bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Comprehension of Mechanical, Thermal and Chemical Evolution of Exhaust Gases after Treatment Catalysts
Authors: Adamowska Małgorzata , Haddad Oriana , Leguillon Dominique , da Costa Patrick
Published: May 2014

The stricter environmental regulations impose a drastic reduction of vehicles emissions and a longer durability of the automotive catalyst. The studies of the catalyst evolution in real conditions are very expensive. It is interesting to elaborate an ageing process to well simulate the real conditions of the automotive catalyst ageing at the laboratory scale. Thermal, chemical and mechanical effects can cause degradations of the catalytic performances. Thermal ageing is the result of high temperature that surges in the catalytic converters. Chemical ageing is due to phosphorus, zinc, magnesium, calcium or sulfur originating from either engine oil additives or fuel contaminants. Mechanical ageing (cracks and detachment) is the consequence of thermal and chemical ageing (thermal and textural stresses). Understanding the formation of crack patterns and spalling of thin films is challenging in fracture mechanics. The need for two conditions, one involving energy and the other one stresses, has recently been shown. The stress condition defines a threshold below which the pattern formation is inhibited. As this threshold is not reached, the energy accumulates. Then, at onset, depending on the strength and toughness of the material, the amount of energy can be sufficiently large to give rise to a more or less dense lattice of cracks. Following, after initiation, when the crack tips are close to the support, the newly created small cells tend to separate from it, thicker the film and more harmful the debonding.
Structure Controlled Nanoparticle Conjugates Synthesized by Gas-Liquid Interfacial Plasmas
Authors: Kaneko Toshiro , Takahashi Shohei , Kato Toshiaki
Published: May 2014

A periodic structure of gold nanoparticles (AuNPs) is formed by reducing a solution of gold chloride using novel plasma techniques, where a spatio-periodically generated plasma is transcribed to the AuNP structure formed on the ionic liquid (IL) surface under the strong magnetic field. In addition, it is found that a ring-shaped AuNP structure is formed corresponding to the shape of a ring electrode inserted into the plasma, where the AuNPs are synthesized at the position without plasma irradiation due to the shielding by the ring electrode. On the other hand, the periodic structure of the AuNPs are synthesized on the carbon nanotubes (CNTs) working as a template, where the controlled ion irradiation to the IL including functional groups can realize the distance-controlled synthesis of the AuNPs by dissociation of the IL and the functionalization of the CNTs by the dissociated carboxyl and amino groups. Furthermore, DNA is used as the functional group which connects the AuNPs to the CNTs. The mono-dispersed and high-density AuNPs are synthesized on the CNTs in the same way as the carboxyl and amino groups.
Plasma Synthesis of Silicon Nanocrystals: Application to Organic/Inorganic Photovoltaics through Solution Processing
Authors: Nozaki Tomohiro , Ding Yi , Gresback Ryan
Published: May 2014

Silicon nanocrystals (SiNCs) have unique optical and electronic properties that are advantageous for semiconductor device applications and here their application to solar cell is presented. Free-standing, narrow size distribution SiNCs were synthesized by non-thermal plasma using silicon tetrachloride (SiCl4) successfully. Blended solution of as-produced SiNCs and P3HT, or Poly(3-hexylthiophene-2,5-diyl), was spin-casted to form bulk heterojunction solar cell devices. As the weight fraction of SiNCs increased up to 50 wt%, the short circuit current and the power conversion efficiency dramatically increased, while the open circuit voltage and the fill factor do not change significantly. The improved performance is attributable to increased probability of exciton dissociation at acceptor SiNCs and donor P3HT interface.
Formation of Self-Organized Pore Arrays on Metallic Substrates by Anodization and their Applications
Authors: Tsuchiya Hiroaki
Published: May 2014

The present work examines pore formation on type 316 stainless steel, Inconel 600 alloy and Co-Cr alloy. Ordered pore arrays are formed on the metallic substrates by electrochemical treatments in organic solvents containing perchlorate ions under optimized conditions. It is revealed that the key to form pore arrays is to control electrolyte composition. The formation of ordered pore arrays on stainless steel can be useful as the surface modification of the metallic biomaterial as the presence of pore arrays on stainless steel can enhance biocompatibility.
Development of Nanoalloy Catalysts for Realization of Carbon-Neutral Energy Cycles
Authors: Yamauchi Miho , Heima Minako , Sadakiyo Masaaki
Published: May 2014

Increase of CO2 concentration in the atmosphere is one of reasons for the global warming. Development of energy circulation systems, which do not emit CO2 in the atmosphere, is an emergent issue for present-generation scientists [1]. As an answer, we have proposed a new type of energy circulation system, namely, carbon-neutral energy (CN) cycle. With a practical application in mind, three limitations are imposed on the CN cycle; (1) no CO2 emissions, (2) utilization of liquid fuels and (3) minimizing the use of precious metal catalysts. In anticipation of a practical use in the near future, an alkaline fuel cell will be adapted for the CN cycle where non-platinum catalysts can work. For our purpose, electric power will be generated by partial oxidation of alcohols to carboxylic acids.[2] In view of ease in handling, fuels having a high boiling point (b.p.) are favorable for the CN cycles. To this end, glycol (EG) of which b.p. is 470 K an ideal candidate as a fuel. In this case, an oxidized product of EG can be oxalic acid. Compared to the energy obtained by the complete oxidation of EG into CO2, we can derive ca. 80 % of energy even in the partial oxidation of EG to oxalic acid, implying that the EG/oxalic cycle possibly works as an energy cycle. We herein show an example of selective EG oxidation catalysts working in alkaline conditions.
Enhanced Wettability of Cubic Boron Nitride Films by Plasma Treatment
Authors: Yang Jason Hsiao Chun , Kawakami Shinji , Teii Kungen , Matsumoto Seiichiro
Published: May 2014

The wettability of hydrogen plasma-treated cubic boron nitride (cBN) films is studied. The films are prepared on Si substrates by inductively coupled plasma (ICP)-enhanced chemical vapor deposition, and further treated by pure hydrogen ICP and microwave plasma (MWP) separately. The surface roughness of the films and the cBN content in the films show only minor changes after the plasma treatment in any treatment condition. The contact angle of polar water and apolar 1-bromonaphthalene is reduced greatly with the ICP post-treatment, while it is reduced only moderately with the MWP post-treatment. The highly hydrophilic behavior with very low contact angles is attributed to a marked increase in the polar component of the apparent surface free energy up to 34 mJ/m2.
High Resolution Diffraction of a Superalloy during HT Processing and Mechanical Testing: Experiments and Modeling
Authors: Jacques Alain , Biskri Mohamed , Chateau-Cornu Jean Philippe , Schenk Thomas , Bastie Pierre
Published: May 2014

We present a computer inexpensive method to calculate the profile of the high resolution diffraction pattern of a single crystal superalloy. The displacement field is taken as the sum of the individual fields of cuboidal inclusions with uniform eigenstrains. Early simulations are compared to experimental data.
Quantitative Investigation on Nano-Scale Precipitates in an Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr Alloy under Various Aging Tempers
Authors: Xiong Bai Qing , Liu Dong Mei , Li Zhi Hui , Li Xi Wu , Zhang Yon Gan , Wang Feng , Liu Hong Wei
Published: May 2014

In the present study, a systematic study of nanoscale precipitates in an Al-7.5Zn-1.7Mg-1.4Cu-0.12Zr alloy have been carried out for various typical aging tempers, including T6, T76, T74, T73 and RRA treatments, by combining synchrotron-based small-angle x-ray scattering (SAXS) and transmission electron microscopy (TEM) techniques. Based on the TEM observations, quantitative and statistical structural information, including precipitate size, volume fraction, number density and inter-precipitate distance have been extracted from SAXS data through model fitting. The results show that the T6 peak-aged alloy with the smallest precipitate size has the highest number density and lowest volume fraction of precipitates. Under two-step T7X over-aged tempers, with the deepen of aging degree, the precipitate size, volume fraction and inter-precipitate distance increases, but the number density decreases. The size distribution of precipitates for the RRA-treated alloy is in between that of T6 and T76. The results also show that as the degree of over-aging deepens, the precipitate size distribution interval becomes broader.
Radiographic and Tomographic Neutron Bragg Imaging for Quantitative Visualization of Wide Area Crystalline Structural Information
Authors: Sato Hirotaka , Shiota Yoshinori , Todaka Yoshikazu , Shinohara Takenao , Kamiyama Takashi , Ohnuma Masato , Furusaka Michihiro , Kiyanagi Yoshiaki
Published: May 2014

Recent status of the technical development of the Bragg-edge neutron transmission imaging and its application to material science is presented. The neutron Bragg imaging has the advantages in measuring large area with reasonable spatial resolution, and it is a non-destructive method capable of looking inside a bulk material. Therefore, various information that are quite different from EBSD, synchrotron microtomography and X-ray/neutron scattering can be obtained by this method. We carried out quantitative imaging to obtain crystalline microstructural information in ultralow-carbon steels that received the high pressure torsion (HPT). The real-space distributions of texture and grain/crystallite size of HPTed steels of four torsion numbers were quantitatively visualized at once. As a result, we could deduce unique distributions of microstructural information depending on each torsion number, and correlated them with real-space distributions of the Vickers hardness. We also successfully developed a versatile strain tomography technique that can obtain tensor values for strain although traditional CT techniques can deal with only scalar values. The new CT algorithm, the tensor CT method, is based on our original algorithm called FBP-EM. The strain tensor tomography using FBP-EM was successfully applied for the experimental measured result obtained with the VAMAS neutron strain analysis international standard sample.
Solidification of Immiscible Alloys and Convective Effect
Authors: Zhao Jiu Zhou , Jiang Hong Xiang
Published: May 2014

A model describing the microstructure formation in a directionally solidified immiscible alloy under the convective effect is presented. The microstructure evolution in a directionally solidified Al-Pb alloy is investigated. It is demonstrated that convective flows have great effects on the solidification of immiscible alloys. A convective flow against the solidification direction causes an increase in the nucleation rate while a convective flow along the solidification direction causes a decrease in the nucleation rate. The convective flows lead to a more uneven distribution of the minority phase droplets in the melt. It causes an increase in the size of the largest minority phase droplets and is against the obtaining of the immiscible alloys with a well dispersed microstructure.
Impact of Metallurgical Size Effects on Plasticity of Thin Metallic Materials
Authors: Hug Eric , Keller Clément , Habraken Anne Marie
Published: May 2014

Three examples involving size effects are presented with implications concerning the formability: small Ni-20wt.%Cr resistive bridges, magnetic micro-sensors performed with (Ni, Co, Fe) based alloys and copper clad aluminum thin wires. The mechanical properties are directly linked to the ratio thickness over grain size (t/d ratio) of the parts. These metallurgical considerations must be taken into account when we are concerned by the numerical simulation of the process of such components. It is shown that the simulations can correctly reproduce the softening effect linked to a decrease in thickness and in number of grains across the thickness: the quality of the final shape strongly depends on the number of grains across the thickness. Finally the effect of a moderate increase in temperature on these results will be briefly reported.
Microstructural Barriers against Fatigue Crack Growth
Authors: Knorr Alain Franz , Marx Michael
Published: May 2014

Fatigue induced fracture is the number one reason for failure of technical systems. However, in the stage of small crack growth grain or phase boundaries lead to a fluctuating crack propagation rate near the obstacle. Sometimes the cracks stop completely for a large number of cycles resulting in an additional number of life time cycles. However, so far it is not clear, what actually determines the resistance of a grain boundary against fatigue cracks. Therefore we developed a systematic experimental technique based on in-situ imaging in the scanning electron microscope and focused ion beam (FIB) crack initiation which gives detailed information on the interaction of short fatigue cracks with microstructural elements. We investigated the mechanisms of crack transmission in the neighbouring grain on the microscopic scale and identified different useful aspects of the interaction between microcracks and microstructural barriers. The 3D-tomographs revealed by serial sectioning an FIB give information about the transition process from one grain to the neighbouring one. The result is a purely geometrical consideration leading to a quantitative description of the blocking effect of grain boundaries on short fatigue crack growth. The results include useful aspects for fatigue life calculation and to make materials more fatigue resistant.
Evaluation of Fatigue Damage by Diffraction Contrast Tomography Using Synchrotron Radiation
Authors: Shiozawa Daiki , Nakai Yoshikazu , Miura Ryotaro , Matsuda Shota
Published: May 2014

The three dimensional grain mapping technique for polycrystalline material, which is called X-ray diffraction contrast tomography (DCT) has proposed. In the present study, the measurement of DCT was conducted in SPring-8, which is the brightest synchrotron radiation facility in Japan, and the condition of measurement and data procedure are discussed. Developed technique was applied to aluminium alloy and stainless steel. The shape and location of grain could be determined by the developed three-dimensional mapping technique using the apparatus in a bending beam line of SPring-8. To evaluate plastic deformation, the grain orientation spreads of individual grains were measured. The grain orientation spread is caused by the mosaicity, which relates to the dislocation structure in a grain. The grain orientation spread was found to increase with increasing plastic strain. Fatigue damage also could be evaluated by the grain orientation spread in the DCT measurement.
Image Processing Characterization of Microstructures of Al-Si Casting Alloy
Authors: Sugio Kenjiro , Furukawa Shota , Kengai Taruho , Tabata Junji , Sasaki Gen
Published: May 2014

Mean free path of dislocation motion have a significant effect on mechanical properties because dislocation motion is blocked by eutectics and intermetallics in Al-Si casting alloys. In this study, we proposed a statistical method to evaluate mean free path of dislocation motion by using image processing, and investigated relation between the measured mean free path and mechanical properties of Al-Si casting alloys.
A Study of Solid State Bonding Strength of Nonferrous Metals by Using Metal Salt Generation Bonding Method
Authors: Koyama Shinji
Published: May 2014

In recent years, an enormous pressure was put on the need to design and develop products that are compliant with the stringent environmental regulations set up various countries. Among the problems that need to be addressed is the need to design and develop environmentally friendly products that are energy efficient and easy to recycle. In this study, the effect of metal salt generation processing on the tensile strength of the bonded interface of Al/Al and Al/Cu was investigated by SEM observations of interfacial microstructures and fractured surfaces. Aluminum surfaces were modified by boiling in 5% aqueous solution of NaOH for 30 s and 98% formic acid for 60 s. Copper surface were modified by boiling 98% formic acid for 60 s. Solid-state bonding was performed at bonding temperature of 673 ~ 813 K and under a pressure of 6 MPa ( bonding time of 1.8 ks). Using metal salt generation bonding technique, the bonded joint is able to reach 0.2% proof stress at lower bonding temperature and with less deformation.
Progress on High Pressure Pneumatic Forming and Warm Hydroforming of Titanium and Magnesium Alloy Tubular Components
Authors: Liu Gang , Wu Yong , Wang Jian Long , Zhang Wen Da
Published: May 2014

Complex structural tubular components of Titanium and Magnesium alloy can be obtained at a certain temperature by high pressure pneumatic forming (HPPF) with gas medium or warm hydroforming with pressurized liquid medium. At 800°C, through experimental research on HPPF of TA18 Ti-alloy tube with expansion ratio of 50%, the influence of axial feeding on thickness distribution of the workpiece was studied. Using reasonable loading curve, the component with large ratio can be formed with a small thinning ratio as 13% with total axial feeding amount of 40mm.
At 850°C, HPPF experiments of TA18 Ti-alloy component with square section were carried out. The influence of gas pressure on thickness distribution and corner filling process were analyzed. The larger the pressure, the sooner the displacement changes at the corner, and the shorter corner filling term. At pressure of 30 MPa, small corner with the relative corner radius of 2.0 can be obtained within 168s. For Mg-alloy tubular part, warm hydroforming with non-uniform temperature field was studied. By using reasonable axial temperature field and loading path, the maximum thinning ratio of Mg-alloy tubular component with expansion ratio of 35% was reduced from 21.6% to 11.6%.
Bimodal and Monomodal Diamond Particle Effect on the Thermal Conductivity of Diamond Particle Dispersed Al Matrix Composite Produced by SPS
Authors: Mizuuchi Kiyoshi , Inoue Kanryu , Agari Yasuyuki , Sugioka M. , Tanaka M. , Takeuchi T. , Tani J. , Kawahara M. , Makino Y. , Ito Mikio
Published: May 2014

Diamond-particle-dispersed aluminum (Al) matrix composites consisting of monomodal and bimodal diamond particles were fabricated in spark plasma sintering process, where the mixture of diamond, pure Al and Al-5mass% Si alloy powders were consolidated in liquid and solid co-existent state. Microstructures and thermal properties of the composites fabricated in such a unique way were investigated and the bimodal and monomodal diamond particle effect was evaluated on the thermal properties of the composites. The composites can be well consolidated in a temperature range between 773 K and 878 K and scanning electron microscopy detects no reaction product at the interface between the diamond particle and the Al matrix. Relative packing density of the composite containing monomodal diamond particles decreased from 99.1% to 87.4% with increasing volume fraction of diamond between 50% and 60%, whereas that of the composite containing bimodal diamond particles was higher than 99% in a volume fraction of diamond up to 65%. The thermal conductivity of the composite containing bimodal diamond particles was higher than that of the composite containing monomodal diamond particles in a volume fraction of diamond higher than 60% and the thermal conductivity of the composite containing 70 vol.% bimodal diamond particles was 578 W/mK at R.T..
Mechanical and Electrical Properties of Carbon Nanofiber Dispersed Ti Composite Formed by Compression Shearing Method at Room Temperature
Authors: Nakayama Noboru , Horita M. , Miki H. , Takagi T. , Takeishi H.
Published: May 2014

The materials used for fuel cell separators require a bending strength of more than 70 MPa. Therefore, the contact resistance is required to be 10 mΩ∙cm2, respectively. In the present study, vapor grown carbon nanofibers (VGCF) were added to Ti composite using the compression shearing method at room temperature. The mechanical properties of the compacted powder were then measured. The microstructure of the Ti/VGCF composite material was Ti with dispersed VGCF (not alloyed). In addition, the bending strength of all Ti/VGCF composites was more than 800 MPa, and the bending strength of 0-1 vol% VGCF composites was twice as much as that for Ti rolled material (ASTM grade 2). Ti/VGCF thin plates also exhibited excellent electrical property. The contact resistance of 5 vol% VGCF was found to be three times smaller than that of Ti rolled material. These properties make the Ti/VGCF composite material suitable as a separator material.
Development of Nickel Based Superalloys for Advanced Turbine Engines
Authors: Nowotnik Andrzej , Kubiak Krzysztof , Sieniawski Jan , Rokicki Paweł , Pędrak Paweł , Mrówka-Nowotnik Grazyna
Published: May 2014

Superalloys have been developed for specific, dedicated properties and applications. One of the main application for this material is advanced, high-performance aircraft engines elements. Turbine engine creates harsh environments for materials due to the high operating temperature and stress level. Hence, as described in this article, many alloys used in the turbine section of these engines are very complex and highly optimized. This article provides an overview of structural changes that occur during the aging process of wrought and cast alloys and provides insight into the use of precipitated particles to achieve desired structures. Example will focus on alloy Inconel 718 and CMSX-4. Functional properties of these alloys can be achieved by choosing proper heat treatment parameters to obtain required rate between secondary phases. The paper also attempts to determine structural perfection and changes of crystallographic orientation along the axis of growth of single crystal nickel superalloys cast using X-ray topography and Laue diffraction method. Single crystal bars and turbine blades were manufactured in VIM furnace using the Bridgeman method. Withdrawing rates typical for CMSX-4 superalloy were used. It has been found that with increasing withdrawing rate the nature of distribution along the axis of growth of the angle of [001] direction deviation from the axis of single crystal blades growth had changed. The change of the withdrawing rate results also in the rotation of γ’ phase in the form of cubes against the axis of single crystal blades growth.
Influence of New System Nano-Inhibitors on the Abnormal Grain Growth with Goss Crystallographic Orientation of Silicon Steels
Authors: Kováč František , Petryshynets Ivan , Buršík Jiří , Sopko Martin
Published: May 2014

In the present work some new approaches have proposed for the grain oriented steel fabrication. This approach employs the new system of VC nanoprecipitates in the combination with dynamic continuous annealing for secondary recrystallization. The new system of VC inhibitors and dynamic annealing was applied to the grain oriented steel in order to obtain abnormal grain growth with Goss crystallographic orientation and considerably reduces the preparation time as the whole process lasts only several minutes. The EBSD analysis shown that suggested procedure led to evolution of the sufficiently strong {110}<001> Goss texture, which is comparable to that obtained in the conventionally treated GO steels. Moreover, the steels treated by this new method have the comparable final magnetic properties as the materials passed the conventional long – time heat treatment.
Effect of Annealing on Structure and Mechanical Behavior of an AA2139 Alloy
Authors: Tagirov Damir , Zhemchuzhnikova Daria , Gazizov Marat , Kaibyshev Rustam
Published: May 2014

An AA2139 alloy with a chemical composition of Al–4.35Cu-0.46%Mg–0.63Ag-0.36Mn–0.12Ti (in wt.%) and an initial grain size of about 155 μm was subjected to annealing at 430°C for 3 h followed by furnace cooling. This treatment resulted in the formation of a dispersion of coarse particles having essentially plate-like shape. The over-aged alloy exhibits lower flow stress and high ductility in comparison with initial material in the temperature interval 20-450°C. Examination of microstructural evolution during high-temperature deformation showed localization of plastic flow in vicinity of coarse particles. Over-aging leads to transition from ductile-brittle fracture to ductile and very homogeneous ductile fracture at room temperature.
Deformation Texture and Microstructure Evolution in Nickel and Nickel-Cobalt Alloys
Authors: Madhavan R. , Ray Ranjit K. , Suwas Satyam
Published: May 2014

Rolling texture evolution of pure nickel, and nickel – cobalt alloys containing 20wt.%, 40wt.%, 60wt.% cobalt content has been studied to very large true strain (ε ~ 4). The texture evolution in pure nickel and Ni-20Co was very similar, and resulted in typical Cu-type rolling texture. Microstructural analyses showed that the deformation was mostly slip dominated up to 95% beyond which it shear bands. Deformation twinning was a major deformation mechanism up to 50% reduction, and at higher strains, microstructure showed extensive shear banding. The evolution of final Goss texture in low SFE Ni-Co alloys could be explained based on the twin fraction and shear band volumes which showed grains preferably oriented towards Goss.
Texture Formation in Flow Formed Ferritic Steel Tubes and the Influence of the Process Parameters
Authors: Tsivoulas Dimitrios , Timar Gabor , Tuffs Martin , da Fonseca Joao Quinta , Preuss Michael
Published: May 2014

The crystallographic textures of flow formed parts are of great scientific interest as they result from a complex deformation mode that comprises strain components in the axial and hoop directions. In general they resemble those of the rolling type but with slight differences. The present paper analyses the effects of certain process parameters, such as roller contact angle, feed rate, and preform hardness, since these are crucial in defining the forces acting in each principal direction of the component. Additionally, the development of a texture gradient through the wall thickness is also discussed. Texture predictions from a crystal plasticity finite-element model were also employed to support the experimental data and interpret the deformation mechanisms. Finally, the diverse nature of the flow formed textures is verified by annealing treatments at 700°C, which yields the typical gamma-fibre encountered in rolled ferritic steels upon recrystallisation in conjunction with the strengthening of the (113)[1-10] component.
Microstructural Evolution and Grain Refinement in a Cu-Zr Alloy Processed by High-Pressure Torsion
Authors: Wongsa-Ngam Jittraporn , Langdon Terence
Published: May 2014

A copper alloy, Cu-0.1% Zr, was processed at room temperature by high-pressure torsion (HPT) in order to evaluate the microstructural evolution and grain refinement mechanism. Transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) techniques were employed to measure the grain morphology, grain size distributions and the distribution of the misorientation angles. The results demonstrate that this processing procedure has a potential for producing an ultrafine-grain structure containing reasonably equiaxed grain with high-angle boundary misorientations. The grain refinement mechanism is primarily governed by dislocation activities.
Microstructure Development and Superplasticity in a Zn-22% Al Eutectoid Alloy Processed by Severe Plastic Deformation
Authors: Kawasaki Megumi , Langdon Terence
Published: May 2014

Severe plastic deformation (SPD) is an attractive processing method for refining microstructures to have ultrafine grain sizes within the submicrometer or even the nanometer levels. In SPD, the most promising techniques are equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). A conventional superplastic Zn-22% Al eutectoid alloy was processed by ECAP and HPT. Experiments were conducted to demonstrate the evolution of hardness and microstructure and the enhancement of superplastic properties of the Zn-Al alloy after processing by the SPD techniques. In addition, flow mechanisms of the Zn-22% Al alloy are discussed by utilizing a deformation mechanism map.
Micro Hole Piercing for Ultra Fine Grained Steel
Authors: Komatsu Takafumi , Kobayashi Hitoshi , Torizuka Shiro , Nagayama Shinichi
Published: May 2014

Ultra fine grained steels have been developed by many researchers. However, the study of influence on processes and product functions from different grain size are limited because the size of bulk material was small for these products. Authors have developed the production process of thin ultra fine grained stainless steel coil, and the effects are able to be clarified. This paper will firstly report the influence on micro hole piercing by comparing different grain size materials. Secondly, orifices are produced from these materials, and the liquid flow volume is measured as the functional effect of different grain size. The effects of grain size differences were discussed with observing the hole conditions and measuring flow volume. The effects of reduction of the grain size were summarized as follows: (1) Accurate small hole is produced when ultra fine grained stainless steel is employed. (2) Product functional improvement is possible, and the phenomena are useful for liquid control devices.
Two-Scale Finite Element Analysis of Equaled Channeling Angular Extrusion of Polycrystalline Metal
Authors: Watanabe Ikumu
Published: May 2014

A two-scale finite element analysis method based on a micro-macro decoupled scheme is applied to an equaled channeling angular extrusion. At first, the macro-scale finite element analysis for one process of an equaled channeling angular extrusion is carried out with a non-liner explicit method to handle the contact and friction between die and bullet. Using the deformation history at a macroscopic material point in this process, the micro-scale finite element analysis is conducted for the multiple processes with a single crystal plasticity and a nonlinear implicit method. As the results, the deformation process of the polycrystalline aggregate during the equaled channeling angular extrusion is numerically reproduced.
Micro-Tensile Behavior at a High Temperature in an AZ31 Magnesium Alloy Processed by ECAP
Authors: Xu Jie , Guo Bin , Shan De Bin , Langdon Terence
Published: May 2014

A magnesium AZ31 alloy was processed by ECAP at a temperature of 473 K using a die with a channel of 110o. The results show that the grain size was reduced from 5.4 μm to ~1.0 μm. Micro-tensile tests of the AZ31 alloy were conducted using as-received and ECAP-processed AZ31 alloy at a temperature of 473 K. The ductility of the AZ31 alloy can be improved significantly after ECAP processing at high temperature, which demonstrates a potential application in micro-forming technology for the UFG AZ31 alloy.
Optimisation of Diffusion Bonding Parameters of Ti Alloys through the Structure and Surface Conditions
Authors: Yakushina Evgenia , Reshetov Aleksey , Rosochowski Andrzej
Published: May 2014

Diffusion bonding of Ti-6Al-4V titanium alloy in the coarse grained and ultrafine grained state was performed. The effect of initial structure and surface condition, as well as temperature and time, on the quality of joints was established. It is shown that, due to low-temperature superplasticity and high diffusion rate, samples with ultrafine grained structure demonstrate better bondability than coarse grained samples
Aspects of Thermomechanical Processing of 3rd Generation Advanced High Strength Steels
Authors: Poliak Evgueni I. , Bhattacharya Debanshu
Published: May 2014

The production of advanced high strength steels (AHSS) has been rapidly expanding in recent years as these steels allow for considerable reduction in weight and enhancement of car safety due to the unique combination of high strength, toughness and formability. Driven by growing demand for sheet AHSS products from carmakers, steel producers are currently developing AHSS of the so called 3rd Generation to further facilitate weight reduction of critical safety parts while ensuring crash worthiness and high absorbed energy. Such steels not only possess tensile strength above 1000 MPa but also are being designed for exceedingly high formability: high elongation, bendability, hole expansion and strain hardening. These enhanced properties are to be achieved in final operations of continuous annealing and/or galvanizing. However, due to complicated alloy designs of 3G AHSS the role of each manufacturing stage becomes progressively significant due to its impact on the final microstructure. Therefore, hot strip rolling gains increasing importance as one of the most critical stages responsible for producing the microstructure optimal for achieving the final properties of the sheet products without impairing downstream operations. In other words, hot rolling of AHSS has to be viewed as thermomechanical processing.
Effect of Processing Conditions on the Microstructure Development during Constrained Groove Pressing of Aluminium
Authors: Zrník Jozef , Kraus Libor , Cieslar Miroslav , Sláma Peter
Published: May 2014

In this study, the relationship between the structure and properties of commercial purityaluminium (AW-1199) was investigated by applying constrained groove pressing (CGP) method.The refinement of the coarse grain aluminium microstructure to submicrocrystalline size by largeplastic strain at room temperature defined. The impact of various strains upon microstructurechanges is investigated using transmission electron microscopy (TEM) and electron back scatterdiffraction (EBSD). A mixture of subgrains produced by grains subdivision and polygonizedsubgrains formed locally due to dynamic recovery was found in the deformed aluminium. Thetensile properties and resulting hardness are related to microstructural evolution induced by CGP. Asubstantial impact of straining upon the increasing in tensile strength was observed after the firstpass. Further strain increase had an insignificant effect on tensile strength but was accompanied byductility loss. The post deformation annealing effect was then explored with aim to increase theductility. The results indicate that changes in strength and ductility may be related to formation of abimodal structure.
Corrosion Characterization of Magnesium Alloys – The Role of Process Parameters
Authors: Ben Hamu Guy
Published: May 2014

The present work presents a comparative study of FSW die cast AM50 Mg alloy. The main focus is the effect of the FSW metallurgy on the corrosion behavior of the alloy. AC and DC polarization tests were carried out on the FSW Mg alloys. The microstructure was examined using electron microscopy (SEM).
Compressive Characteristics of AZ91 Containing Sn Alloy with the Microstructure
Authors: Choi Tae Young , Jung Hyun Ju , Kim Dae Hwan , Lim Su Gun
Published: May 2014

The characteristics of AZ91 containing Sn alloy were investigated to understand the compressive behavior with the microstructure of the alloy in elevated temperature state. To change the microstructure, the alloys used for this study were fabricated by the permanent mould casting and cooling slope casting, respectively. The compression test of AZ91 containing Sn alloys was carried out at temperatures from R.T to 400°C and at strain rates from 1.67x10-5 to 1.67x10-3/s. Besides, in order to investigate the compressive characteristics of the alloys in the elevated temperature state, this alloys after compression test were performed by optical (OM) and results show that the compressive deformation behavior of AZ91 containing Sn alloy was affected by strain rate and deformation temperature as well as its microstructure under hot forming conditions. In the processing windows for the soundness evolution of the specimen in the compression process, the Mg alloy with a dendrite phase (by permanent mold casting) was narrower than that of the Mg alloy with a globular and fine phase (by cooling slope method).
Microstructure and Mechanical Property in Cast AZ91 Magnesium Alloy with Y Addition
Authors: Sakamoto Tatsuaki , Sun Shu Chen , Matsumoto Takuya , Nakai Kiyomichi , Kobayashi Sengo , Matsuda Seiji , Tang Wei , Tu Gan Feng
Published: May 2014

Microstructures and Vickers microhardness in AZ91 magnesium alloys without and with 1mass%Y addition fabricated by casting were investigated. Vickers microhardness increases with adding 1%Y. Microstructure in AZ91 without Y addition was analyzed to contain mainly α-Mg and Mg17Al12 by X-ray diffraction. Microstructural observations with optical, scanning and transmission electron microscopes show that microstructure consists of α-Mg dendrite, non-equilibrium eutectic Mg17Al12 and lamellar Mg17Al12. The non-equilibrium eutectic Mg17Al12 exists between α-Mg dendrites. The lamellar Mg17Al12 forms near the edge of the α-Mg dendrite arm. The lamellar Mg17Al12 has Burgers orientation relationship for α-Mg matrix. It suggests that the lamellar Mg17Al12 precipitates from Al-supersaturated region within α-Mg dendrite. Addition of Y to AZ91 hardly changes dendrite arm spacing, but decreases a size of region, where longitudinal directions of primary dendrite arms are almost parallel or a single dendrite exists. Y-addition increases nucleation site for dendrite, namely makes the unidirectionally-solidified region fine, resulting in increase in hardness.
Method for the Depletion of the Basal Texture in Rolled AZ31 Magnesium Sheets
Authors: Schmidt Christian , Kawalla Rudolf
Published: May 2014

The deformation and hardening mechanisms of magnesium usually lead to a typical basal orientation of crystals during a production of sheets by forming techniques. The basal texture related anisotropic property behavior and especially the further decrease in formability at room temperature is disadvantageous and undesired for subsequent rolling and final forming processes.The objective of this work is to find methods to improve these texture-related properties and the cold forming ability of magnesium sheets. Firstly, rolling at different temperatures and pass reductions, with the goal of weakening the basal texture component in semi-finished products is investigated, based on the advantageous initial texture and microstructure of twin-roll-cast (TRC) magnesium strips. In this context, texture and microstructure development is examined after a particular multi-pass rolling and heat treatment processes. Twin-roll-cast magnesium strips of alloy AZ31, with an initial thickness of 4.5 mm, rolled to a final thickness of 1.2 mm, are used as feedstock.Secondly, a new thermo-mechanical magnesium strip treatment has been developed in order to completely disintegrate the basal texture and intentionally generate only non-basal orientations with high Schmid-factors for the easy-to-activate basal slip systems. This process, which is designed as a final strip treatment, has been investigated regarding its texture change effect on rolled 1.2 mm AZ31 sheets, which also originate from TRC feedstock.It has clearly been found that the developed rolling technology for TRC feedstock leads to a significantly reduced basal texture due to grain boundary rotation and recrystallization at those rotated regions. The application of the separately developed strip treatment effects a complete elimination of the basal texture in a large volume of the sheet. Applying both technologies on magnesium sheets results in a tremendous increase in formability at room temperature as a consequence of the altered texture.
Recovery and Recrystallization during Thermo-Mechanical Processing of Ti-6.5Al-1.5Zr-3.5Mo-0.3Si Alloy
Authors: Chen Hui Qin , Zhao Xiao Dong , Chai Yue Sheng , Cao Chun Xiao
Published: May 2014

In this investigation, microstructure evolution of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy during thermo-mechanical processing at temperatures in beta single-phase and alpha+beta two-phase fields was studied. Microstructure analyses indicate that: (1) in the beta single-phase field, dynamic recovery accompanied by geometric dynamic recrystallization at large strains takes place dominantly within elongated large prior beta grains with serrate grain boundaries during deformation at higher temperatures and lower strain rates; and discontinuous dynamic recrystallization occurs along elongated small prior beta grain boundaries during deformation at lower temperatures and higher strain rates. During discontinuous dynamic recrystallization, recrystallized grain size is a function of Zener–Hollomon parameter, and a modified Avrami recrystallized kinetic model was established. (2) In the alpha+beta two-phase field, the globularization process is a thermally activated process controlled by parameters of temperature and strain rate. A modified Avrami globularized kinetic model was established. The primary alpha grain size is a function of Z on a ln-ln scale.
Dynamic Globularization of α-Phase in Ti6Al4V Alloy during Hot Compression
Authors: Mutombo Kalenda , Siyasiya C. , Stumpf W.E.
Published: May 2014

Ti6Al4V samples were isothermally compressed using a Gleeble(TM) 1500D thermo-mechanical simulator. Differential scanning calorimetry (DSC), microstructural analyses, and thermodynamic calculations were used to investigate the sequence of transformation of β into α or vice-versa and the presence of different phases in the compressed Ti6Al4V sample. Globular alpha phase was revealed in the isothermally compressed sample in addition to martensitic and lamellar α/β structures. The transition temperature range of β into α-phase was determined using the DSC thermograms and thermodynamic calculated diagrams. The fraction of α-phase globulized increased as the strain rate decreased from 0.01s-1 to 10-3s-1, and the spheroidization of the α-phase is only possible in a specific range of deformation temperatures.
FEM Study of Superplastic-Like Forming of Ti-6Al-4V Alloy
Authors: Liu Jun , Guo Mei Ling , Tan Ming Jen , Chua Beng Wah
Published: May 2014

A superplastic-like forming (SPLF) process involving the use of hot drawing along with blow forming is studied here. The hot drawing stage helps in enhancing the formability and in fast forming the metal sheet into a hollow shape with desired amount of material draw-in. During the blow forming stage, gas pressure was applied onto the pre-formed part to complete the forming process at a targeted strain rate. Ti-6Al-4V sheets have been successfully formed by this process at 800 °C in 16 min. In this paper, finite element modeling (FEM) was used to demonstrate the effects of each stage (hot drawing and blow forming) during SPLF. A plasticity model based on tensile test data was adopted as a material model for simulation. The pressure cycle which was predicted from the simulation has been used in the process to maintain the sheet forming at an average strain rate (e.g. 10-3, 5×10-4 and 10-4 s-1. Experimental measurements, i.e. material draw-in and thickness distribution, were used to compare and validate the results from simulations. The validated simulations have shown the capability of the model to be used for the forming process. The influences of varying process parameters, such as drawing stroke, blank-holder force, friction coefficient and pressure cycle, were investigated by the simulations. It was found that the punch geometry and drawing stroke played significant roles on the thickness uniformity of the final part, from which an optimized hot-drawing system that could result in minimum thinning has been designed by FEM.
Beta-Forging of Ti6Al4V Titanium Alloy Powders Consolidated by HIP: Plastic Flow and Strain-Rate Relation
Authors: Testani Claudio , Squillace Antonino , Fratini Livan
Published: May 2014

Ti6Al4V is probably the best known and studied titanium alloy, not only for aerospace applications. Nevertheless the deformation behavior still represents a challenge if any modification in the deformation process is required or introduced. This work deals with deformation behavior description of Ti6Al4V HIPped powders during high temperature deformation tests carried on in the Beta-region. Laboratory compression and tensile tests have been coupled with relaxation tests in order to achieve robust data about strain rate sensibility m-coefficient and activation energy Q. These results have been fitted for the assessment of a more general exponential deformation law. The final result is a “Dorn model” that takes into account and compare all the results from the three different laboratory techniques: compression, tensile and relaxation with a statistical correlation coefficient Rd2=0,78. The deformation tests have been carried out at temperatures ranging from 1173 K up to 1373 K and strain rate from 0,01 s-1 up to about 1 s-1, trying to describe the high temperature complex shape forging operations. The final results has been used and are in use for modeling the forging precursors and dies-shapes to optimize industrial small scale forging tests.
Microstructural and Mechanical Properties of the Intercritically Reheated Coarse Grained Heat Affected Zone (ICCGHAZ) of an API 5L X80 Pipeline Steel
Authors: Andia J.L.M. , de Souza Luís Felipe Guimarães , Bott Ivani de Souza
Published: May 2014

The weld thermal cycle, depending on the welding process and steel composition can reduce the toughness of the HAZ when compared with the base metal. In the intercritically reheated coarse grained HAZ (ICCGHAZ) region, microstructural transformations from coarse austenite to bainite or martensite are liable to occur. Reheating into the dual phase field temperature and subsequent cooling can lead to the formation of “microphases” commonly referred to Martensite-Austenite (MA) constituent. Due to the C enrichment of the austenite, this region is regarded as local brittle zones (LBZ) and degradation of HAZ toughness can be attributed to the formation of local brittle zones (LBZ) at the ICCGHAZ. This work will discuss the characteristics of the ICCGHAZ of two API5LX80 steels produced by thermomechanical controlled process (TMCP) without accelerated cooling using a finishing rolling temperature in the dual phase field, where the main hardening mechanisms are grain refining and precipitation. Weld thermal cycle simulation, using a Gleeble 3800®, characterised by the peak temperature (Tp) of 800oC and the cooling time from 800 to 500oC (∆t800–500) were applied in order to obtain an ICCGHAZ equivalent to a 2.5, 3 and 4kJ/mm heat input. Charpy-V tests and metallographic analysis using optical and electron microscopy were carried out to evaluate the simulated zone. The results have shown that the ICCGHAZ presented a necklace microstructure at the prior austenite grain boundaries associated with the low impact energy and the presence of the MA microconstituent.
Study of Dislocation Substructures in High-Mn Steels by Electron Channeling Contrast Imaging
Authors: Gutierrez-Urrutia Iván , Raabe Dierk
Published: May 2014

We have investigated the formation of dislocation substructures in high-Mn steels by electron channeling contrast imaging in the SEM. The coupling of electron channeling contrast imaging (ECCI) with electron backscatter diffraction (EBSD) provides an efficient and fast approach to characterize dislocation substructures under controlled diffraction conditions with enhanced contrast. The dislocation substructure of high-Mn steels at intermediate strain levels is characterized by cells and cell blocks with strong crystallographic orientation dependence. We observe a significant effect of strain path on dislocation patterning. Microband formation is enabled under shearing conditions. We explain this effect on terms of Schmid’s law.