bluuebunny/crossref_metadata_2025 huggingface dataset:
Friction Stir Welding for a Nuclear Fusion Reactor
Authors: Pramann Zak , Thompson Brian , Chrzanowski Jim , Mennel Dave
Published: May 2014

During a recent upgrade to the U.S. Department of Energy’s Princeton Plasma Physics Laboratory operates an experimental nuclear fusion reactor known as the National Spherical Torus Experiment (NSTX) a new center stack design was selected that required an innovative joining method to fabricate the bundled copper extrusions found in the center stack. Each of the 20-ft long copper extrusions used in the center stack was made from a quarter hard copper alloy (CDA10700) joined to lead extensions made from a high-strength copper alloy (CDA 18150). A team consisting of PPPL, Major Tool, and EWI selected Friction Stir Welding (FSW) to join these two materials together as its solid-state nature would provide a higher joint efficiency while minimizing distortion and preserving properties of the heat treatable lead extension flag.
Realization of Al/Mg-Hybrid-Joints by Ultrasound Supported Friction Stir Welding
Authors: Strass Benjamin , Wagner Guntram , Eifler Dietmar
Published: May 2014

To realize modern light weight constructions it is more and more necessary to combine the advantages of dissimilar materials. Fusion welding of dissimilar metals is in the most cases difficult or even impossible as a result of different melting points of the materials and the development of undesirable brittle intermetallic phases in the welding zone. This often leads to joint strengths considerable below the tensile strength of the base materials. By using Friction Stir Welding (FSW) as a pressure welding method, it is possible to reduce the development of the intermetallic phases of Al/Mg-joints significantly. But as calculated phase diagrams and high resolution microscopic SEM-investigations have shown it is not feasible to avoid them completely. The intermetallic phases form in the contact area very small continuous layers between the joining partners. On the other side it is known that ultrasonic energy can crack oxide layers. Hence a hybrid welding system at the Institute of Materials Science and Engineering (WKK) at the University of Kaiserslautern was developed called “Ultrasound Supported Friction Stir Welding (US-FSW)” with the aim to shatter the brittle interlayer lines and to scatter fragments in the welding area during the FSW process. Pre-investigations have shown that for US-FSW-joints between Al wrought alloys and Mg cast alloys the strength can be increased up to 30% in comparison to conventional friction stir welds. Currently, further investigations are carried out with joints between AC-48000 and AZ80.
FSW Process Tolerance According to the Position and Orientation of the Tool: Requirement for the Means of Production Design
Authors: Zimmer-Chevret Sandra , Jemal Nejah , Langlois Laurent , Ben Attar Amarilys , Hatsch Jonathan , Abba Gabriel , Bigot Régis
Published: May 2014

Friction Stir Welding (FSW) is an innovative welding process increasingly used by industry for the welding of aluminum alloys. In order to reduce the high investment costs of a dedicated FSW’s machine and in order to offer more flexibility to weld complex geometry, high payload robots may be used. A serial kinematics robot meets these specifications but under the stresses generated during welding, its structure readily deforms. The consequences are deviations of the tool nominal position with respect to the seam. The work presented here proposes to study the process tolerances with tool positioning defect. An experimental study enables to evaluate the influence of the tool position disorientation on weld quality, the travel force and torque generated. The objective is to estimate the impact of the disorientation on the tool mechanical interactions when welding using a serial kinematics robot.
Separation of Pure Silicon from Al-Si Alloy Melts
Authors: Kim Ki Young , Shin Jong Sik , Park Dong Wha
Published: May 2014

Pure silicon can be obtained from Al-Si alloys by a combination of solvent refining and centrifugation. Primary silicon crystals are separated in the form of a foam after centrifugation. A vertical centrifugal separator is used which needs no more effort for further separation since each part of the high and low silicon content is divided automatically into two pieces after centrifugation. This centrifugal method does not use the density difference between two phases as in other methods, but uses the order of solidification in Al-Si alloys. How to make the Si foam, its characteristics including its density and strength, and purity of the extracted Si particles after acid leaching are reviewed.
Experimental Studies on Melting Behavior of Silicon Powders by In-Flight Plasma Melting Technique
Authors: Yoo Shin , Moon Ki Hyeon , Hyun Seong Yoon , Won Seo Kyung , Shin Geon
Published: May 2014

An experimental approach has been used to investigate the charateristics of silicon type powders using heat source of thermal plasma. In this paper, laboratory scale furnace (0.0529m3) using non-transferred hollow thermal plasma torch (150kW) is applied for the rapid melting and the impurities components volatilization. The components and the crystallization behavior of silicon type raw material for complete melting using in-flight melting technique with continuous powder feeding (500~1000 g min-1) into the furnace are investigated by changing the melting atmosphere. The determination of impurities absorption and erodability of the furnace caused by the extremely high localized tempeartures of plasma heat source and molten material is also followed.
Analysis of Cooperativity in Metallic Glass Forming Liquids
Authors: Aniya Masaru , Ikeda Masahiro
Published: May 2014

The relation between fragility and cooperativity of atomic motion in bulk metallic glass forming liquids is studied based on the bond strength-coordination number fluctuation model. The model describes the temperature dependence of the viscosity in terms of the mean values of the bond strength, coordination number and their fluctuations of the structural units that form the melt. According to the model, the cooperativity increases with the increase of fragility. The model estimates that the magnitude of the cooperativity NB extends approximately from 7 to 60 structural units, depending on the material. The temperature dependence of NB for different metallic glass forming systems reveals that NB increases with the decrease of temperature. The relation between NB and diffusivity of atoms is discussed briefly.
The Evolution of Texture and Deformation Anisotropy at an Equal Channel Extruded Aluminum 1050 Alloy
Authors: Sussai W.R. , Bolmaro R.E. , Kliauga Andrea Madeira
Published: May 2014

The aim of this work was to analyze the evolution of texture and the deformation anisotropy of a AA1050 after ECAP and further recrystallization. The initial material was processed by two different routes: the first set of samples came from a hot rolled band with a mixture of cube, copper and brass textures and the second from roll casting and presented a strong brass texture. The ECAP deformation followed routes A, Ay (no rotation between passes but keeping the normal to rolling direction parallel to the transverse extrusion axis) and Bc. Texture evaluation was performed by x-ray analysis. Results were analyzed by regular texture and orientation distribution function calculations. The deformation anisotropy was measured by tension tests with specimens oriented 0, 45 and 90o to the extrusion direction.
Production of Zr-Based Metallic Glass Matrix Composites by Semisolid Process
Authors: Tamura Takuya
Published: May 2014

It was reported that micrometer-sized ductile crystalline phases can improve the ductility of Zr-based bulk metallic glasses. The present authors reported the synthesis of bulk metallic glass composites by a process combining cooling slope casting and suction casting for Zr66.4Nb6.4Cu10.5Ni8.7Al8 alloys. This study aims to investigate basics of Zr-based metallic glass matrix composites with semisolid structure. As a result, it was found that the Zr-based metallic glass matrix composites with very uniform semisolid structure can be produced by heat treatment process at semisolid region. Moreover, it was found that experimental results can be explained by the pseudo-binary phase diagram.
Shape Memory Behavior of Zr-Cu-Al Bulk Metallic Glass Matrix Composite
Authors: Hitoo Tokunaga , Kazutaka Fujita , Yokoyama Yoshihiko
Published: May 2014

Zr-Cu-Al bulk metallic glass matrix composite with the intermetallic compound ZrCu (B2) phase was fabricated. The effect of the ZrCu phase on mechanical properties and deformation behavior of the composite was investigated by compressive test. Also, phase transformation behavior of the ZrCu phase was analyzed by X-ray diffraction. Furthermore, macroscopic shape memory behavior was investigated using the composite by three point bending test. As the results, it was found that the mechanical properties of the composite depend on the volume fraction of the precipitated ZrCu phase. Compressive strength and yield stress of the composite decrease with increase of volume fraction of the ZrCu phase. On the other hand, plastic strain increases with increase of volume fraction of the ZrCu phase. In addition, it was confirmed that a stress-induced martensitic transformation of the ZrCu phase occurs by compressive stress loading. Furthermore, it was found that the composite with high volume fraction of the ZrCu phase exhibits shape memory effect.
Correlation between the Enhanced Plasticity of Glassy Matrix Composites and the Volume Fraction, Size and Intrinsic Mechanical Property of Reinforcements
Authors: Chu Z.H. , Kato Hidemi , Xie Guo Qiang , Yan D.R. , Yuan Guang Yin
Published: May 2014

In recent years, bulk metallic glasses (BMGs) have received considerable attention due to their unique mechanical properties. However, the deformation of BMGs is highly localized in a few shear bands so that many of them exhibit poor plasticity. As such, more and more researchers have focused on improving the plasticity by in-situ or ex-situ introducing of nanoor micro-scale crystalline phases into the metallic glassy matrix in order to formation of multiple shear bands.
Preparation of ATO Thin Films from SPS-Derived Large Size ATO Ceramic Targets by PVD Methods
Authors: Chen Fei , Wu Jun Yan , Shen Qiang , Schoenung Julie M. , Zhang Lian Meng
Published: May 2014

Good crystalline of ATO thin films is necessary to improve the electrical and optical properties. In this paper, ATO thin films were fabricated using PLD method at high temperature of 550 °C, and the effect of laser energy density on the microstructure, electrical property and optical property of the ATO films is discussed. The results suggest that ATO films show good crystalline when deposited at high temperature of 550 °C. Both the electrical and optical properties have been enhanced with the increasing of laser energy density. When the laser energy density is 5.4 J/cm2, the lowest resistivity of ATO thin film is obtained with the value of 6.52×10-4 Ω·cm and the average optical transmittances is 82.0 %.
Synthesis of Nanoporous Materials and their Functionalization for Environmental Applications
Authors: Ramírez Adriana Medina , Melo Prócoro Gamero , Robles José Manuel Almanza
Published: May 2014

In this work, W, P and faujasite zeolites were synthesized using fly ash as raw material, a waste material derived of coal fired plants in Mexico. Two different synthesis methods were used. Zeolites were submitted a functionalization treatment exchanging their metallic ions by ammonium, aluminum and ferrous ions. Chemical, structural and textural properties of functionalized zeolites were evaluated. As (V) and As (III) adsorption capacity of modified zeolites were assessed. Changes on their structural properties were no significant. While the textural properties such as pore volume, specific surface area and pore size distribution were dependent of nature of ion exchanged, and the accessibility of extra-framework sites of the zeolites. Functionalization with di and trivalent ions allow changing the zeolitic surface charge. This modification led to increase their ability to adsorb anionic species from aqueous solutions. The results shown that, the adsorption capacity was dependent of zeolite type and their chemical surface nature. W zeolite modified with aluminum ions achieved the highest arsenic (V) adsorption capacity. While ferrous functionalization on W zeolite shown a high affinity to remove As (III) species from aqueous solutions.
Nanostructure Control of Si and Ge Quantum Dots Based Solar Cells Using Plasma Processes
Authors: Shiratani Masaharu , Uchida Giichiro , Seo Hyun Woong , Ichida Daiki , Koga Kazunori , Itagaki Naho , Kamataki Kunihiro
Published: May 2014

We report characteristics of quantum dot (QD) sensitized solar cells using Si nanoparticles and Ge nanoparticles. Si nanoparticles were synthesized by multi-hollow discharge plasma chemical vapor deposition, whereas Ge nanoparticles were done by a radio frequency magnetron sputtering using Ar+H2 under high pressure conditions. The electrical power generation from Si QDs and Ge QDs was confirmed. Si QD sensitized solar cells show an efficiency of 0.024%, fill factor of 0.32, short-circuit current of 0.75 mA/cm2 and open-circuit voltage of 0.10 V, while Ge QD sensitized solar cells show an efficiency of 0.036%, fill factor of 0.38, short-circuit current of 0.64 mA/cm2 and open-circuit voltage of 0.15 V.
Multiscale Analysis of Acoustic Emission during Plastic Flow of Al and Mg Alloys: From Microseconds to Minutes
Authors: Lebyodkin Mikhail , Shashkov Ivan V. , Lebedkina Tatiana , Gornakov Vladimir S.
Published: May 2014

Recent studies of plastic deformation using high-resolution experimental techniques bear witness that deformation processes are often characterized by collective effects emerging on an intermediate scale between the scales describing the dynamics of individual crystal defects or the macroscopic plastic flow. In particular, the acoustic emission (AE) reveals intermittency of plastic deformation in various experimental conditions, which is manifested by the property of scale invariance, a characteristic feature of self-organized phenomena. Some materials, e.g., Al or Mg alloys, display a macroscopic discontinuity of plastic flow due to the Portevin-Le Chatelier effect or twinning. These materials are therefore of special interest for the study of collective effects in plasticity. The present work reviews the results of a multiscale investigation of AE accompanying plastic deformation of such model alloys. The AE is analyzed by methods borrowed from the theory of nonlinear dynamical systems, including statistical and multifractal analyses.
Catalytic Properties of Ni-Al Intermetallic Nanoparticles Fabricated by Thermal Plasma Process
Authors: Xu Y. , Yang Jun You , Demura Masahiko , Hirano Toshiyuki , Matsushita Yoshitaka , Tanaka Masahiko , Katsuya Yoshio
Published: May 2014

The catalytic activity of Ni-Al (Ni25Al) nanoparticles fabricated by thermal plasma evaporation was examined for methanol decomposition and CO oxidation. The nanoparticles exhibited high activity for both reactions. Characterization of the nanoparticles revealed that the fabricated nanoparticles were mainly comprised of Ni and Ni3Al phases. During CO oxidation, the Ni phase was oxidized to NiO, while the Ni3Al phase remained unchanged. The NiO phase is supposed to serve as the active sites for CO oxidation. In contrast, during methanol decomposition, no obvious oxidation was observed for both Ni and Ni3Al phases. The Ni and Ni3Al phases are supposed to contribute to the high activity for methanol decomposition.
Utilization of an Event-Recording System for Neutron Diffraction Experiments
Authors: Ito Takayoshi , Harjo Stefanus , Inamura Yasuhiro , Nakatani Takeshi , Kawasaki Takuro , Abe Jun , Aizawa Kazuya
Published: May 2014

We present effectivity of an event-recording system in neutron diffraction experiments at the Engineering Materials Diffractometer TAKUMI at the Materials and Life Science Experimental Facility in J-PARC. We developed an event-recording system for recording information of neutron generation and detection and sample environmental conditions like load, strain, etc. as events with synchronized timing tag across whole system, and developed a software to handle the event data. It gave us several advantages by allowing us flexible data reduction depending on users’ purposes, especially for time resolved experiments. We demonstrated in situ neutron diffraction measurements using these new recording system and software to show the advantages. These new system and software are very attractive to be applied for measurements that need stroboscopic data collection such as fatigue tests.
The Use of In Situ Characterization Techniques for the Development of Intermetallic Titanium Aluminides
Authors: Mayer Svea , Schwaighofer Emanuel , Schloffer Martin , Clemens Helmut
Published: May 2014

Urgent needs concerning energy efficiency and environmental politics require novel approaches to materials design. One recent example is thereby the implementation of light-weight intermetallic titanium aluminides as structural materials for the application in turbine blades of aero-engines as well as in turbocharger turbine wheels for the next generation of automotive engines. Each production process leads to specific microstructures which can be altered and optimized by thermo-mechanical processing and / or subsequent heat-treatments. To develop sound and sustainable processing routes, knowledge on solidification processes and phase transformation sequences in advanced TiAl alloys is fundamental. Therefore, in-situ diffraction techniques employing synchrotron radiation and neutrons were used for establishing phase fraction diagrams, investigating advanced heat-treatments as well as for optimizing thermo-mechanical processing. Summarizing all results a consistent picture regarding microstructure formation and its impact on mechanical properties in advanced multi-phase TiAl alloys can be given.
The Influence of Thermomechanical Controlled Processing on Bainite Formation in Low Carbon High Strength Steel
Authors: Liang Xiao Jun , Hua Ming Jian , DeArdo Anthony J.
Published: May 2014

Thermomechanical controlled processing is a very important way to control the microstructure and mechanical properties in low carbon, high strength steel. This is especially true in the case of bainite formation, where the complexity of the austenite-bainite transformation makes the control of the processing important. In this study, a low carbon, high manganese steel containing niobium was investigated to better understand the roles of austenite conditioning and cooling rates on the bainitic phase transformation. Specimens were compared with and without deformation, and followed by seven different cooling rates ranging between 0.5°C/s and 40°C/s. The CCT curves showed that the transformation behaviors and temperatures are very different. The different bainitic microstructures which varied with austenite deformation and cooling rates will be discussed.
Analysis of Retained Austenite and Residual Stress Distribution in Ni-Cr Type High Strength Steel Weld by Neutron Diffraction
Authors: Sueyoshi Hitoshi , Ishikawa Nobuyuki , Inoue Hiroshige , Hiraoka Kazuo , Kasuya Tadashi , An Ke , Skorpenske Harley
Published: May 2014

Prevention of weld cracking is necessary for ensuring the reliability of high strength steel structures. Tensile residual stress in the weld metal is one of the major factors causing the weld cracking, therefore, it is important to clarify the residual stress distribution in the weld metal. Conventional stress measurement, the stress relief method using strain gauges and the X-ray diffraction technique, can only provide the stress information in the surface region of the steel weld. The neutron diffraction is the only non-destructive method that can measure the residual stress distribution inside the steel weld [1-3]. The neutron stress measurement was applied for the 980MPa class high strength steel weld and it was revealed that high level of tensile residual stress can affect the weld cracking to a significant degree [4-5]. Recently, it was reported that Ni-Cr type steel weld exhibit higher resistance to the weld cracking compared with conventional low alloy type weld. Increase of tensile residual stress is prevented by lower transformation temperature of the Ni-Cr type weld metal and retained austenite phase is dispersed in the martensite microstructure. It is considered that lower level of tensile residual stress and the existence of retained austenite may prevent hydrogen accumulation in the weld metal [6]. However, retained austenite and the residual stress conditions in the Ni-Cr type high strength steel weld is not well understood. In this study, neutron diffraction analysis was conducted on the Ni-Cr type steel weld joint with the tensile strength level of 980MPa in order to investigate the effect of the retained austenite and the residual stress distribution on the weld cracking.
Grain Competitive Growth Prediction during Solidification in Single Crystal Superalloy DD6 Castings
Authors: Jin Hai Peng , Li Jia Rong
Published: May 2014

Competitive growth and grain selection were simulated and analyzed during the directional solidification with the conditions for single crystal superalloy DD6 castings using Commercial software, ProCAST. A three dimensional cellular automaton (CA) model coupled with finite-element (FE) heat flow calculation was applied. Measurements at the grain scale were made using the EBSD method at the cross sections in the starter block and grain selector at an interval of 4 mm from the chill surface. The grain characteristics and the rules of competition growth were obtained. The validity of the simulation results were compared with those of the experiment. It concluded that the model-predicted tendency shows satisfactory agreement with the experiment. Increasing the distance from the chill decreases the number of grains, increases the radius of grains and drives the crystallization orientation of grains to principal stress orientation.
Towards a 3-Dimensional Phase-Field Model of Non-Isothermal Alloy Solidification
Authors: Mullis Andrew M. , Bollada Peter C. , Jimack Peter K.
Published: May 2014

We review the application of advanced numerical techniques such as adaptive mesh refinement, implicit time-stepping, multigrid solvers and massively parallel implementations as a route to obtaining solutions to the 3-dimensional phase field problem for coupled heat and solute transport during non-isothermal alloy solidification. Using such techniques it is shown that such models are tractable for modest values of the Lewis number (ratio of thermal to solutal diffusivities). Solutions to the 3-dimensional problem are compared with existing solutions to the equivalent 2-dimensional problem.
Martensite Spread: Analytical Modeling and Computer Simulation
Authors: Rios Paulo Rangel , da Silva Drumond Gustavo , Neves Tiago , Guimarães José Roberto Costa
Published: May 2014

In bulk polycrystals, the ﬁrst nucleation event in a single grain may induce transformationin neighboring grains, resulting in a cluster of partially transformed grains. This cluster of partiallytransformed grains is normally designated as a ‘spread event’. The collection of these single spreadevents can be deﬁned as the ‘spread’or ‘martensite spread’. In this paper we show how the martensitespreadmay be well described by formal kinetics. Spread taking place as a result of athermalmartensitetransformation, isothermal martensite transformation and even martensite burst are analyzed with thehelp of such a methodology. Formal kinetics is essentially based on a stochastic geometry approach ofthe transformations considered as nucleation and growth (or birth-and-growth ) processes. Therefore,the success of such an analysis strongly suggests the possibility of a computer simulation of the spreadentirely based on probabilistic considerations. Such a simulation has been carried out and the resultsare discussed in this paper with reference to the results obtained by the analytical methods.
Use of Electronic Stress Tensor Density and Energy Density in Chemistry
Authors: Ichikawa Kazuhide , Nozaki Hiroo , Tachibana Akitomo
Published: May 2014

The concepts of electronic stress tensor density and energy density give new viewpoints for conventional ideas in chemistry. In this paper, we introduce the electronic stress tensor and energy density and other related quantities such as tension density and kinetic energy density, which are based on quantum field theory, and show their connection to the concepts in chemistry. The topics are: (i) zero surface of the electronic kinetic energy density and size of atoms, (ii) separatrix of the tension field as a boundary surface of atoms in a molecule, (iii) interpretation of energy density based bond order as directional derivative of a total energy of a molecule regarding the bond direction, and (iv) eigenvalues of the stress tensor as tools to classify types of chemical bond.
Microstructure Evolution and Precipitation Modeling in Ni-Based Alloy C-263
Authors: Vujic Stojan , Di Martino S.F. , Matera Susanna , Tassa Oriana , Hogg Simon , Zurek Joanna , Beal Coline , Sommitsch Christof
Published: May 2014

Due to its high creep strength and oxidation resistance, C-263 is a promising Ni-based alloy for applications in superheater tubes in coal fired thermal power plants. The creep strength is mostly based on finely distributed gamma-prime precipitates. In this work, the microstructural evolution of this material during heat treatment and thermal ageing has been investigated. The investigations were carried out by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Selected Area Diffraction Pattern (SADP) and Energy Dispersive Spectroscopy (EDS). Besides, equilibrium and Scheil calculations were carried out using the thermodynamic software MatCalc to analyze the stable phases and the solidification process, respectively. Precipitation calculations during solution annealing and subsequent ageing at 700°C and 750°C up to 10.000h ageing time were performed to predict the phase fraction and precipitates radius. SEM and TEM investigations of aged specimens revealed three different precipitates: M23C6, γ’ and MX. MatCalc also predicted these precipitates. The calculated phase fraction and mean radius show good agreement with experimental data.
Hybrid Modelling Approach for Investigating the Thermal Contact during Solid State Joining
Authors: Wang Hua , Colegrove Paul A. , Dos Santos Jorge Fernandez
Published: May 2014

In FSW modelling, two major approaches have been used to describe the heat loss from the workpiece to the backing bar. The first method simplifies the heat loss using a convective transfer and has been used by some researchers such as Khandkar et al.[1]. The second method uses a contact gap conductance to represent the imperfect contact at the interface between the workpiece and the backing bar [1-3]. The contact gap conductance, k is defined as: k = Q/(T0-TA), where Q is the heat flux from the workpiece to the backing bar, TO is the temperature of the workpiece and TA is the temperature of the backing bar. Khandkar et al.[1] found that using the contact gap conductance method was more accurate than the convective heat transfer coefficient. Both Simar et al.[2], Colegrove and Shercliff [3] and Shi et al.[4] have used a variable contact gap conductance in their models. Shi et al.[4] applied a temperature dependent contact gap conductance method where the value increased with temperature to simulate the better contact under the tool. This paper combined the FSW process model with Artificial Neural Network (ANN) models to find the temperature dependent contact gap conductance k which is named as a hybrid models.
On Fatigue Crack Initiation in the Matrix in Very High Cycle Fatigue Regime
Authors: Chai Guo Cai
Published: May 2014

In very high cycle fatigue, VHCF, regime, fatigue crack initiation can occur at subsurface defects such as inclusion or subsurface non-defect (matrix) origin. This paper provides a study on the fatigue crack initiation mechanisms at subsurface non-defect (matrix) origin in two metallic materials using electron backscatter diffraction and electron channeling contrast imaging. The results show that the strains in the material in the VHCF regime were highly localized, where the local maximum strain is greatly higher than the average strain value. This high strain localization can lead to the formation of fine grain zone and also fatigue damage or fatigue crack initiation at grain boundaries or twin boundaries by impingement cracking. High strain localization is caused by strain accumulation of each very small loading, and also increases the local hardness of the material. This may start quasi-cleavage crack origin, and consequently the formation of subsurface fatigue crack initiations. The results also show that fatigue damage and crack initiation mechanisms in the VHCF regime can be different in different metals due to the mechanisms for local plasticity exhaustion.
New Algorithm to Determine the Yield Stress from FIMEC Test
Authors: Ciambella Laura , Montanari Roberto
Published: May 2014

The indentation test is one of the most common techniques for the mechanical characterization of materials. Different tests have been standardized, depending on punch geometry and indentation parameters, and different models have also been set up to predict indentation hardness and to estimate uni-axial mechanical properties for all the geometries (cone, wedge, pyramid, sphere, etc.).
A flat-ended cylindrical indentation technique (FIMEC) has been developed by one of the present authors. FIMEC employs a cylindrical punch with diameter ranging from 3.0 to 0.5 mm and gives pressure-penetration curves from which yield stress and elasticity modulus can be determined. The specific characteristics of FIMEC are: 1-the high simplicity of the apparatus; 2-the possibility to get information about the local material properties on a scale large enough to include many grains (data represent bulk characteristics and are not influenced by those factors which dramatically affect micro-and nanoindentation tests); 3-the large versatility in industrial applications such as the control of welding quality, 4-the on-line monitoring of forging or extrusion processes etc..
This paper describes a new algorithm developed to calculate the yield stress from FIMEC curves. To assess the reliability of the method, it has been tested on several metals of known characteristics and the scattering of data with respect those from tensile tests resulted to be within ±7%.
Influence of SDAS on the High Temperature Tensile Behaviour of the C355 Al Alloy
Authors: Ceschini Lorella , Jarfors A. , Morri A. , Morri A. , Rotundo F. , Seifeddine S. , Toschi S.
Published: May 2014

The aim of the present study was to characterize the high temperature tensile behaviour of the C355 (Al-Si-Cu-Mg) alloy produced under controlled casting condition so as to obtain different secondary dendrite arm spacing (SDAS). C355 samples were produced through a gradient solidification equipment able to produce microstructures with fine (20-25 μm) and coarse (50-70 μm) SDAS values. The as-produced specimens were subjected to hot-isostatic pressing and then T6 heat treated. Microstructural characterization, room and high temperature (200 °C) tensile tests were carried out on the heat treated specimens. The tensile behaviour was related to the different SDAS value of the samples.
Computation of Wave Propagation in Damped Specimen for Damage Detection
Authors: Jawali Veena , Parasivamurthy Prakash , Nagesh Ashwini
Published: May 2014

Aim of a structural health monitoring system must be to collect sufficient information about the damage for appropriate remedial measures to be taken to ensure safety. The preliminary step in the process of damage assessment is locating the damage .One of the challenges faced by the structural health monitoring system is monitoring in-flight damages. Localization of in-flight damages or sudden impacts can be achieved by monitoring the acoustic emissions in real time mode. In this paper, an approach based on the employment of Piezo-electric transducer rosettes to locate the acoustic emission source in an aluminum plate is presented. Using the strain gage rosette concepts adapted for piezoelectric transducers, the wave strain principal angles are determined. When two rosettes are used, the intersection of the principal wave strain directions detected by the rosettes gives the wave source location. The method does not require the knowledge of wave velocity in the medium in contrast to the time of flight based location. Hence, this technique can be used in anisotropic or complex structures where the source localization using the conventional time of flight method is difficult. The principal strain angle using the voltage response of the transducers and the rosette principles are obtained and the co-ordinates of the wave source location are calculated using the co-ordinates of the centroids of the rosettes in MATLAB.According to the tests, the rosette piezo-transducer outperforms the single piezo elements to a degree justifying its complexity. The rosette piezo transducer provides more damage related information compared to single elements and hence the performance of the damage detection system can be significantly improved if rosettes are used.
Analysis of Environmental Performance of Green Geosynthetics Based on Degradability
Authors: Jeon Han Yong
Published: May 2014

In this study, concept of green geosynthetics was introduced in terms of biodegradability. Development of green geosynthetics, its background and technical concerns were discussed through some research results of PLA(polylactic acid) specimens. Test method for biodegradability of PLA(polylactic acid) as a green geosynthetics were considered and suggested based on composting method. Finally, the rest result shows that the concept of biodegradability for green geosynthetics is available in the environmental application. PLA 4032D/PBAT(80/20) blend shows improvement of environmental performance as a green geosynthetics application than PLA 4032D only used.
Application of Indirect Laser Peening to SUS304 Stainless Steel
Authors: Kawakami Hiroshi , Kondo Akiyoshi , Kutsuna Muneharu , Saito Kiyotaka , Inoue Hiroki , Ozaki Hitoshi , Suzuki Jippei
Published: May 2014

Indirect laser peening applied to the substrate of austenitic stainless steel with the sheet of similar material. Effects of indirect laser peening condition on the formation of the dimple and the residual stress were investigated in this paper. Shape of the dimple and distribution of the residual stress were measured by laser microscope and X-ray diffraction, respectively. It was observed by the microscope that clean substrate surface of as-received state kept after indirect laser peening because of protection by the sheet. However, fracture of sheet occurred slightly in high pulse energy condition. The diameter and the depth of the dimple by indirect laser peening increased with the increase of laser power. Efficiency of dimple formation decreased with the increase of pulse energy. Affective condition region of indirect laser peening with a combination between the substrate and the sheet of austenitic stainless steel may be limited below the laser power density of 10GW/cm2. It was confirmed that indirect laser peening induced compressive residual stress in the substrate. One of peak of compressive residual stress in residual stress distribution existed near the bottom of the dimple. Residual stress distribution which was produced by indirect laser peening may affect change of quasi bending modulus which was obtained by three-point bending test.
Microstructural Characteristics of Diecast AlMgSiMn Alloy
Authors: Ji Shouxun , Wang Yun , Watson Douglas , Fan Zhong Yun
Published: May 2014

Solidiﬁcation and microstructural characteristics of Al-5wt.%Mg-1.5wt.%Si-0.6wt.%Mn-0.2wt.%Ti alloy have been investigated in high pressure die casting. The average size of dendrites and fragmented dendrites of the primary α-Al phase formed in the shot sleeve is 43 m, and the globular α-Al grains formed inside the die cavity is 7.5 m. Solidification inside the die cavity also forms the lamellar Al-Mg2Si eutectic phase and the Fe-rich intermetallics. The size of the eutectic cells is about 10 m, in which the lamellar α-Al phase is 0.41 m thick. The Fe-rich intermetallic compound exhibits a compact morphology and is less than 2 m. Calculations using the Mullins and Sekerka stability criterion reveal that the solidiﬁcation of the primary α-Al phase inside the die cavity has completed before the spherical α-Al globules begin to lose their stability, but the α-Al grains formed in the shot sleeve exceed the limit of spherical growth and therefore exhibit a dendritic morphology.
High Performance Materials by Laser Deposition
Authors: Newkirk Joseph W. , Liou F. Frank
Published: May 2014

Additive Manufacturing using laser deposition has a great deal of attractiveness as a fabrication technique for metals and alloys. The combination of a high heat input, small molten volume, and incremental addition also is well suited for the production of high performance alloys and composites. The high cooling rates inherent in the process produces refined microstructures, leading to excellent as-deposited mechanical properties in conventional alloys. The high heating rates and cooling rates potentially lends itself to structurally amorphous alloys, functionally gradient materials, and nanostructured materials, among other more exotic metallic materials. By monitoring the process a map of the quality of the build can be recorded for quality assurance and validation. Flaws detected during fabrication can then be repaired in-situ. Realizing this potential will require a combination of modeling, experimental validation, and new design paradigms. Together this will lead to the greatest properties and functionalities in future products.
RETRACTED: Microstructural Characterization and Mechanical Properties of Laser Deposited High Entropy Alloys
Authors: Sistla Harihar , Newkirk Joseph W. , Liou F. Frank
Published: May 2014

RETRACTED PAPER: High entropy alloys have attracted great interest due to their flexibility in composition accompanied with very interesting properties, which make these materials candidates for further research. The formation of single solid solution phases as a preference to complex mixtures of intermetallic phases leads to good mechanical and thermal properties. Additive manufacturing in the form of Laser deposition presents us with a very unique way to manufacture near net shape metallic components with advanced materials. The present study focusses on the characterization of High entropy alloys manufactured through laser deposition. The alloy system considered for this study is (AlFeCoCrNi). The ratio of aluminum to nickel was decreased to observe the transition of the solid solution from a BCC structure to a FCC structure. The lattice parameter increased from .288 nm to .357 nm and the hardness decreased from Hv 670 to Hv 149 respectively. The effect of composition on thermodynamic variables, microstructure and mechanical properties were analyzed.
Can Young’s Modulus of Metallic Alloys Change with Plastic Deformation?
Authors: Roca Antoni , Villuendas Aránzazu , Mejía Ignacio , Benito Josep Antonio , Llorca-Isern Nuria , Lluma Jordi , Jorba Jordi
Published: May 2014

The information in the basic references about the relation between elastic constants and particularly Young’s modulus (E) behavior and plastic deformation indicates that this parameter is constant or almost constant. At the beginning of the XX century several authors indicated that E of some metals decreased when cold deformation increased and detected reductions up to 15% in steels, aluminum, copper, brass... In the last years this behavior is taking into account during the finite-element analysis of sheet metal stamping or other plastic deformation processes. This work includes an extensive review of papers of our research team and of other authors related with the behavior of Young’s modulus during plastic deformation of some metallic alloys. This parameter can diminish up to 10% by plastic deformation (tension test) in iron, aluminum, and stainless steel (UNS S 30403) but remains practically unaltered in aluminum alloys deformed before or after aging. Results of Young’s modulus in nanostructured copper and copper alloys determined by ultrasonic technique are also presented. Additional results of Young’s modulus of UNS G10180 and UNS G10430 steels measured during loading and unloading steps in tension test are also included. High differences in the E values were detected between both steps.
Constrained Thermal Fatigue Performance of Several Cast Ferrous Alloys
Authors: Shyam Amit , Hawkins Shane , Erdman Donald , England Roger , Muralidharan Govindarajan
Published: May 2014

An experimental setup that was utilized to evaluate the constrained thermal fatigue (CTF) behavior of several cast ferrous alloys is described. The tests performed allowed the assessment of the relative performance of different materials in CTF loading. The stable hysteresis loop of the individual CTF tests further allowed the development of a unified parameter that determined the level of inelastic (plastic and creep) deformation and the CTF life under those conditions. A CTF life prediction methodology for cast ferrous alloys is outlined.
Analysis of Statistical Scatter in Charpy Impact Toughness
Authors: Takashima Yasuhito , Ohata Mitsuru , Minami Fumiyoshi
Published: May 2014

Charpy impact toughness values show large statistical scatter, particularly in the ductile-to-brittle transition temperature (DBTT) range. Although the statistical distribution of Charpy absorbed energy has not been clarified, critical values of the stress intensity factor, J-integral and crack-tip opening displacement (CTOD) at brittle fracture generally show the Weibull distribution with two or three parameters.
This study proposes a brittle fracture model, based on the weakest link theory, for evaluating the scatter in Charpy absorbed energy KV. The numerical results show that the amplitude of the opening stress fields ahead of the V-notch at varying amounts of KV are uniquely characterized as the square of the applied load. With these numerical results, the Weibull shape parameter of the statistical distribution of KV is almost equal to 2.
The proposed statistical model is verified through experimental results. It is found that the statistical distribution of KV is characterized by a two-parameter Weibull distribution with the shape parameter of 2 under the condition of pure brittle fracture.
Magnetic Properties of Off-Stoichiometric Ni-X-In (X=Mn, Fe and Co) Magnetic Shape Memory Alloys by First-Principles Calculations
Authors: Bai Jing , Raulot Jean M. , Zhang Yu Dong , Esling Claude , Zhao Xiang , Zuo Liang
Published: May 2014

The magnetic properties of the off-stoichiometric Ni2XIn (X=Mn, Fe, Co) are systematically investigated by means of the first–principles calculations within the framework of the density functional theory (DFT) using the Vienna ab initio software package (VASP). The magnitude of the variation in the Ni moments is much larger than that of Mn in the defective Ni2XIn. The value of the Ni magnetic moment sensitively depends on the distance between Ni and X.
Microstructure, Properties and Design of Direct Quenched Structural Steels
Authors: Suikkanen Pasi , Kömi J.I.
Published: May 2014

Direct quenching (DQ) is one of the latest process routes in production of ultra-high strength, high performance steels and Ruukki one of the pioneering companies in the utilization of direct quenching. Ruukki has applied direct quenching for the production of ultra-high-strength structural steels in the form of hot-rolled strip and plate. The paper briefly summarizes the physical metallurgy fundamental of direct steels and shows some selected examples of the microstructures and properties of steels produced by direct quenching. In addition, a brief review on the usability properties and design rules of ultra-high strength structural steels is made.
Amorphousization and Superconducting Property for Zr-Nb Based Alloy
Authors: Okai Daisuke , Mori Kentaro , Motoyama Gaku , Kimura Hisamichi , Kato Hidemi
Published: May 2014

The amorphousization of Zr65Nb35 alloy was performed. The Zr-Nb based alloys contained Al and Co elements were fabricated by arc-melting and melt-spinning methods. The superconducting property of the Zr(65-x)Nb35-xAlx (x = 0~15 at%) and Zr(65-x)Nb20Al15Cox alloys (x = 3~10 at%) was investigated by magnetic susceptibility measurements. The Zr(65-x)Nb20Al15Cox metallic glasses (x = 6~10 at%) with superconducting nanocrystalline particles dispersed in an amorphous matrix exhibited a superconductivity below about 3.5 K. The addition of Co element led drastically to the amorphousization of the superconducting Zr65Nb20Al15 alloy.
Recent Developments in the Field of Shape Memory Epoxy Foams
Authors: Santo Loredana
Published: May 2014

Shape memory epoxy foams are a new class of materials for aerospace applications as light actuators, structural parts with reduced size during transport, and expandable/deployable structures. They were tested in an experiment onboard of the International Space Station in May 2011 (Shuttle Mission STS 134) and in April 2013, on board the BION-M1 capsule through the Soyuz-2 launch vehicle, with the aim to study the behavior in microgravity for future applications.
The experiments were performed by an autonomous device which was in turn composed of control and heating system, battery pack and data acquisition system.
Micro-gravity does not affect the ability of the foams to recover their shape but it poses limits for the heating system design because of the difference in heat transfer on earth and on orbit. This could be very significant for the behaviour of complex multi-functional structures in which shape memory epoxy foams are integrated.
In this work, the main results of the experiments in microgravity are discussed and some results of tests on ground are shown in order to evaluate new possible developments in the field.
Effect of Warm-Rolling on the Formation of Microstructure and Microtexture of the Constituent Phases in a Duplex Steel
Authors: Pinaki Prasad Bhattacharjee , Mohammed Zaid Ahmed
Published: May 2014

The effect of warm-rolling on the evolution of microstructure and microtexture was investigated in a duplex steel. For this purpose annealed duplex steel plates were cold and warm-rolled up to 90% reduction in thickness at room temperature and at 625°C, respectively. The austenite volume fraction decreased consistently during cold-rolling indicating that austenite was not stable during cold-rolling. In contrast, austenite was found to be very stable during warm-rolling at 625°C. Development of an ultrafine lamellar deformation structure with alternate arrangement of the ferrite and austenite bands could be observed during warm-rolling. A strong pure metal or copper type texture was observed in the austenite in the warm-rolled material in contrast to brass texture developed during cold-rolling. Development of RD (RD//<110>) fiber and ND-fiber (ND//<111>) was observed in ferrite during both cold and warm-rolling. However, the strength of the RD-fiber was much higher as compared to the ND-fiber in ferrite in cold-rolled DSS as compared to the ferrite in warm-rolled DSS.