , Ji Vincent
Published: December 2018

Strength and ductility are the two most important mechanical properties of a structural material. However, they are often mutually exclusive. In this study, a 6 wt. % TiB2 nanoparticle reinforced 7075Al (i.e. TiB2/7075Al) composite was designed and produced by the processing route combining casting, friction stir processing, hot extrusion and T6 heat treatment. The result of tensile testing demonstrates that the as-processed composite sample presents an ultimate tensile strength of 677 MPa and a total elongation to failure of around 15 %, being higher than any Al or Al based materials ever reported. The typical microstructure contains the TiB2 reinforcement nanoparticles uniformly distributed in the equiaxed Al grain matrix (2 μm in average grain size). In addition to the dispersed nanoprecipitates of the 7075Al (Al-Zn-Mg-Cu) matrix, the integrated TiB2 nanoparticles are systematically decorated by a shell corresponding to (Zn1.5Cu0.5)Mg. This finding challenges our understanding and opens a door for further enhancing strength and ductility being easily scalable for industrial applications.
Tensile Fracture of TiB Whisker Reinforced Ti Alloy Matrix Composites
Authors: Kurita Hiroki , Kondoh Katsuyoshi , Umeda Junko , Yodoshi Noriharu
Published: December 2018

TiB whisker reinforced Ti alloy matrix (Ti–TiB) composites have attracted attention as the aerospace materials with their high specific mechanical properties for long time. However, strengthening mechanism of Ti–TiB composites has not been revealed because of the agglomeration and incomplete precipitation of TiB whiskers in the Ti alloy matrix yet. In this study, we addressed to fabricate fully-dense TiB whisker reinforced Ti-6Al-4V alloy matrix (Ti6Al4V–TiB) composites via powder metallurgical process, which have the microstructure to discuss their tensile properties with the theories for composite materials. The Young’s modulus and ultimate tensile strength of Ti6Al4V–10 vol% TiB composite were 130 GPa and 1193 MPa, respectively. Note that the elongation of Ti6Al4V–10 vol% TiB composite was approximately 2.8 % although the elongations of Ti–TiB composite have been reported are few (; less than 1%) due to the agglomeration of TiB whiskers in Ti matrix.
Structural Stability of Hafnia-Based Materials at Ultra-High Temperature
Authors: Sévin Louise , Julian-Jankowiak Aurélie , Justin Jean François , Langlade Cécile , Bertrand Pierre , Pelletier Nicolas
Published: December 2018

This study assesses the structural stability at ultra-high temperature of the following selected compositions: 6.5 and 14 mol. % of RE2O3 (RE = Dy, Y, Er, Yb, and Lu) doped HfO2. Under thermal cycling and thermal shock, the structural stability was evaluated at 2400°C with water vapor flux using a specific test bench with a 3 kW CO2 laser. The cubic phase stability, which is theoretically important in the broad temperature range from 25 to 2800°C, was determined by a quantitative analysis of the X-ray diffractograms. Fully and partially stabilized HfO2, obtained respectively with 14 mol. % and 6.5 mol. % of dopants, showed different behaviors to thermal damage. Thermal expansion was measured up to 1650°C to anticipate dimensional changes of these stabilized samples and to be able to design an optimized material solution fitting with future combustion chamber requirements. All of these results were then considered in order to exhibit a trend on the thermal stability at 2400°C of the ionic radius of the dopants and their optimal doping rates.
Understanding Hot vs. Cold Rolled Medium Manganese Steel Deformation Behavior Using In Situ Microscopic Digital Image Correlation
Authors: Dutta Aniruddha , Ponge Dirk , Sandlöbes Stefanie , Raabe Dierk
Published: December 2018

We address the differences in yield stresses between hot and cold rolled medium manganese steel showing continuous yielding. Continuous yielding in both, the hot and cold rolled samples were resulting from reverted austenite islands plastically deforming first and less strain in the tempered martensite matrix. At higher global strains, strain was taken up not only by the reverted austenite, but also by tempered martensite and fresh martensite formed from the austenite through martensitic phase transformation during deformation. Strain localization was also observed in the hot rolled samples. This localization is caused by cumulative deformation of colonies of lamellar reverted austenite islands. It is interpreted in terms of the spatial alignment of austenite colonies to the loading direction in addition to the crystallographic orientation.
Multilayer and Fiber Metal Laminate Materials Hydro-Bulging
Authors: Sherkatghanad Ehsan , Lang Li Hui , Liu Shi Chen
Published: December 2018

Advanced materials such as aluminum alloys and composites offer great potential for weight reduction applications in automotive and aerospace vehicles construction. In order to investigate the feasibility of using such materials in the form of laminates, sheet bulging with single-layer aluminum and the aluminum/Composite laminate with the carbon cloth as the middle layer is investigated under uniform liquid pressure conditions. The aluminum sheet stress-strain, wall thickness distribution, carbon fiber radius stress-strain distribution and the effect of die entrance radius etc. are discussed and compared in details. FE results validate that the numerical method can predict the same fracture regions for bulging-blank as observed in experimental tests. Furthermore, the study validates that multi-layer sheet hydro-bulging process with composite fiber as a middle layer is not feasible to form laminates due to rupture of composite fibers near edge regions. Further study is needed to improve the methodology.
Rapid Synthesis of Li2O-(Nb/Ta)2O5-TiO2 Solid Solution Having Superstructure by Smart Processing Techniques
Authors: Nakano Hiromi
Published: December 2018

We successfully synthesized Li1+x-yM1-x-3yTix+4yO3 solid solutions (M = Nb or Ta, LMT, 0.07 ≤ x ≤ 0.33, 0 ≤ y ≤ 0.175) that have a superstructure. The materials formed a superstructure known as the M-phase, which is formed by the periodical insertion of an intergrowth layer in a matrix having a trigonal structure. The homogeneous and periodical structure of M-phase in LNT needed to sinter at 1393 K for 40 h-200 h using a conventional electric furnace. In order to form the homogeneous intergrowth layers rapidly, millimeter-wave or air-pressure control atmos furnaces were also used as smart processing techniques. We concluded that atomic diffusion was promoted in the useful reaction-fields: millimeter-wave radiation or high oxygen pressure.
Dislocation Densities in Dispersion-Strengthened Copper with Aluminum Oxide from X-Ray Line Profile Analysis
Authors: Sano Mutsumi , Takahashi Sunao , Watanabe Atsuo , Shiro Ayumi , Shobu Takahisa , Nakada Kenogo
Published: December 2018

Dislocation densities of dispersion-strengthened copper with aluminum oxide, namely GlidCop were evaluated employing the X-ray line profile analysis using the modified Williamson-Hall and modified Warren-Averbach method. X-ray diffraction profiles for GldCop samples with compressive strains applied at ambient temperature were measured with synchrotron radiation. The dislocation densities of GlidCop with compressive strain ranging from 0 – 2.7 % were on the order of 1.5×1014 – 6.6×1014 m-2.
Comparison of the Hot Working Behavior of Wrought, Selective Laser Melted and Electron Beam Melted Ti-6Al-4V
Authors: Bambach Markus , Sizova Irina , Geisen Ole , Fergani Omar
Published: December 2018

The production of high-temperature components is of great importance for the transport and energy sector. Forging of high-temperature alloys often requires expensive dies, multiple forming steps and leads to forged parts with large tolerances that require machining to create the final shape. Additive manufacturing (AM) offers the possibility to print the desired shapes directly as net-shape components. AM could provide the advantage of being more energy-efficient compared to forging if the energy contained in the machining scrap exceeds the energy needed for powder production and laser processing. However, the microstructure and performance of 3D-printed parts will not reach the level of forged material unless further processes such as hot-isostatic pressing are applied. Combining AM and metal forming could pave the way for new process chains with little material waste, reduced tooling costs and increased part performance. This study investigates the hot working properties and microstructure evolution of Ti–6Al–4V pre-forms made by selective laser melting and electron beam melting. The results show that both materials are hot workable in the as-built state. Due to its martensitic microstructure, the SLM material shows a lower activation energy for hot working than EBM and wrought material and a faster globularization during forming, which is beneficial for hot forming since it reduces the forming forces and tool loads.
Effect of Cooling Rate on Intermetallic Compounds Formation in Sn-Ag-Cu-In Solder
Authors: Miki Kenji , Kobayashi Tatsuya , Shohji Ikuo , Nakata Yusuke
Published: December 2018

The effect of the cooling rate in bonding on IMCs formation and their morphology in the solder joint with Sn-3.0Ag-0.7Cu-5.0In (mass%) lead-free solder was investigated. As the substrate, the Cu plate and the Cu plate with electroplated Ni were prepared. Bonding was conducted in the vacuum atmosphere, and bonding temperature and time were 300°C and 10 minutes, respectively. The cooling rates in the bonding were changed from 0.02°C/s to 0.2°C/s. In both Cu/Cu and Cu/Ni joints, scallop-shaped IMCs form at the joint interfaces regardless of the cooling rate. In the Cu/Cu joint, Cu6(Sn,In)5 and Cu3(Sn,In) layers form at the joint interface. In the Cu/Ni joint, (Cu,Ni)6(Sn,In)5 and (Cu,Ni)3(Sn,In) layers form at the joint interface with Cu and the (Cu,Ni)6(Sn,In)5 layer forms at the joint interface with Ni. Die shear force of the Cu/Ni joints are a little larger than those of the Cu/Cu joints. Fracture occurs in the boundary between the scallop-shaped layer or the granular IMC layer and the layered IMC in both joints. The cooling rate from the peak temperature to solidification is an important factor to decide the shape of formed IMC. When the cooling rate is high and supercooling becomes large, formation of pillar-shaped IMCs occurs easily.
Effects of Sputtering Pressure on (ZnO)x(InN)1-x Crystal Film Growth at 450°C
Authors: Itagaki Naho , Takeuchi Kazuto , Miyahara Nanoka , Imoto Kouki , Seo Hyun Woong , Koga Kazunori , Shiratani Masaharu
Published: December 2018

We studied effects of sputtering pressure on growth of (ZnO)x(InN)1-x crystal films deposited at 450°C by rf magnetron sputtering. Epitaxial growth of (ZnO)x(InN)1-x films was realized on single-crystalline ZnO template. X-ray diffraction measurements show that full width at half maximum of the rocking curves from the (101) plane of the films reaches minimum value of 0.11º at 0.5 Pa. The sputtering gas pressure is a key tuning knob for controlling the crystal quality of ZION films.
Differences in Morphologies of GaN-Based Nanocrystals Grown on Metal-Foils and Multi-Crystalline Si Substrates
Authors: Sato Yuichi , Fujiwara Atomu , Trung Nguyen Duc , Saito Sora
Published: December 2018

Gallium nitride (GaN)-based thin films consist of its nanocrystals are grown on some metal-foils and a multi-crystalline silicon (Si) substrates. Their morphologies are compared with each other and the differences are discussed. Pillar-shaped nanocrystals are observed in the film grown on the multi-crystalline Si substrate while such structures are not observed in the films grown on the metal-foils when they are grown at higher growth temperatures. On the other hand, the morphologies of the films grown on the metal-foils approach to pillar-like structures by reducing the growth temperature. Band-edge emission is clearly observed in a cathodoluminescence spectrum of the film grown on the metal-foil at the reduced growth temperature.
Crystal Plasticity Simulation Considering Microstructures of Austenitic Stainless Steel on Macroscopic Yield Function
Authors: Aoyagi Yoshiteru , Sagara Atsushi , Watanabe Chihiro , Kobayashi Masakazu , Todaka Yoshikazu , Miura Hiromi
Published: December 2018

In this study, yield surfaces of austenitic stainless steel produced by a cold-rolling process are measured using uniaxial and biaxial tensile tests. Using results obtained by electron backscatter diffraction, information on crystal orientation is introduced into a computational model for a multiscale crystal plasticity simulation. Finite element simulations for polycrystal of fine-grained austenitic stainless steel under biaxial tension are performed in order to predict yield surfaces of fine-grained austenitic stainless steel. Validity of predicted yield surfaces is evaluated by comparison between yield surfaces obtained by numerical simulations and experimental tensile tests.
One Photon 3D Polymerization via Direct Laser Writing
Authors: Mochi Federico , de Matteis Fabio , Prosposito Paolo , Burratti Luca , Francini Roberto , Casalboni Mauro
Published: December 2018

A way to produce 3D scaffold is via laser stereolithography. We propose a method of direct laser writing for micro-stereolithography in which we use as light source a low power blue diode laser with a wavelength of 448nm. The material chosen for scaffold fabrication is a polyethylene glycol diacrylate (PEGDA) solution at concentration of 75% in ethanol. We chose a short PEGDA molecule with a molecular weight of 575 g/mol, in order to obtain a better control over the polymerization. We used Irgacure 819 as photoinitiator to initiate the photopolymerization. The absorption of the Irgacure 819 almost drops to zero at the excitation wavelength, so the efficiency of the photopolymerization is strongly reduced. Since the intensity of the light reduces by a factor 5 within a penetration depth, equal to the depth of focus of the optical system, we achieve a fine control of the vertical and lateral photopolymerization of the solution. The threshold for effective polymerization is not reached outside that region.
Heat Treatment Behavior of the 18Ni300 Maraging Steel Additively Manufactured by Selective Laser Melting
Authors: Guo W.F. , Guo C. , Zhu Qiang
Published: December 2018

The steel 18Ni300 is widely used for tooling of injection moulding and die casting industries. Additive manufacturing (AM) technology is applicable to manufacture dies with “ideal” design without construction of manufacturing reality. Selective laser melting (SLM) processed materials have finer microstructure due to steeper temperature gradient and more rapid cooling conditions than conventional casting process during solidification. This difference may make different heat treatment behavior in obtaining optimal properties of the 18Ni300 maraging steel manufactured by SLM. Heat treatment is one of the most processes to improve microstructure, mechanical properties and performance of tooling dies. This work studies evolution of microstructure and properties during heat treatment, by X-ray diffraction, optical and scanning electron microscopy (SEM). The results show that the SLMed materials with only aging treatment have comparable strengths and hardness to those of conventionally cast materials with both solution and aging treatment. For the SLMed materials, with increase of aging time and/or temperature, the formed reverted austenite (γ-Fe) fraction increases, while aging precipitation hardening decreases. This is more apparent at aging temperatures of higher than 540°C. The combined effects of softening by formation of reverted austenite (γ-Fe) and age hardening induced by precipitation are discussed.
Direct Laser Additive Manufacturing of Ceramics by Powder Deposition
Authors: Odinot Julie , Julian-Jankowiak Aurélie , Petit Johan , Choron Damien , Boisselier Didier , Thomas Marc
Published: December 2018

In this study, LMD-CLAD® process (Direct Laser Additive manufacturing) is developed for alumina and Al2O3-Y2O3-ZrO2 ternary eutectic compositions. Powder flowability, laser-material interaction and thermal gradient control have been investigated. Powder granules of aforementioned compositions have been designed by spray-drying. Particle size distribution, Hall funnel test and SEM observations have been performed. Flowability has been improved by 20% in order to match with the LMD-CLAD® process by adjusting their density, size and surface quality. Otherwise, optical absorption of the ceramics has been increased up to 90% thanks to the addition of doping ions. With such a flowability improvement, laser powder deposition tests were successful and enabled us to investigate the effect of laser parameters and thermal environment on deposited beads state.
Developing New Materials for Electron Beam Melting: Experiences and Challenges
Authors: Koptyug Andrey , Bäckström Mikael , Botero Carlos , Popov Vladimir , Chudinova Ekaterina
Published: December 2018

Lack of industrially available materials for additive manufacturing (AM) of metallic materials along with the promises of materials with improved or unique properties provides a strong drive for developing new process/material combinations. As powder bed technologies for metallic materials are relatively new to the market, and to some extent are only maturing, developers of new process/material combinations have certain challenges to overcome. Firstly, basic knowledge on the behavior of materials (even those well established for other applications) under extreme conditions of melting/solidification with beam-based AM methods is far from being adequate. Secondly, manufacturing of the equipment is up to date driven by industrial application, thus optimization of the AM machines for small test batches of powders is still belongs to research and development projects. Also, majority of the powder manufacturers are primarily driven by the market development, and even they are well aware of the demands imposed by the powder bed AM machines, availability of small test batches of adequate powders may be problematic or at least quite costly for the R&D oriented users. Present paper describes the experiences in developing new materials for EBM A2 machine by Arcam EBM, modified for operating with powder batches of 100-200 ml and less. In particular it discusses achievements and challenges of working with powders from different materials with specifications far beyond the range suggested by machine manufacturer. Also it discusses the possibility of using blended rather than pre-alloyed powders for achieving both composite-like and alloyed materials in the same part by steering electron beam energy deposition strategy.
New Sustainable Hybrid Porous Materials for Air Particulate Matter Trapping
Authors: Bontempi Elza , Zanoletti Alessandra , Bilo Fabjola , Tushtev Kamen , Valente Gabriele , Zappa Dario , Treccani Laura , Depero Laura Eleonora
Published: December 2018

Particulate matter (PM) is the air pollutant which has the most severe impact on health. Currently, around 90% of the population of European cities for which PM data exist is exposed to levels exceeding World Health Organization (WHO) air quality guidelines levels. To improve air quality in cities, the challenge is to develop an innovative material solution that can reduce the concentration of PM in the air. In this presentation new porous hybrid materials produced from sodium alginate and some by-products (silica fume, wood ash), are presented. The material porosity is obtained by thermal decomposition of sodium bicarbonate, made at low temperature (70-80°C). The structural and morphological characterization made by XRD, and SEM shows that the materials are porous organic-inorganic hybrid. The mechanical performances of the obtained materials are also investigated. On the basis of embodied energy and carbon footprint of materials primary production, the sustainability of the new obtained materials is evaluated and quantified. The different materials compositions are evaluated and compared in terms of mechanical strength and sustainability. The air particulate matter adsorption characteristics of the material are investigated by a laboratory room, to evaluate its adsorption capacity. Finally the versatility of the new material is also demonstrated in term of their design possibilities: these materials can be direct foamed, extruded, and also 3D printed, with several application advantages.
A Numerical Thermal Analysis of the Heating Process of Large Size Forged Ingots
Authors: Arkhazloo Nima Bohlooli , Bazdidi-Tehrani Farzad , Morin Jean Benoit , Jahazi Mohammad
Published: December 2018

Simulation and analysis of thermal interactions during heat treatment is of great importance for accurate prediction of temperature evolution of work pieces and consequently controlling the final microstructure and mechanical properties of products. In the present study, a three-dimensional CFD model was employed to predict the heating process of large size forged ingots inside an industrial gas-fired heat treatment furnace. One-ninth section of a loaded furnace, including details such as fixing bars and high-momentum cup burners, was employed as the computational domain. The simulations were conducted using the ANSYS-FLUENT commercial CFD package. The k-ε, P-1 and Probability Density Function (PDF) in the non-premix combustion, as low computational cost numerical approaches were employed to simulate the turbulent fluid flow, thermal radiation, combustion and conjugate heat transfer inside the furnace. Temperature measurement at different locations of the forged ingot surfaces were used to validate the transient numerical simulations. Good agreement was obtained between the predictions of the CFD model and the experimental measurements, demonstrating the reliability of the proposed approach and application of the model for process optimization purposes. Detailed analysis of conjugate heat transfer together with the turbulent combustion showed that the temperature evolution of the product was significantly dependant on the furnace geometry and the severity of turbulent flow structures in the furnace.
Prediction of Steel Transformation Temperatures Using Thermodynamic Modeling and Design of Experiments (DOE)
Authors: Loucif Abdelhalim , Touazine Heithem , Jahazi Mohammad
Published: December 2018

This paper presents a methodology in order to predict A1, solidus and liquidus temperatures using a relatively simple approach. The proposed approach is based on the combined use of the thermodynamic software Thermo-Calc and the composite centered design of experiments (DOE) method. Four important alloying elements (C, Ni, Mn and Cr) were considered in the DOE. The impact of each alloying element on the transformation temperatures was determined and discussed. It was found that carbon has the most important impact on solidus and liquidus whereas Ni, Mn, and Cr have a significant impact on A1. The proposed models were generated using Analysis of Variance (ANOVA) method. A good agreement between experimental and predicted results was found with a maximum error of 1.1 % for transformation temperatures. Furthermore, the proposed models were validated using a large amount of experimental data published in the literature with a maximum error equal to 7.8 %.
Change in Yield Strength of Nb-Bearing Ultra-Low Carbon Steels by Temper-Rolling
Authors: Yang Ling Ling , Nakagaito Tatsuya , Funakawa Yoshimasa , Kojima Katsumi
Published: December 2018

Yield strength of low carbon mild steel decreases when temper-rolling is applied to release yield point elongation. Generally mobile dislocation used to be considered as the cause of the YS lowering. However from Bailey-Hirsch theory, strength should be higher with temper-rolling because of the increase of dislocation density. To newly explain the lowering yield strength by temper-rolling, standing at the point that a few ppm carbon change Hall-Petch coefficient , decrease in yield strength by temper-rolling is investigated using an ultra-low carbon steel. Yield strength of steel with the small amount of solute carbon increased after 2% temper-rolling and didn’t change after aging. On the other hand, yield strength of steel with the high amount of solute carbon decreased after 2% temper-rolling and increased again after aging. Despite solute carbon content, the Hall-Petch σ0 increased by dislocation strengthening of temper-rolling. Hall-Petch coefficient ky of low solute carbon steel remained at the low level even after temper-rolling or aging , however, that of high solute carbon steels significantly decreased after temper-rolling and increased again after aging. Yield strength reduction of the high solute carbon steel can be attributed to the decrease of ky.
Use of a Zener Approximation for Heat Transfer Analyses of Quasi One-Dimensional Welding Problems
Authors: Gould Jerry E.
Published: December 2018

Most welding methods in use today involve heating and subsequent cooling of the substrates for joining. Not surprisingly, understanding of associated thermal cycles implicit with the various processes has been a key facet of welding research. While the tools are available for sophisticated numerical solutions, much insight can be gained from simplified analytical approaches. A wide range of joining technologies in use today can be addressed by nominal one-dimensional heat transfer analyses. These include, for example, resistance spot, flash-butt, and linear friction welding. In addressing heat transfer problems, the mathematical constructs for heat transfer are analogous to those for mass (diffusion) transfer. Not surprisingly, one dimensional heat transfer problems can be greatly simplified by adapting the Zener approximation from mass transfer. The work described here employs the Zener approximation to address the direct spot welding of aluminum to steel. The Zener approximation is used to understand heat flow progressively from the steel into the aluminum and finally the copper electrodes. The results are used to understand weld morphology and implicit cooling behavior
Evaluation of a Characteristic Temperature in the Relaxation of Metallic Glass Forming Liquids
Authors: Aniya Masaru , Ikeda Masahiro
Published: December 2018

The high-temperature viscosity of metallic glass-forming liquids is investigated by using the Bond Strength-Coordination Number Fluctuation (BSCNF) model developed by the authors. For many glass-forming liquids, a salient change in the structural relaxation is observed above the melting point. The temperature dependence of the structural relaxation exhibits a deviation from an Arrhenius-like behavior, and upon cooling it transforms to a non-Arrhenius-like one. In the present study, we show that the BSCNF model describes well the high-temperature viscosity behaviors of metallic liquids. The analysis based on the BSCNF model also enables to extract a characteristic temperature at high temperature. The results of the present study show that such characteristic temperature can be a good indicator for the evaluation of the range of the transition from the Arrhenius-like to the non-Arrhenius-like relaxation behavior.
Metaheuristic Ab Initio Optimum Search for Doping Effects in Nanocarbons
Authors: Tsuruta Kenji , Mitani Keiichi , Al Asad Md. Abdullah , Nishina Yuta , Gotoh Kazuma , Ishikawa Atsushi
Published: December 2018

We have developed a combined approach of metaheuristic optimization algorithms (MOA), such as the genetic algorithm, with an ab-initio materials simulation engine. Concurrent run of the ab-initio calculations with each different parameter set selected by the MOA searches the optimum condition within a given input-parameter space. Using this methodology, the optimum dopant and its position/structure at a graphene edge are found to be a multiple N-atoms doping at graphitic sites, which predicts to lead to better charging/discharging performance when it is used as an anode material of Li-ion battery.
Microstructure, Texture and Mechanical Properties after Cold Working and Annealing in a Biomedical Ti-Nb-Ta Alloy
Authors: Acharya Srijan , Gupta Praveen , Chatterjee Kaushik , Suwas Satyam
Published: December 2018

β titanium alloys, comprising alloying elements such as Nb, Ta, Zr, are considered promising materials for use in orthopedic applications, as the lower elastic modulus of these alloys, reduces the chance of implant failure caused by stress shielding. The mechanical behavior of these alloys depend on the composition as well as the stability of the phases. In the present study, the effect of cold rolling and subsequent annealing on the microstructure, texture and mechanical behavior of a Ti-Nb-Ta-O alloy has been investigated. Structural characterization was done using x-ray diffraction (XRD) and optical microscopy. Mechanical properties were evaluated by estimation of hardness and elastic modulus. The results show that, (1) the alloy contains single-phase β microstructure in both deformed as well as annealed condition with no evidence of deformation induced phase transformation, (2) the microstructures of cold worked alloy become increasingly inhomogeneous with dominance of shear bands at higher rolling strains, (3) high value of hardness to modulus ratio could be obtained in the present alloy due to stability of β phase and interstitial strengthening.