bluuebunny/crossref_metadata_2025 huggingface dataset:
Photolithography of 3D Scaffolds for Artificial Tissue
Authors: Prosposito Paolo , Melino Sonia , Ciocci Matteo , Francini Roberto , Mochi Federico , de Matteis Fabio , di Nardo Paolo , Ksenzov Slava , Schrader Sigurd , Casalboni Mauro
Published: November 2016

The present study is focused on the design and fabrication of novel functional 3D-hydrogel scaffolds for regenerative medicine. In order to critically analyzing the effect of the microarchitecture of 3D scaffolds for driving the cellular fate and diffusion of progenitor stem cells we have fabricate a number of scaffolds with different geometry, stiffness and composition. The physical characteristics of the scaffold determine indeed, as well the biochemical factors, the fate of the cells. We use an innovative composite material consisting of hydrogel with different molecular weight and with suitable accordion-like and woodpile structures in order to tailor stiffness and elasticity conferred to the final structure.These novel 3D bioinspired scaffolds were obtained by both single- (1PP) and two-photon polymerization (2PP) processing. In particular, 2PP scaffolds represent a great advantage with respect to previous achievements based on traditional methods. 3D-structures were fabricated with lateral resolution of some microns, allowing an advanced control of pore microarchitecture of defined tensile strength, and the inclusion of albumin microspheres with various functionalities. The morphological, biochemical and functional characteristics are discussed. Moreover, the effects of the structured hydrogel scaffolds on the proliferation and differentiation of adult stem cells is analyzed in view of the fabrication of portion of contractile cardiac muscle to be obtained In Vitro.
Fatigue Deformation Behavior of Fe-Mn-C-(Al) TWIP Steels
Authors: Guo Peng Cheng , Liu Shuai , Ma Peng Hui , Meng Jiang Ying , Zhang Fu Cheng , Qian Li He
Published: November 2016

The effects of Al on the monotonic deformation behavior of Fe-Mn-C twinning-induced plasticity (TWIP) steels have been extensively investigated; however, how the addition of Al affects the fatigue properties of these steels is unknown. The present paper deals with the cyclic deformation properties of Fe-22Mn-0.6C-0Al and Fe-22Mn-0.6C-3Al steels by means of total strain-controlled low-cycle fatigue tests. The total strain amplitude ranges from 0.002 to 0.01. The evolved microstructures of fatigued samples were observed by transmission electron microscopy. Results show that the addition of Al has a significant effect on the cyclic deformation behavior, fatigue lifetime and evolved microstructure of Fe-Mn-C TWIP steel.
A Statistical Methodology to Reconstruct Nucleation Pathways in the Fe-Cu System
Authors: Qin Lin , Redermeier Alice , Kozeschnik Ernst , Karner Carina , Dellago Christoph
Published: November 2016

In precipitation strengthened ferritic alloys, the Fe-Cu binary system is a well-studied model system. Still, many unsettled questions remain about the early stages of bcc Cu precipitation, most of which refer to the shape and composition of the critical and post-critical nuclei. Since the critical nucleation states are hard to investigate by experimental methods, we propose a computational strategy to reconstruct precipitation pathways and identify the nucleation states making use of Monte Carlo simulations combined with Rare Event Sampling methods. The precipitation process is reproduced by Monte Carlo simulations with an energy description based on the Local Chemical Environment approach, applying efficient pair potentials, which are dependent on the chemical environment, and the Forward Flux Sampling technique. This method provides profound insight into the shape and composition of the early-stage precipitates and also the critical cluster size and shape in dependency of the temperature and supersaturation.
Neutron Diffraction Analysis of Light Alloys: A Review
Authors: Lombardi A. , Vandersluis E. , Sediako D. , Ravindran C.
Published: November 2016

The development and application of low density alloys, such as Al and Mg alloys, has rapidly increased in the automotive sector in recent years. This necessitates advanced characterization techniques to assess the evolution of microstructure and phases during casting and processing. Further, understanding the mechanism of evolution of the defects is important in ensuring their minimization. Neutron diffraction has provided a method to determine the factors that trigger hot tearing in Al and Mg alloys as well as determining factors compromising integrity of powertrain components. In addition, neutron diffraction has been applied to examine the phase evolution during solidification of Al and Mg alloys enabling a better understanding of the effect of inoculants and solute additions on the solidification characteristics, resulting in improved castability. This paper highlights the frontiers of neutron diffraction analysis undertaken by the Centre for Near-Net-Shape Processing of Materials, Ryerson University and the CNL-Canadian Neutron Beam Centre.
Effect of Previous Grain Size on Recystallization Texture and the Formability of the Nb Ferritic Stainless Steel
Authors: Rodrigues Daniella Gomes , Alcântara Cláudio Moreira , Santos Dagoberto Brandão , de Oliveira Tarcísio Reis , Gonzalez Berenice Mendonça
Published: November 2016

The ferritic stainless steels are materials used in several segments due to the excellent combination of mechanical properties and corrosion resistance. The mechanical properties of these alloys are strongly dependent on the microstructural characteristics and crystallography texture. The aim of this experimental study is to investigate the roles of the grain size of the hot rolled sample on the development of the microstructure, texture and formability of ferritic stainless steel. The main elements of chemical composition of the steel under investigation were 16.0 %Cr, 0.021 %C, 0.024 %N and 0.35 %Nb. Coarse and fine grains samples were cold rolled up to 90% thickness reduction and annealed at 880°C with soaking time of the 24 s. The texture measurements were performed by Electron Backscattered Diffraction (EBSD) in the longitudinal section. The formability was evaluated by the R-value and planar anisotropy (Δr) in tensile tests. The final microstructure after annealed was more homogenous for smaller initial grain size sample. This condition was favorable to develop γ-fiber, with sharpness intensity in 111121 components. The highest R-value and smallest planar anisotropy was obtained for a {111}/{001} ratio around 5.37. On the other hand, coarser initial grain size sample had showed a heterogeneous microstructure and texture, performing badly in mechanical tests (anisotropy).
Age Hardening Behavior of Al-Li Alloys Produced by Sand Mold Process
Authors: Saikawa Seiji , Otsubo Chiharu , Ikeno Susumu , Komai Koichi
Published: November 2016

Al-Li alloys have higher mechanical properties and more lightweight than other conventional aluminum alloys. Therefore , it is focused as a good material for weight reduction of industrial fields. However, since the Al-Li alloy are highly active and hard to cast, there has been limited research on casting. In this study, age-hardening behavior of Al-2.5mass%Li alloys cast into sand and metal mold were investigated. All alloys cast into Y-block shape sand mold, and then artificial aged after solution treated at 743K for 36ks. Because of difference in quantity of precipitation by metastable δ’(Al3Li) phase, peak hardness of metal mold casting is higher than that of sand molds castings.
Shape Recovery of Polymeric Matrix Composites by Irradiation
Authors: Santo Loredana , Bellisario Denise , Quadrini Fabrizio
Published: November 2016

Shape memory composite (SMC) structures are of great interest for the aerospace applications. In previous works, the authors have studied SMC lab-scale deploying prototypes manufactured by using two carbon fiber composite layers with a shape memory polymer interlayer. The prototypes were produced in an initial configuration and subsequently it was changed in the memorizing step. The initial configuration was then recovered by heating. Memorization and recovery phases were performed by means of conventional heating (by hot air gun or heater plate). In this work, for the first time the authors evaluate the SMC heating by means of radiating lamps. A square plate was purposely produced and recovered after different memory steps. Time, temperature and recovery are measured during and after the tests. The radiating lamp power and type, and the distance of the SMC from the lamp are fundamental parameters for the heating phase. As result of the irradiation tests, the initial configuration can be successfully recovered without failures. This study is especially aimed to future space applications in which the deployment (recovery) phase will be initiated only by exposure to solar radiation.
Comparison of Microstructure and Mechanical Behavior of the Ferritic Stainless Steels ASTM 430 Stabilized with Niobium and ASTM 439 Stabilized with Niobium and Titanium
Authors: Tanure Leandro Paulo de Almeida Reis , de Alcântara Cláudio Moreira , de Oliveira Tarcísio Reis , Santos Dagoberto Brandão , Gonzalez Berenice Mendonça
Published: November 2016

The use of Ferritic Stainless Steels has become indispensable due its lower cost and the possibility to replace austenitic stainless steels in many applications. In this study, cold rolled sheets of two stabilized ferritic stainless steels with 85% thickness reduction were annealed by applying a heating rate of 24 oC/s and a soaking time of 24 s. The niobium stabilized ferritic stainless steel type ASTM 430 (430Nb) was annealed at 880 oC while the niobium and titanium bi-stabilized steel ASTM 439 was annealed at 925 oC. The annealed samples were tensile tested and due to the smaller grain size, steel 430Nb, showed a higher yield stress and a higher total elongation. Concerning drawability the steel ASTM 439 presented a better performance with higher average R-value, lower planar anisotropy coefficient and a greater value for Limit Drawing Ratio (LDR). These results are explained in terms of the differences in size and volume fraction of precipitates between the two steels.
Recrystallization Kinetics and Texture Evolution of Nb Stabilized Ferritic 430 Stainless Steel Cold Rolled and Isothermal Annealed
Authors: Malta Paula Oliveira , Moutinho Iane Dutra , Alves Davi Silva , Ferreira Aline Vasconcelos , Santos Dagoberto Brandão
Published: November 2016

The ferritic stainless steel type 430 stabilized with Nb, with and without annealing after hot rolling, was cold rolled and subjected to isothermal annealing at temperatures 650, 700 and 750°C for times ranging between 10 to 86400 s. The recrystallization kinetics was evaluated by JMAK model through microhardness measurements and KAM and GOS parameters. The Avrami exponent data indicate the occurrence of an unidimensional grain growth due only to high angle boundaries migration, with values ranging between 0.9 and 1.2. The nucleation rate and grain growth decreased continuously with time. The evolution of the texture was analyzed via EBSD analysis by ODF maps. The steel recrystallization is based on combination of ON and SG theories, due to presence of {111}<121>, {554}<225> and {111}<112> related to γ fiber. The rotated cube component, feature of the hot rolled steel, decreased with annealing time.
Re-Melting Technique with High Intense Pulsed Plasma Beams Applied for Surface Modification of Steel - Own Investigations
Authors: Sartowska Bożena , Barlak Marek , Walis Lech , Starosta Wojciech
Published: November 2016

The plasma beams were generated in a Rod Plasma Injector (RPI) operated in the Deposition by Pulsed Erosion (DPE) and Pulse Implantation Doping (DPE) modes. Samples of unalloyed and austenitic stainless steels were irradiated with short (μs scale) intense (energy density 2.0-5.0 J/cm2) pulses. The near surface layer - thickness in μm range - was melted and simultaneously doped with active element like nitrogen, cerium and lanthanum. Heating and cooling processes were of non-equilibrium type. The most important obtained results were: (i) austenitic structure was present in unalloyed steels after HIPPB modification processes and (ii) modified surface layers of austenitic stainless steel showed significant improvement of tribological properties and increase of high temperature oxidation resistance as compared with initial material.
X-Ray Stress Measurement of Austenitic Stainless Steel with cosα Method and Two-Dimensional X-Ray Detector
Authors: Sasaki Toshihiko , Sato Hikaru
Published: November 2016

This paper describes a fundamental experiment on X-ray stress measurement of austenitic stainless steel (JIS SUS316L) with a new equipment which was developed in this study. An image plate (IP) as a two-dimensional X-ray detector and the cosα method as a principle of the measurement of stress were used in it. An experiment was conducted with CrKβ characteristic X-ray and γFe-311 diffraction line, and the results were compared to those that were obtained with the conventional sin2ψ method under the similar X-ray conditions. It was found that the accuracy of stresses obtained with the equipment developed are almost as same as those of the sin2ψ method. However, the measuring time can be shorten by several times by using it.
GaN Thin-Film-Depositions on Glass and Amorphous-SiO2-Layer-Deposited Si Single-Crystalline Substrates
Authors: Sato Yuichi
Published: November 2016

Gallium nitride (GaN) transparent and semiconducting thin films were prepared on an amorphous glass substrate by a reactive sputtering method using Ar-N2 radio-frequency plasmas. In addition, GaN thin films were prepared on amorphous silicon-dioxide (SiO2) layer-deposited Si (111) single-crystalline substrates by a reactive evaporation method. Optical transmission properties, electrical properties, and crystallinities of the films prepared on the glass substrate were investigated as a function of the mixing ratio of the reactive sputtering gases. On the other hand, variations in the crystallinities of the films prepared on the amorphous SiO2 layer-deposited Si (111) substrates were investigated as a function of the thickness of the amorphous SiO2 layers.
IN792 DS Superalloy: Optimization of EB Welding and Post-Welding Heat Treatments
Authors: Barbieri Giuseppe , Soltani Peiman , Kaciulis Saulius , Montanari Roberto , Varone Alessandra
Published: November 2016

Electron beam (EB) welding has been used to realize the seams on 2 mm thick plates of directionally solidified (DS) IN792 superalloy. A grid of the samples has been prepared by varying the pass speed v from 1 to 2.5 m/min, while the other process parameters (power P = 1 kW, acceleration voltage T = 50 kV, beam current I = 20 mA) were kept constant. Experiments were carried out both at room temperature and with pre-heating at 200 °C or 300 °C.Once found the best process conditions (pre-heating at 300 °C; v = 2.5 m/min) the effect of post-welding heat treatments at 700 and 750 °C for increasing time up to 2 hours has been investigated.
Features of Electronic States in the Highly-Correlated Electronic System Sr1-xNdxMnO3 around x = 0.50
Authors: Shimasaki Rina , Shiratani Ayumi , Sato Hiroki , Inoue Yasuhide , Koyama Yasumasa
Published: November 2016

In the highly-correlated electron system Sr1-xNdxMnO3 (SNMO) having the simple perovskite structure, there are interesting electronic states, which are related to degrees of charge, orbital, and spin freedoms for eg electrons in Mn ions. Among these states, in the case of SNMO, the C-, A-and CE-type antiferromagnetic states were reported for 0.20 ≤ x ≤ 0.38, for 0.38 ≤ x ≤ 0.48, and for 0.48 ≤ x ≤ 0.52, respectively. The points to note here are that these antiferromagnetic states are directly associated with corresponding orbital orderings, and that the CE-type state also accompanies charge ordering. Because of these features, we were interested in the (A → CE) state change in SNMO. The crystallographic features of prepared SNMO samples with 0.46 ≤ x ≤ 0.50 have thus been investigated mainly by means of a transmission electron microscope equipped with a low-temperature holder. As a result, the state around 100 K for x = 0.48 was first understood to be identified as the Imma state, which includes a large number of orbital-modulated (OM) regions with an average size of about 10 nm. The feature of such regions is that the orbital modulation has an incommensurate periodicity and a charge modulation is absent in them. On the other hand, the CE-type state having the commensurate orbital and charge modulations was also confirmed to be present for x = 0.50. In addition to these two states, the state around 100 K for x = 0.46 was found to be characterized by the coexistence state consisting of the C-type orbital-ordered state and the Imma states including OM regions. In other words, the presence of the A-type orbital-ordered state could not be confirmed in the temperature range between 300 K and about 100 K for 0.46 ≤ x ≤ 0.50 in this study.
Development of a Biomimetic Metallic Femoral Stem: Methodological Approach
Authors: Brailovski Vladimir , Terriault Patrick , Simoneau Charles , Dumas Mathieu , Jetté Bruno
Published: November 2016

In this communication, a new methodological approach is proposed to develop a biomimetic metallic femoral stem. The design of this stem starts with the definition of an outer skin by reproducing the shape and overall dimensions of a Stryker® femoral stem to be implanted in an artificial femur model from Sawbones®. In-house algorithms are then used to generate two types of porous structures inside the outer skin: either a stochastic cubic-based porous structure or an ordered diamond-type porous structure. Next, a model of the femur-stem assembly is developed using the finite element method. The fully dense Stryker stem replica and two porous stems are fabricated using selective laser melting technology. Then, comparative mechanical testing is carried out using the ISO 7206-4 (2010) guidelines. These tests are conducted on an intact artificial femur (reference case) and on the identical femurs, but now implanted with the fully dense and porous stems. Using digital image correlation tools, the results of four series of tests are compared to assess which implant design leads to the lowest stress shielding in the implanted femur. Finally, the experimentally measured strain fields are compared to the numerical predictions to validate the numerical models.
The Issue of Grain Size Distribution Using Mean Field Models for Dynamic and Post-Dynamic Recrystallization
Authors: Smagghe Guillaume , Piot David , Montheillet Frank , Perrin G. , Montouchet A. , Kermouche G.
Published: November 2016

A mean field model for discontinuous dynamic recrystallization (DDRX) has been developed and chained with a post-dynamic recrystallization (PDRX) model to predict transient and steady-state flow stresses and average grain sizes. Numerical results are compared with experimental data obtained on a 304L stainless steel yielding to a good agreement in terms of average grain size. However an unrealistic grain-size distribution is observed using DDRX, which affects results of the PDRX model. This result is discussed with respect to the fundamental equations of DDRX.
Nb-Microalloying in Next-Generation Flat-Rolled Steels: An Overview
Authors: Speer John G. , Araujo Ana L. , Matlock David K. , de Moor Emmanuel
Published: November 2016

Extensive efforts are underway worldwide to develop new steels with substantial fractions of retained austenite, for lightweight automobile manufacturing and other applications requiring improved combinations of strength and formability. It is likely that microalloying can provide product enhancements in these emerging products, such as Q&P, TBF, medium-Mn TRIP, etc. and this paper examines the expected behavior of niobium using inferences based on published AHSS literature and principles of Nb microalloying. Some benefits of Nb in terms of microstructure refinement and precipitation strengthening have been reported. The potential influences of Nb are complex due to the sensitivity of Nb dissolution and precipitation to chemical composition and processing; differences in the expected role of Nb are pointed out with respect to different product forms produced via hot-rolling or annealing after cold-rolling, and microstructures with or without substantial quantities of primary ferrite. Some issues that warrant further examination are identified, as a deep understanding of Nb microalloying and other fundamental behaviors will be needed to optimize the performance of these next-generation steels.
The Effects of Intercritical Annealing Temperature and Initial Microstructure on the Stability of Retained Austenite in a 0.1C-6Mn Steel
Authors: Steineder Katharina , Krizan Daniel , Schneider Reinhold , Beal Coline , Sommitsch Christof
Published: November 2016

The effects of the intercritical annealing temperature and initial microstructure on the stability of retained austenite were investigated for a 0.1C-6Mn (wt-%) steel. Medium-Mn transformation-induced plasticity (TRIP) steels exhibit a strong dependence of their mechanical properties on the variation of intercritical annealing temperature. This behavior is strongly linked to the amount and stability of the retained austenite. Thus, interrupted tensile tests were used to examine the effect of annealing temperature on the stabilization of the retained austenite. Detailed microstructural investigations were employed to elaborate the effects of its chemical and mechanical stabilization. Furthermore, the final microstructure was varied by applying the batch annealing step to an initial non-deformed and deformed microstructure respectively. Retained austenite stability along with resulting mechanical properties of the investigated medium-Mn TRIP steel was significantly influenced as the amount and morphology of the respective phases altered as a consequence of both initial microstructure and applied intercritical annealing temperature.
Effect of As-Rolled Microstructure on Static Recrystallization Characteristics and Texture Evolution during Annealing
Authors: Su Jing , Kabir Abu S.H. , Yue Stephen
Published: November 2016

Magnesium AZ31 alloy sheets were rolled at 100 °C at a high rolling speed of 1000 m/min. After 30% reduction, the microstructure was heavily twinned and shear banded, while a partially dynamically recrystallized and twinned microstructure was seen at the reduction of 49%. The as-rolled specimens were then annealed at 500 °C for increasing times. Microstructure and texture were characterized by optical microscopy, electron backscattered diffraction (EBSD) and X-ray diffraction (XRD). Texture weakening was found during annealing of the specimens at both reductions. However, the texture weakening was more effective in the fully twinned and shear banded specimen than the partially DRXed and twinned specimen. Effects of as-rolled microstructure on static recrystallization characteristics and texture evolution during annealing were studied.
Use of Carbon Nanomaterials as a Catalyst Support in Fuel Cells
Authors: Suda Yoshiyuki
Published: November 2016

PtRu or Pt catalysts were supported on four types of carbon nanomaterials with different shapes, sizes, and graphitic and electrical properties, and their resulting catalytic activities were evaluated by electrochemical methods. The carbon nanomaterials used included two types of particles: Arc Black (AcB) and Vulcan XC-72R (Vulcan), and two types of nanofibers: carbon nanocoils (CNC) and VGCF-X. Pt and Ru were loaded onto the nanomaterials by a reduction method using sodium borohydride. Transmission electron microscopy and X-ray diffraction (XRD) revealed the PtRu catalyst particles to be 4–6 nm in diameters. The shifts in the Pt (111) XRD peaks of the catalysts on CNC and VGCF-X were larger than those on AcB and Vulcan, indicating a higher degree of alloying between Pt and Ru. The diameters of the CNC-supported Pt and PtRu catalyst particles had the narrowest distributions and were constant within the range of catalyst loadings investigated. Electrochemical studies of the catalysts during methanol oxidation were carried out using cyclic voltammetry. The catalyst particles supported on CNC and VGCF-X exhibited higher catalytic activity than those on AcB and Vulcan. The effect of the surface area of the carbon nanomaterials on the catalytic activity is discussed.
Influence of β-Mg17Al12 Phase on Initial Pitting Process of AZ91D Magnesium Alloy
Authors: Kaido Masahiro , Imai Kenta , Hatakeyama Masahiko , Sunada Satoshi
Published: November 2016

AZ91D magnesium alloy for casting is significantly corroded in chloride environment. In addition, Al-rich-α phase, which is formed during cooling process around β-Mg17Al12 phase, is one of the important factors on corrosion behavior in AZ91D. It is expected that pitting formation is dominant in the corrosion behavior in magnesium alloys. To clarify the influence of the Al-rich-α phase to pitting formation and corrosion behavior in AZ91D alloy, we have investigated the relationship between Microstructure and pitting formation in this study. We have carried out polarization curve measurement and scanning electron microscope (SEM) observation before and after the corrosion-tests.
SEM micrograph of as-cast samples showed AZ91D alloy consist of α phase, Al-rich-α phase which shows bright Z-contrast due to high Al contents and β phase. Al-rich-α phase formed around β phase. After the corrosion examination, holes were observed at Al-rich-α phase around the β phase, and it is thought that small pits grow up to be holes, because β phase is remained, while the Al-rich-α phase around the β phase preferentially dissolves with time. The result indicates that Al-rich-α phase around β phase enhance the formation of pitting and preferentially dissolve it in initial stage of corrosion in AZ91D alloy.
The Low-Nickel Cryogenic Steel Alloyed by Nitrogen
Authors: Svyazhin Anatoly G. , Kaputkina Ludmila M. , Smarygina Inga V.
Published: November 2016

New low-nickel Cr18Ni5Mn9Mo2N and Cr19Ni6Mn10Mo2N steels can be used up to-170 °C and differs in the highest level of durabilities in the hot-rolled and tempered from austenitic area state that provides its effective application in climatic conditions of the Arctic and Antarctic. Excess of durability over level, characteristic for traditional stainless steel of the Cr18Ni9 type, is provided due to additional solid solution hardening. Alloying with nitrogen to 0,18÷0,22% usual Cr18Ni9 steel has the smaller, but also high level of mechanical properties, differs in smaller thermal and mechanical stability of austenite and can be applied in less rigid on temperature and loadings service conditions. Corrosion resistance of austenitic stable steels free from contaminations is also higher compared to steel with regular cleanliness.
Design and Characterization of Conductive Biopolymer Nanocomposite Electrodes for Medical Applications
Authors: Tematio Charles , Bassas-Galia Mònica , Fosso Narcis , Gaillard Vanessa , Mathieu Marc , Zinn Manfred , Staderini Enrico M. , Schintke Silvia
Published: November 2016

Metal-based electrodes, despite being the most widely used for biomedical applications, are limited by a poor reliable skin-surface interface and patients suffer from comfort issues. The most common problems/inconveniences are caused by stiff electrodes, skin irritation, allergic reaction or corrosion. In order to overcome these problems, we produced and tested flexible electrodes involving biopolymer nanocomposite materials. Conductive polymers have been intensively studied and applied in the field of organic photovoltaics and flexible organic electronics. Recently, the use of conductive biopolymer nanocomposite has also emerged as an interesting and promising material for biomedical applications.
In this study, we have designed and characterized electrodes made of a flexible and conductive nanocomposite material using a biocompatible and biodegradable polymeric matrix of poly (3-hydroxyalkanoate) (PHA, in particular poly (3-hydroxybutyrate), PHB) containing conductive nanowires. The biopolymer nanocomposites and their electrical conductivities were investigated by optical microscopy, scanning electron microscopy (SEM) and electrical four-point probing. The electrical conductivities obtained in the different PHA-polymer nanocomposites containing different concentrations of conductive additives is discussed in relation to the nanocomposite structure at the microscopic level. Finally, our developed biopolymer nanocomposite prototype electrodes have successfully been tested for transcutaneous electrical nerve stimulation (TENS) and electrocardiography ECG applications in comparison to conventional electrodes.
Thermal Joining of Highly Conductive Bonds by Using Reactive Al-Ni Nanofoils
Authors: Theodossiadis Georgios D. , Wegner Maximilian , Zaeh Michael F.
Published: November 2016

In view of the demand for electrified long-range vehicles, the performance of traction batteries has to be improved. To achieve a high power density, the battery cells must be interconnected with low electrical resistance within the joints. The joining process has to fulfill specific requirements, as the battery cells may only be exposed to very low mechanical and thermal impacts.
Joining by using reactive aluminum-nickel nanofoils represents an innovative technology meeting the abovementioned requirements. These foils are multilayered systems consisting of several hundred alternating monolayers of aluminum and nickel, each with a thickness in the nanometer range. Their unique ability is that they can react with temperatures up to 1500 °C for a duration of a few milliseconds upon external ignition. This thermal reaction energy serves as a heat source in the joining process, melting the materials in the interfacial surface. Subsequently, the joining partners solidify and form an adhesive bond when compressed properly.
However, these advantageous characteristics are contrasted by complex reaction mechanisms and an unknown interaction of the process parameters. For the industrial application of the joining technology, the requirements for initiating the exothermic reaction must be known. Therefore, the process window and the mechanism of ignition have to be scrutinized. For this purpose, an experimental test setup was developed to generate and monitor short circuit currents to ignite the nanofoils. The amperage as well as the layer composition of the nanofoils were varied within a parameter study. Two independent process windows for a stable ignition were identified for all analyzed nanofoils.
Correlations between Defect Content, Mechanical Properties and Fractographic Investigation of AlSi9Cu3(Fe) Alloy Reference Castings
Authors: Battaglia E. , Bonollo F. , Tonello I. , Fiorese E.
Published: November 2016

High Pressure Die Casting (HPDC) is a foundry process particularly suitable for high production rates and applied in several industrial fields, but the amount of scrap, caused by defects or incomplete filling, is sometimes very high. Thus it is important to know which are the main causes of defect formation and their effects on microstructure and mechanical properties. This paper presents, within the European MUSIC project, the qualitative and quantitative results of a study conducted on AlSi9Cu3(Fe) alloy castings, referred to as Horse-shoe Reference Castings, specifically designed to generate different kinds of defects with different severity levels. The work focuses on the correlations obtained between the casting mechanical properties, their defect content in terms of porosity and oxide films and the process parameters adopted, mainly second phase plunger velocity and intensification pressure. The three point bending test was carried out on the four specimens obtained from the two appendixes of the casting. The fracture surfaces were studied by scanning electron microscopy (SEM) and optical microscopy (OM) highlighting that the defect content is clearly correlated to the mechanical properties and the process parameter settings.
Microstructure Evolution and Creep Properties of a Single Crystal Nickel-Based Superalloy with Various Orientations
Authors: Tian Su Gui , Su Yong , Yu Hui Chen , Shu De Long
Published: November 2016

By means of creep properties measurement and microstructure observations, the effect of microstructure evolution on creep strength of the single crystal Ni-based alloy with different orientations is investigated. Results show that, during creep at 1040 oC/137 MPa, the γ′ phase in [001]-oriented alloy is transformed into mesh-like N-type rafted structure, the one in [011]-oriented alloy is transformed into the stripe-like rafted structure along [001] direction, the one in [111]-oriented alloy is transformed into the mesh-like rafted structure along (010) plane. The γ′ phase with different configurations results in the different creep resistance of alloys, the sequence of creep resistance of alloys with different orientations are determined to be σ[001] > σ[111] > σ[011]. But after pre-compressed treated along [100] direction of [011] oriented alloy, the γ′ phase in [011] oriented alloy is transformed into the stripe-like rafted structure along [100] direction, which makes the creep life of the alloy enhancing from 11 h to 174 h at 850 oC/400 MPa, and from 74 h to 165 h at 1040 oC/137 MPa. This is attributed to the pre-treatment eliminating the gable channels to form the “labyrinth” structure of γ′ phase, which may increase the resistance of dislocation motion.
ω Phase Transformation and Mechanical Properties in Binary Zr-Nb Biomedical Alloy
Authors: Todai Mitsuharu , Fukunaga Keisuke , Nakano Takayoshi
Published: November 2016

The athermal ω phase transformation, magnetic susceptibility and deformation behavior of Zr-xNb alloys (x = 10 and 14) for use in medical devices subjected to magnetic resonance imaging (MRI) were investigated using electrical resistivity measurements, transmission electron microscopy observations and compression tests. The alloy with x = 10 exhibited a positive temperature coefficient in the electrical resistivity curve and the presence of an athermal ω phase at room temperature. On the other hand, the alloy with x = 14 showed an anomalous negative temperature coefficient (NTC) in the resistivity curve. Similar NTCs also appear in β-Ti alloys, which is interpreted as the growth of an athermal ω phase and the appearance of lattice modulation. The ω phase and diffuse satellites, which are possibly related to lattice modulation, were confirmed in the Zr-14Nb alloy at room temperature. The volume fraction of the athermal ω phase and the appearance of lattice modulation are related to the operating deformation mode and Young’s modulus. Thus, controlling the ω phase transformation in Zr-Nb alloys is key to developing medical devices that can be used in MRI.
Influence of Thermomechanical Treatment on the Damping Capacity of Selected Magnesium Alloys
Authors: Trojanová Zuzanka , Palček Peter , Chalupová Mária , Lukáč Pavel , Arlic Uwe
Published: November 2016

In the paper the temperature and amplitude dependence of internal friction in the AZ31, AZ63 and AZ91 alloys is reported. A rapid increase in internal friction with increasing temperature was estimated. Internal friction peaks were observed in AZ63 and AZ91 alloys. Position and height of the peaks in the temperature scale depends on the heating rate. Simultaneously, microstructural observations were performed in the selected points of the temperature scale. The amplitude dependence of internal friction in an AZ31 alloy, prepared by rolling, was measured. A significant influence of the rolling texture has been estimated. Main mechanisms of internal friction are connected with precipitation, dislocation motion and twinning.
Reverse Transformation Behavior Induced by Shot-Peening for SUS410S Martensitic Stainless Steel
Authors: Tsuboi Nagomi , Higa Serika , Sato Hisashi , Watanabe Yoshimi
Published: November 2016

Reverse transformation behavior of thermally-induced martensite phase (α’) in martensitic stainless steel by the shot-peening is investigated. It is found that volume fraction of austenite phase (γ) on the peened surface is increased by the shot-peening under elevated temperature. This means that reverse transformation from thermally-induced α’ to γ can be induced by the shot-peening. Moreover, with decreasing the distance between blast nozzle and specimen (blast distance), the reverse transformation occurs more remarkably. This is because that larger shear strain can be induced by the shot-peening with shorter blast distance. Furthermore, thickness of the deformation-induced layer becomes larger as the blast distance decreases. It can be concluded that the reverse transformation in SUS410S with thermally-induced α’ occurs by large shear strain during the shot-peening.
Early Instability Phenomena of IN792 DS Superalloy
Authors: Montanari Roberto , Tassa Oriana , Varone Alessandra
Published: November 2016

Microstructure stability of the directionally solidified Ni base IN792 superalloy has been investigated by Mechanical Spectroscopy (MS), i.e. internal friction (IF) and dynamic modulus measurements. Repeated IF test runs from room temperature to 1173 K have been carried out on the same samples and a Q-1 maximum has been always observed above 700 K. Its position does not depend on the resonance frequency. After each run the values of modulus and Q-1 at room temperature change indicating that a progressive irreversible transformation occurs. Damping phenomena have been attributed to the rearrangement of dislocation structures in disordered matrix which modifies dislocation density and average distance of pinning points. The results are supported by X-ray diffraction (XRD) and transmission electron microscopy (TEM) observations.
Effect of Heat Treatments on TiH2: Surface Composition and Hydrogen Release
Authors: Lapi Gabriele , Alvani Carlo , Varsano Francesca , Kaciulis Saulius , Montanari Roberto , Varone Alessandra , Gambini Marco , Vellini Michela
Published: November 2016

The present work investigates the effect of heat treatments in air on the surface and structure of titanium hydride (TiH2) and hydrogen desorption.
TiH2 has been heated in air at 440 and 540 °C for increasing time up to 180 min. to obtain the samples representative of 12 different oxidation conditions. The samples have been then examined by Temperature Programmed Desorption (TPD), X-Ray Diffraction (XRD) and Photoelectron Spectroscopy (XPS). Experimental results are presented and discussed.
Effects of Initial Micro-Structures on Deformation Behaviors of Commercial Pure Titanium
Authors: Wang Tong Bo , Li Bo Long , Li Mian , Nie Zuo-Ren
Published: November 2016

In this paper, effects of initial micro-structures on deformation behaviors of commercial pure titanium were elaborated by investigating the evolution of dislocation boundary and its adiabatic shear sensitivity. At the low to medium stain rates, the main plastic deformation mechanism of as-annealed commercial pure titanium is dislocation slipping. Meanwhile, geometrically necessary boundaries (GNBs) with different directions are generated and crossed with each other. However, new dislocation boundaries are formed in as-cold rolled plates, which are parallel to the initial ones induced by cold rolling. When the strain rate is up to 1000 s-1, the initial dislocation boundary playes an adverse role in the adiabatic shear sensitivity of commercial pure titanium. The adiabatic shear band is the high-speed deformation characteristic micro-structure in commercial pure titanium. In addition, dynamic recrystallized grains are generated in the center of an adiabatic shear band, which is consistent with the sub-grain rotation mechanism.
Microstructural Evolution of AZ31 under the Application of High Density Electric Current Pulses
Authors: Wang Xin Li , Liu Mei Shuai , Wu Nan , Dai Wen Bin , Zhao Xiang
Published: November 2016

The microstructural evolution in annealed Mg-3Al-1Zn (AZ31) magnesium alloy during high density electric current pulses (ECP) treatment is investigated by using a same current density with different processing numbers. It is found when the processing number of the ECP treatment is not greater than four times, the grains are refined and more homogenized, and the texture intensity obtained from the (0002) pole figure appears an obvious enhancement from 11.22 to 22.88. However, increasing the repeated ECP processing number will cause the coarsening of grain size and the decreasing of the texture intensity. The mechanism of the microstructural evolution during ECP treatment is discussed from the point of view of grain boundary motion.
Linear Friction Welding of IN718 to Ti6Al4V
Authors: Wanjara Priti , Gholipour Javad , Watanabe Kosuke , Nezaki Koji , Tian Y. , Brochu M.
Published: November 2016

Linear friction welding (LFW), an emerging automated technology, has potential for solid-state joining of dissimilar materials (bi-metals) to enable tailoring of the mechanical performance, whilst limiting the assembly weight for increased fuel efficiency. However, bi-metallic welds are quite difficult to manufacture, especially when the material combinations can lead to the formation of intermetallic (brittle) phases at the interface, such as the case with assembly of Ti base alloys with Ni base superalloys. The intermetallic phase, once formed, lowers the performance of the as-manufactured properties and its growth during elevated temperature service can lead to unreliable performance. In this project, it was demonstrated that linear friction welding can be applied to join Ti-6%Al-4%V (workhorse Ti alloy) to INCONEL® 718 (workhorse Ni-base superalloy) with minimized interaction at the interface. Of particular merit is that no intermediate layer (between the Ti alloy and Ni-base superalloy) was needed for bonding. Characterization of the bi-metallic weld included macro-and microstructural examination of the flash and interface regions and evaluation of the hardness.
Electron Beam Welding of High Strength Quenched and Tempered Steel
Authors: Weglowski Marek S. , Błacha Sylwester , Dymek Stanisław , Kopyściański Mateusz
Published: November 2016

The paper deals with the investigation of microstructure and mechanical properties of electron beam welded joints of high strength steel grades S690QL and S960QL in quenched and tempered condition. The microstructure of base metal was composed of bainite and martensite mixture at hardness about 270HV10 and 340HV10 for the S690QL and S960QL steels, respectively. The weldment was composed of several characteristic subzones revealed on the transverse sections. The central region of the weldment consisted mainly of coarse columnar dendritic grains which perpendicular to the fusion zone boundary. The microstructure of the heataffected zone near the fusion line consisted mainly of martensite, however, in both steels the microstructure varied with the distance from the fusion line. The tensile strengths of welded joints were Rm=850 MPa (S690QL) and 1074MPa (S960QL) and corresponded the tensile strengths of the base materials.
Saturation of Deformation Twinning in Magnesium Alloys
Authors: Wei Wen Wen , Povoden-Karadeniz Erwin , Kozeschnik Ernst
Published: November 2016

The saturation of primary tensile twins in heavily textured Mg-alloy AZ31 is investigated, and their strain accommodation limit is evaluated. EBSD results suggest that the mean number of twins per grain saturate rapidly, followed by the stop of twin growth. Twinning saturation is included in a physical model of twin evolution.
Numerical Simulation of Pore Evolution of 7050 Aluminum Alloy during Hot Compression Process
Authors: Wu Yong Fu , Jiang Hui Xue , Zou Chun , Yu Kang Cai , Nagaumi Hiromi
Published: November 2016

Evolution behavior of pores in 7050 aluminum alloy during hot compression process has been investigated by finite element (FE) numerical simulation. The representative volume element (RVE) model containing one isolated pore is built, in which the gas in pore is treated as ideal gas. Effects of initial pore inner pressure and deformation temperature on pore evolution have been investigated. The simulation results indicate that stress concentration exists around the pore in the compressing process. At the simple compression condition, the inner pressure of the pore increases but the volume decreases as the bulk metals deforms. However, the volume reaches a plateau after the yield point of bulk metal. The plateau volume depends on the initial inner pressure of the pore and the flow stress of the bulk metal. Since the inner pressure of the pore balances with the flow stress of bulk metal at the interface, the temperature affects the evolution behavior of the pore through its influence on the flow stress of the bulk metal primarily.
Microstructure of Fiber Laser Deposited WC-Co Cemented Carbide and Carbon Steel
Authors: Xu Pei Quan , Li Lei Jun
Published: November 2016

Using a fiber laser welding head, crack-free WC-Co/Steel weld depositions are obtained with optimized welding parameters. The microstructure, composition, phase, structure, and bend strength are analyzed using optical metallography, scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and bend test. The influence of the microstructure and WC/matrix interfaces in the vicinity of joint failure at the cemented carbide side is discussed. It is evident that the deposit consists of austenite dendrites and interdendritic eutectic carbides. The austenite further transforms to martensite on-cooling. The flexural bend strength and yield strength of the joints attained 970 MPa and 876 MPa, respectively. Bend fracture occurs at the HAZ in the cemented carbide side of the joint, characterized with cleavage fracture and quasi-cleavage fracture. TEM and HRTEM image of WC/Co interfaces verified the W2C and eta phase formation in the HAZ that contributed to the embrittlement.
Framework Structures for Mg Battery Cathodes
Authors: Yagi Shunsuke , Fukuda Masaaki , Ichitsubo Tetsu , Matsubara Eiichiro
Published: November 2016

Rechargeable Mg batteries have received intensive attention as affordable rechargeable batteries with high electromotive force, high energy density, and high safety. Mg possesses two valence electrons and has the lowest standard electrode potential (ca. -2.36 V vs. SHE) among the air-stable metals. There is another advantage that Mg metal can be used as an active material because Mg metal hardly forms dendrites. However, the slow diffusion of Mg ions in solid crystals prevents the realization of active materials for Mg rechargeable batteries at room temperature. Although some complex oxides have been reported to work as active materials at higher temperatures, Chevrel compounds are still the gold standards, which work at room temperature. However, the working voltage of the Mg battery using a Chevrel compound for the cathode is only ca. 1.2 V, which is far below that of Li-ion batteries (3-5 V). Nevertheless, Chevrel compounds have the significant advantage that a relatively large space exists in the crystal structure, which allows for fast Mg ion diffusion. In the present study, we investigated some materials with framework structures as cathodes for Mg batteries, which can alleviate the electrostatic constraint between Mg ions and cathode constituents. Specifically, we investigated the redox behavior of the thin films of Prussian blue and Prussian blue analogues in electrolytes containing an Mg salt using electrochemical quartz crystal microbalance and X-ray absorption spectroscopy. In addition, we discuss the electrochemical insertion/extraction behavior of Mg ions and their solvation structures.