bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical-Hydrothermal Synthesis of Zr-Containing Titanium Oxide Film on CP-Ti
Authors: Ueda Masato , Ikeda Masahiko
Published: May 2014

Titanium and its alloys have been employed in bone plates/screws, which must be removed after recovery. Conduction of bone occurs on the surface of Ti alloys that reside in the body for a long period. This can lead to re-fracture of cured bone in removal operations. On the other hand, bone has been reported not to be formed on the surface of Zr alloys. The purpose of this study was to synthesize Zr-containing TiO2 film on commercial purity titanium (CP-Ti) by chemical-hydrothermal treatment. In addition, apatite formation on the films in Hanks’ solution and bone conduction in the tibiae of rats were also investigated. CP-Ti substrates were chemically treated with H2O2/HNO3 aqueous solutions at 353 K for 20 min. The substrates were hydrothermally treated with ZrOCl2/NH3/hydroxy acid aqueous solutions in a Teflon-lined autoclave at 453 K for 12 h. The hydroxy acid was selected to be C3H6O3 (lactic acid), C4H6O6 (tartaric acid) or C6H8O7 (citric acid). In the hydrothermal treatment without hydroxy acid, the surface product was anatase-type TiO2. In contrast, when hydroxy acid was added the surface of Ti was covered homogeneously with a Zr-containing TiO2 film. Some of the Zr (OH)4 sol in the solution is thought to have dissolved into the solution by coordinate bonding with hydroxy acid carboxyl groups, leading to incorporation of Zr as ZrO2 into the TiO2. The product films suppressed the apatite precipitation in the Hanks’ solution soaking. In animal test, the small amount of ZrO2 effectively suppressed the bone conduction.
Interfacial Reactions during Explosive Bonding
Authors: Paul Henryk
Published: May 2014

The layers near the interface of explosively welded plates were investigated by means of microscopic observations, mostly with the use of transmission electron microscopy (and Focus Ion Beam technique for the thin foils preparation) equipped with energy dispersive spectrometry. The metal compositions based on steels and Ti, Zr, Ta or Cu, were analyzed. The study was focused on the identification of the intermetallic phases inside the melted zones, the possible interdiffusion between the bonded metals and the changes in the dislocation structure.
Structure of Nanocomposites Based on Carbon Nanotubes Decorated with Platinum Nanoparticles
Authors: Dobrzańska-Danikiewicz Anna Danuta , Pawlyta Mirosława , Łukowiec Dariusz
Published: May 2014

A structure and morphology of the fabricated nanocomposite materials composed of carbon nanotubes and platinum nanoparticles is reported in the paper. High quality CNTs obtained in the CVD process with a long of 100-200 mm and diameter of 10-20 nm were used in the research. Raw CNTs did not contain metallic impurities or amorphous carbon deposits. An indirect method of bonding the earlier produced platinum nanoparticles to the surface of functionalised carbon nanotubes was used to produce carbon nanotubes – platinum nanoparticles system. The main aim of current research was structure and morphology investigation of obtained nanocomposite using Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM) and X-ray structure analysis (XRD).
Particle Pushing during Solidification of Metals and Alloys
Authors: Wang Meng , Han Qin You
Published: May 2014

During the solidification of a liquid containing dispersed second phase particles, particles are either rejected or engulfed by the advancing solid-liquid interface. Theories have been proposed on the mechanisms on particle pushing by a freezing front. However, the critical growth velocities predicted are much smaller than actually found experimentally. This article evaluates mechanisms on particle pushing. A specially selected alloy system, an Al-Ti-B master alloy, was chosen to evaluate particle pushing under various solidification conditions. The final distribution of the particles in ingots was examined. It is concluded that most of the particles are pushed by the dendritic solid liquid interface under cooling conditions varying a few orders of magnitude. Mechanical disturbance, such as fluid flow in the remaining liquid of the mushy zone, promotes particle pushing by the growing solid.
Keywords: Particle pushing, solidification, Aluminum alloys, and metal-matrix composites
Influence of Oxide Additions in Cu-Co-Fe Composite Powders Obtained by Mechanical Alloying
Authors: Llorca-Isern Nuria , Artieda-Guzman Cristina , Vique Jose Alberto , Roca Antoni
Published: May 2014

Nanocrystalline composite powders were prepared by mechanical alloying of pure Cu, Fe and Co as metallic major part and Al2O3 or Fe2O3 or SiO2 as ceramic reinforcement in a high-energy ball mill. Alloys of the copper-iron-cobalt system are promising for the development of new materials and applications. Cu-Fe-Co is used in different applications depending on the properties required. These can be related for example to toughness when used as rock cutting tool, to magnetic and electric properties for microelectronics or to chemical behaviour when used as catalysts in bioalcohol production industry. The objective of the present study is to contribute to understanding how and to which amount the ceramic reinforcement affects the properties for which this Cu-Fe-Co system is used as well as to envisage other less frequently uses for the composite powders. Structural and magnetic transformations occurring in the material during milling were studied with the use of X-ray diffraction, scanning quantum induction device (SQUID) and magnetic force microscopy (MFM). In mechanical alloying the transformations depend upon milling time. The results showed that milling the elemental powders of Cu-Fe-Co in the mass proportion of 50:25:25 respectively for times up to 10h leads to the progressive dissolution of Fe and Co atoms into FCC Cu and the final product of the MA process was the nanocrystalline Cu containing Fe and Co with a mean crystallite size (from coherent crystal size determination by diffraction) of 20 nm aprox. When ceramic particles are milled together with the metals (at proportions of the oxides between 1-10%) this mechanism is retarded. On the other hand, the lowest mean crystallite size is reached without ceramic particles in the milling process. However the composite powder produced in all the cases stabilized similar lowest crystallite size between 45-50 nm. Mechanically alloyed metallic-ceramic composite powder showed lower saturation magnetization than the metallic system but enhanced coercive field (significantly for hematite reinforcement). All the studied systems are intermediate ferromagnetics (Hc≈104 A/m). Milling time significantly affects the structure, composition and properties for both metallic and composite systems.
Cast Al-Based Nanocomposites Reinforced with Thermal Plasma-Synthesized Ceramic Nanoparticles
Authors: Boselli M. , Ceschini Lorella , Colombo V. , Ghedini E. , Gherardi M. , Morri A. , Rotundo F. , Sanibondi P. , Toschi S.
Published: May 2014

The present study aims at producing Al-based nanocomposites reinforced with low fractions of ceramic nanoreinforcement produced by thermal plasma, evaluating the strengthening effects induced by their addition to the widely used A356 (Al-Si-Mg) cast aluminum alloy. Nanoparticles were produced using a lab-scale RF inductively coupled thermal plasma system designed by simulation as to optimize the plasma operating conditions and reactor geometry. During the casting route, ultrasonic treatment of the melt was performed to better disperse the reinforcing particles into the matrix. Ceramic spherodized microparticles were also synthesized and micro-reinforced Al-matrix composites were produced with the same route for comparison. Microstructural characterization of the cast samples was carried out by optical and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) analysis. BET analysis was also used for powder characterization. Hardness tests were performed to assess the enhancement in mechanical properties obtained by addition of nanoparticles with respect to both the microparticle reinforced and unreinforced Al-Si-Mg matrix.
Measuring Threshold Pressure of Melt Magnesium Infiltrating into Al2O3sf Porous Preform with Fast Method
Authors: Zhou Ji Ming , Gu Xue Hua , Yang Fang , Qi Le Hua
Published: May 2014

Threshold pressure is a very important parameter for melt alloy successfully infiltrating into the porous preform. However, the precise measurement for threshold pressure is very difficult for the reason that infiltration process is undertaken very fast under extreme elevated temperature and high pressure without effective measuring devices to monitor it. A totally new measuring device was proposed and fabricated, which can be used to monitor the infiltration process “visually” and measure the threshold pressure directly at the same time. The infiltration speed can be controlled by adjusting the gas flow speed. The infiltration behavior of melt AZ91D alloy in Al2O3sf preform was researched at temperature of 800°C and pressure of 0.6 MPa. The optimized gas velocity was controlled at 25L/min. The degree of vacuum of the infiltration cavity was set 30kPa in experiments. The volume fraction of Al2O3sf was 10%. Under these conditions, the threshold pressure of melt AZ91D alloy into porous Al2O3sf preform was found to be related with vacuum degree in infiltration chamber, and it was about 30 kPa
Research Progress of a New Solid Oxide Metal-Air Redox Battery for Advanced Energy Storage
Authors: Zhao Xuan , Gong Yun Hui , Li Xue , Xu Nan Sheng , Huang Kevin
Published: May 2014

This paper reviews the research progress of a new class of solid oxide metal-air redox batteries for advanced energy storage. This new type of battery is comprised of a reversible solid oxide fuel cell and pair of metal/metal-oxide redox couple. This all solid-state battery has a great potential to surpass the conventional metal-air batteries and redox flow batteries in performance and cost. The paper first discusses the working principle and key features of the new battery, followed by the theoretical analysis of various metal-air chemistries. Finally, two examples of solid oxide metal-air chemistries operated at 550°C are given to demonstrate the promising performance of this innovative battery.
High-Pressure Synthesis of Novel Hydrides and Intermetallic Compound in Al-X Systems (X=Sr, V, Hf)
Authors: Kamegawa Atsunori , Abiko Takuya , Okada Masuo
Published: May 2014

Al–based hydrides have been extensively investigated in order to their application for hydrogen storage. To explore new hydrides, the samples in Al–X–H systems (X = Sr, V, Hf) were synthesized at 873–1173 K for 2–8 h under 5 GPa with internal hydrogen source. Unidentified phases in XRD analysis were observed in samples with nominal composition of Al–50mol%SrH2, AlH3–60mol%VH2 and Al–50mol%HfH2. Judging from SEM–EDX analysis, the chemical composition of these phases were Al/Sr=1/1, Al/V=2/3 and Al/Hf=1/2. In Al–Sr system, hydrogen content was determined to be about 2.78mass% by fusion analysis. Corresponding chemical formula of the new hydride was estimated to be AlSrH3 with a perovskite–type crystal structure. Hydrogen desorption of 0.55 mass%H in the Al-60V sample was observed above about 400K by TG–TDS. The new compound, Al2V3H1.8~2.2 had a tetragonal structure. In Al–Hf system, the new compound had almost no hydrogen. Then, the chemical fomula of newly founf compound was estimated to be AlHf2 with a tetragonal structure.
Mechanical Analysis to Improve Reliability and Durability of Solid Oxide Fuel Cells
Authors: Sato Kazuhisa , Hashida Toshiyuki
Published: May 2014

The influence of residual stress, thermal stress and chemically induced expansion stress etc... on the fracture damage of solid oxide fuel cells (SOFCs) were investigated by using nondestructive testing method and numerical stress-strain analyses under operating conditions. In order to estimate stress-deformation behavior of cell/stack of SOFCs, mechanical properties of SOFC elements were evaluated under controlled high temperature and oxygen partial pressure conditions. In addition to deformation and mechanical damage behavior were observed by using acoustic emission method.
Effect of Relative Motion between Weld Tool and Work Piece on Microstructure of Ultrasonically Welded Joint
Authors: Sasaki Tomohiro , Hosokawa Yusuke
Published: May 2014

Ultrasonic welding is conducted using pure aluminum sheets to investigate effect of the transitional welding processes comprised of three transitional stages on the formation of the weld microstructure. In the first stage of ultrasonic welding, the relative motion mainly occurred between the workpieces, and a partially bonded region was observed in the weld interface. In the second stage, the relative motion at the weld interface was suppressed by the formation of the partially bonded region, while relative motion between the weld tool and the workpiece in contact with the weld tool. The relative motion at the weld tool/workpiece caused weld temperature rise with a penetration the weld tool edge. In the third stage, a plastic deformation zone generated by the relative motion at the weld tool/workpiece spread into the lower side of weld part as the welding time increased. It is proposed that the formation of weld microstructure in ultrasonic welding is attributed to the thermo-mechanically effect of the relative motion of the weld tool and workpiece.
High Pressure Materials Physics Research at UNLV
Authors: Cornelius Andrew L. , Abeln Brant , Antonio Daniel , Baker Jason , Kalita Patricia E. , Kumar Ravhi S.
Published: May 2014

High-pressure studies on strongly correlated-electron systems allow the study of the relationship between structural, elastic, electronic, and magnetic properties of d-and f-band systems. The High Pressure Science and Engineering Center (HiPSEC) at UNLV performs interdisciplinary research on a wide variety of materials at high pressures. One such system, YbB2 displays antiferromagnet order at ambient pressure. We present heat capacity measurements at high magnetic fields to 9 T and structural measurement at pressures up to 5 GPa on YbB2.
Fatigue Designing of High Strength Steels Components Considering Aggressive Fuel Environment and Very High Cycle Fatigue Effects
Authors: Issler Stephan , Bacher-Hoechst Manfred , Schmid Steffen
Published: May 2014

Automotive components for injection systems are subjected to load spectra with up to 1E9 load cycles during the expected service life. However, fatigue testing with such a large number of cycles using original components is extremely time-consuming and expensive. A contribution for fatigue reliability assessment is available by the application of specimen testing and the transfer of the results to components including the verification by component spot tests.In this contribution very high cycle fatigue results in laboratory air and in ethanol fuel using notched specimens of high strength stainless steel are discussed. The influence of testing frequency was studied using ultrasonic and conventional test techniques. The validation and transfer of these accelerated testing results to components is one of the main challenges for a reliable fatigue designing.KeywordsVery High Cycle Fatigue (VHCF), automotive components, fuel injection, bio-fuels, corrosion fatigue, testing concepts, fatigue design concepts
Advanced Degradable Alloys for Multi-Stage Fracturing Applications
Authors: Marya Manuel , Reyes Tatiana , Dunne Timothy , Wang Chun Nong
Published: May 2014

New aluminum alloys with unique mechanical and electrochemical properties have been developed in response to a strong demand for new technologies tailored to the expanding hydrocarbon multi-stage fracturing market. The novel alloys disclosed in this paper purposely possess an augmented degradability in water-based oilfield fluids, an unusually high hardness and high compressive strength following proper processing while withstanding thermal aging in wellbore environments. In highlighting major findings from years of research in developing new alloys, this paper overviews major characteristics of these novel alloys from microstructural development, processing, mechanical properties, and electrochemical response in oilfield fluids such as salinated water (brine), acids, and cross-linked fracturing fluids.
Simulation of Radiation-Induced Segregation by the Hybrid Potts-Phase Field Model
Authors: Hernández-Rivera Efraín , Tikare Veena , Wang Lu Min
Published: May 2014

A hybrid model of microstructural evolution of a coupled multi–field system that is subjected to ion irradiation is presented. Materials exposed to low energy ion irradiation experience a wide range of radiation effects, e.g. surface roughening and chemical segregation. The hybrid model combines Monte Carlo methods and a phase field model to simulate the kinetic and radiation-induced processes that lead to radiation induced chemical segregation with associated phase transformations of a binary system by differential diffusivity.
Gas-Liquid In Situ Production of Ceramic Reinforced Aluminum Matrix Nanocomposites
Authors: Ceschini L. , Morri Alessandro , Rotundo F. , Toschi S.
Published: May 2014

The present study aims at evaluating the gas bubbling method, based on the use of dry air as a gaseous phase, for the production of Al based metal matrix nanocomposites through a proper gas-liquid reaction. In particular, Al2O3 reinforcement particles were in-situ synthesized in molten commercially pure Al through a gas bubbling oxidation technique. Dry air was injected in the melt in order to induce a controlled oxidation of the molten matrix. SEM-EDS analysis on the produced samples revealed the presence of alumina particles, ranging from the nanoto the micrometric size, demonstrating the feasibility of the process. A hardness increase on the produced samples confirmed the strengthening effect of the in-situ produced ceramic particles.
Local Strain Distribution in AlN Thick Films Analyzed by X-Ray Microdiffraction
Authors: Khan Dinh Thanh , Takeuchi Shotaro , Nakamura Yoshiaki , Miyake Hideto , Hiramatsu Kazumasa , Imai Yoshihiko , Kimura Shigeru , Sakai Akira
Published: May 2014

We investigated local strain distribution in a cross-sectional area throughout the thickness of a thick aluminum nitride (AlN) film epitaxially grown on a trench-patterned AlN/α-Al2O3 template using X-ray microdiffraction measurements for AlN and Bragg reflections. The results show that the presence of voids caused by the trench pattern strongly influences on the distribution of the strain components in the and directions, which are perpendicular to the trench lines. Discrepancy between strain values obtained from the two Bragg reflections was shown to be the result of twisting of the crystal domains about the axis in the thick AlN film.
Study of Micromechanical Behaviour of Two Phase Polycrystalline Materials Using Diffraction and Self Consistent Model
Authors: Baczmański Andrzej , Gadalińska Elżbieta , Braham Chedly , Wroński Sebastian , le Joncour Lea , Panicaud Benoit , François Manuel , Klosek Vincent
Published: May 2014

Diffraction methods for lattice strain measurement provide useful information concerning the nature of grains behaviour during elastoplastic deformation. The main advantage of the diffraction methods is the possibility of studying mechanical properties of polycrystalline materials separately in each phase and in groups of grains with a specific orientation. In this work we present application of the neutron and X-ray diffraction to study “in situ” deformation of two phase stainless steels during tensile loading. The experimental results are compared with self-consistent model.
Stress Measurements in Polished Al-Mg Alloy and CrN Coating Using Multireflection Grazing Incidence Method
Authors: Marciszko Marianna , Baczmański Andrzej , Wierzbanowski Krzysztof , Chopart Jean Paul , Lodini Alain , Zazi Nacer , Braham Chedly , Seiler Wilfrid
Published: May 2014

The multi-reflection grazing incidence X-ray diffrection was used to determine residual stress gradient in the mechanically polished Al-Mg alloy and CrN coating. Also, the root mean square values of the third order lattice strain was determined using Wiliamson-Hall method. The results obtained for Al-Mg alloy show that the stress field in the surface layer as well as the microstructure (density of dislocation) depend strongly on the sample preparation. A very high residual compressive stress, which does not change significantly with depth, was measured in the CrN coating. Moreover, a large value of the measured third order strains in the coating was found.
New Generation X-Ray Stress Measurement Using Debye Ring Image Data by Two-Dimensional Detection
Authors: Sasaki Toshihiko
Published: May 2014

Measuring theory of two types of X-ray stress analysis method was compared with each other. One is the conventional method, in which zero-or one-dimensional detector is used for obtaining diffracted beam and stress is determined using the standard sin2ψ method. Another is the new type of X-ray stress analysis method, in which two-dimensional detector is used to obtain whole Debye ring and stress is determined using the cosα method. An experiment was conducted to investigate the validity.
Integrated Database Development for Casting Design and its Application to Casting Simulation
Authors: Cho In Sung , Kim Jeong Tae , Choi Jeong Kil
Published: May 2014

Development of integrated database including casting shapes with their casting design, technical knowledge, and thermophysical properties of the casting alloys were introduced in the present study. For the shape database, a number of casting products are scanned by using by using industrial computer tomography and compiled to the shape database. Each shape data in the database has also parametric 3D modeling data, not only the product but also its casting design. If casting engineer want to design new casting, similar casting shape with casting design can be easily retrieved from the shape database, and easily modified and adapted to the new casting. Technical knowledge of the various casting processes and their manufacturing process of the castings were compiled and the search engine for the knowledge was developed. Database of thermophysical properties of the casting alloys were obtained by the experimental study or calculation based on CALPHAD approach, and the properties were used for the in-house computer simulation of casting process. The databases were linked with intelligent casting expert system developed in e-design center, KITECH. It is expected that the databases can help non casting experts to devise the casting and its process. Various examples of the application by using the databases were shown in the present study.
Plating on Developed Al-Mg-Zn Alloy Casting and its Glossiness
Authors: Nagata Norihito , Hino Makoto , Murakami Koji , Kanetsuki Hideki , Kawai Sadao , Kanadani Teruto
Published: May 2014

The purpose of this study is to develop an Al-Mg-Zn series aluminum alloy casting suitable for the plating. We evaluated the influence of the metal structure on the plating process of both AC4CH and a developed aluminum alloy and then examined their suitability to plating. With the AC4CH-T6 casting containing the silicon, it was difficult to obtain a smooth surface by pretreatment process because of the surface irregularity between the hard and chemically stable eutectic silicon and the aluminum matrix. On the other hand, with the developed silicon-free alloy casting, it was possible to produce a smooth surface by pretreatment process, and this glossiness was superior to that of the AC4CH-T6 casting after electroless Ni-P plating. Furthermore, the plating property of the developed casting was also superior to that of the AC4CH-T6 casting, because the zinc deposit on the developed casting from the zincate treatment became uniformly, depending on the uniform displacement reaction.
Statistical and Physical Micro-Feature-Based Segmentation of Cortical Bone Images Using Artificial Intelligence
Authors: Hage Ilige S. , Hamade Ramsey
Published: May 2014

At the micro scale, dense cortical bone is structurally comprised mainly of Osteon units that contain Haversian canals, lacunae, and concentric lamellae solid matrix. Osteons are separated from each other by cement lines. These microfeatures of cortical bone are typically captured in digital histological images. In this work, we aim to automatically segment these features utilizing optimized pulse coupled neural networks (PCNN). These networks are artificially intelligent (AI) tools that can model neural activity and produce a series of binary pulses (images) representing the segmentations of an image. Two segmentation methods were used: one statistical and another based on the physical attributes of the microfeatures. The first, statistical-based segmentation method, cost functions based on entropy (probability of gray values) considerations are calculated. For the physical-based segmentation method, cost functions based on geometrical attributes associated with microfeatures such as relative size, shape (i.e., circular or elliptical) are used as targets for the fitness function of network optimization. Both of these methods were found to result in good quality segregation of the microfeatures of micro-images of bovine cortical bone.
Improving the Working Life of Steel Grinding Balls by Optimizing their Hardness and Tenacity
Authors: Camurri Carlos , Carrasco Claudia , Colàs Rafael
Published: May 2014

The carbon content in steel of the most produced grinding balls, 3 and 5 inch diameter, varies between 0.6% and 1.1% and, due to the presence of other addition elements, after their standard heat treatment, all the ball zones –external and central –reach high hardness values: over 60 RC in the case of the 3 inch diameter balls. The internal zone, hard and with low tenacity, produces a notorious diminution of the working life of the balls with respect to their theoretical potential. In this context, this work has as its objective to improve the quality of the grinding balls of 3 inch diameter, giving them highe r superficial hardness and a central zone with less martensite, and as a consequence, with moderate hardness and adequate tenacity. To perform this, the temperature time transformation (TTT) curves for the steel of the balls was determined by means of calorimetric (DSC) and metallographic analyses. Afterwards, a mathematical model (FDM) for the temperature distribution of the balls during their quenching and equalization treatment was done and experimentally validated. Along with the TTT curves and the math ematical temperature model, new heat treatment conditions were established: a reduced ball quenching time of 55 seconds (instead of the current 80 seconds), with a final central temperature of 500°C (instead of 273°C) and an equalization time of 200 seconds (instead of 40 seconds), and a final ball temperature of 203°C (instead of 139°C). With this new treatment, less martensite was obtained in the central zones of the balls, with an associate hardness on this area of 53-55 RC, while the standard hardness is maintained in their external zones.
Additive Manufacturing Viewed from Material Science: State of the Art & Fundamentals
Authors: Hascoet J.Y. , Karunakaran K.P. , Marya Surendar
Published: May 2014

Additive Manufacturing (AM), also designated as 3D Printing (3DP), is one of the most visionary and friendly approaches for flexible manufacturing with conservation of energy and material resources. It is a factory in a box that can generate multiple objects. It requires little manpower to bring virtual innovations into the real world. AM for metals can be mechanistically associated with welding. The technique employs a variety of energy sources (laser, electron beam, electric Arc, ...), feed stocks (powder, wire and ribbon) and motion kinematics & control (articulated robot and 3-5 axes CNC machine ). From the materials perspectives, akin to fusion welding in many respects, AM involves a multitude of complex and interacting physical phenomena such as heat transfer, fluid flow, discrete and continuum mechanics, sintering, melting, solidification, solid state transformations, grain growth, diffusion, textures etc. The desired process performance can be achieved by controlling the parameters of energy, feed stock and motion. The effect of successive thermal cycles along with the epitaxial relations between substratum and deposits constitute some of the challenging tasks for developing optimized parts. This paper reviews the state of the art and presents some challenges facing metal product development for service applications.
Fatigue, Fatigue Crack Propagation and Mechanical Fracture Behaviour of Laser Beam-Welded AZ31 Magnesium Sheets
Authors: Kashaev Nikolai , Riekehr Stefan , Horstmann Manfred , Ventzke Volker
Published: May 2014

Weight reduction is the main driving force in automotive and aircraft structural design. As a result, magnesium alloys, with their high potential for lightweight construction, have attracted a considerable amount of industrial attention. The determining criterion for the structural applications of magnesium alloys is the availability of efficient joining technologies for the construction of lightweight structures and the availability of reliable data for the assessment of their damage tolerance behaviour. Laser beam welding (LBW), as a high-speed and easily controllable process, allows the welding of complex geometric forms that are optimised in terms of mechanical stiffness, strength, production velocity and visual quality. The work accomplished in this study addresses the challenges of the LBW process for typical joint configurations using the magnesium alloy AZ31HP: butt joints, T joints and overlap joints. LBW processes were developed for use with a 3.3-kW Nd:YAG laser to optimise the mechanical performance of such joints with respect to tensile strength, fatigue, fatigue crack propagation and mechanical fracture behaviour. The relationships between the LBW process and the microstructural and mechanical properties of welds were established. Compared to state-of-the-art aerospace alloys, AZ31HP demonstrates that magnesium alloys have potential for use in structural applications, with AZ31HP being comparable to AA2024T351 and AA6061T6. Welded AZ31HP exhibits better crack resistance than the base material, so fully welded integral structures made from magnesium alloys can be used in lightweight construction.
Plastic Rotational Factor Calculation for Shallow-Notched SE(B) Specimens
Authors: Kayamori Yoichi , Inoue Takehiro , Hagihara Yukito
Published: May 2014

The plastic part of crack tip opening displacement (CTOD) is derived from the plastic hinge model for deep-notched single edge-notch bend (SE(B)) specimens in BS, WES and ISO CTOD testing standards, and a typical plastic rotational factor is given by a constant value of 0.4. This value is appropriate for deep-notched SE(B) specimens, but is not suitable for shallow-notched SE(B) specimens. In this study, a new equation of calculating the plastic rotational factor was obtained by using the Electric Power Research Institute (EPRI) scheme. The equation shows the effect of crack length and strain hardening on the plastic rotational factor, and is useful for evaluating CTOD in shallow-notched SE(B) specimens.
Orientation Correlation during α→β Up-Transformation Induced by Electric Current Pulses in a Cu-Zn Alloy
Authors: Zhao Xiang , Wang Xin Li , Li Dong Xue , Dai Wen Bin
Published: May 2014

In this work, the orientation of the β variants within a single parent α grain on the α→β up-transformation induced by electric current pulses in a Cu-Zn alloy was investigated. Electron backscatter diffraction (EBSD) was used to determine the relationship between the α phase and the β variants. By EBSD analysis, it was found that crystallographic variant selection was observed not only across those prior α/α grain boundaries, but also within the α grain interior. Results revealed that the orientation relationship between the α phase and the β associated with nucleation from α phase was close to the Kurdjumov-Sachs (K-S) orientation relationship, which better described the orientation relationship for α nucleation within β grains.
Mechanical Properties of Ti-Fe-Sn Biomedical Alloys with or without Aging Treatment
Authors: Hosoda Hideki , Kasuya Kenta , Tahara Masaki , Inamura Tomonari , Miyazaki Shuichi
Published: May 2014

In order to develop new β (bcc) Ti alloys, the Ti-Fe-Sn system was focused and phase constitution, microstructure, mechanical properties of Ti-5mol%Fe-6mol%Sn and Ti-6mol%Fe-3mol%Sn were clarified in addition to aging effect. It was estimated by differential scanning calorimetry (DSC) that α phase is formed at temperature from 773-779K and that β transus temperature is 1019K in both the alloys. X-ray diffraction analysis revealed that, in both alloys, β single phase is formed after the solution treatment (ST) at 1273K followed by water quenching, while α phase is formed after the aging at 773K and 873K for 3.6ks. The formation of α phase is also confirmed by optical microscopy. The volume fraction of α phase reaches to 90% in Ti-5Fe-6Sn and 80% in Ti-6Fe-3Sn after the aging at 873K for 3.6ks. The 0.2% proof stress was increased by aging at 873K from 550MPa to 650MPa in Ti-5Fe-6Sn and 500MPa to 690MPa in Ti-6Fe-3Sn. Besides, apparent Young’s modulus measured by dynamic mechanical analysis was raised by the aging treatment. These changes in the mechanical properties were discussed in connection with α phase precipitation.
Influence of Co on Strength of Cu-Ni-Co-Si Alloy
Authors: Ozawa Atsushi , Watanabe Chihiro , Monzen Ryoichi
Published: May 2014

The effects of Co on the strength of Cu-Ni-Co-Si alloys have been investigated using Cu-2.0wt%Ni-0.5wt%Si (0%Co), Cu-1.4wt%Ni-0.6wt%Co-0.5wt%Si (0.6%Co) and Cu-1.0wt% Ni-1.0wt%Co-0.5wt%Si (1.0%Co) alloys produced by combining cold rolling to a 25% reduction with aging. Aging the 0.6%Co and 1.0%Co alloys at 525 and 425°C produces orthorhombic (Ni, Co)2Si precipitates that have the same crystal system as Ni2Si precipitates formed in the 0%Co alloy. The larger the amount of Co in the three alloys is, the higher the strength and electrical conductivity of the alloys initially aged at 525°C, rolled to a 25% reduction and re-aged at 425°C become. The increase in strength with increasing Co content is caused by both of the decrease in inter-precipitate spacing and increase in dislocation density. The increase in strength by re-aging at 425°C becomes more pronounced as the Co content increases. This arises because the larger the amount of Co is, the larger the difference between the equilibrium solubilities at 525 and 425°C becomes, the more the volume fraction of precipitates is increased by re-aging at 425°C.
Near-Net Shaping of Silicon for Optical Lens by One-Shot Pressing at Temperature just below Silicon Melting Point and Improvement of Infrared Transmittance by Primary Recrystallization
Authors: Morishita Kohei , Nakajima Kazuo , Fujii Takashi , Shiinoki Masakazu
Published: May 2014

Silicon is brittle and easily cracks even under a small load. The difficulty in shaping silicon has prevented breakthroughs in the mass production of silicon lenses for terahertz and infrared technology. We developed a novel method of deforming bulk single-crystal silicon into the required shape by one-shot pressing at a temperature just below the melting point of silicon, despite its brittleness and covalent nature, and realized the near-net shaping of the material into the plano-convex shape with the curvature radius R=7.5 mm for a infrared transmission lens. The crystallographic quality of the obtained lens could be improved by primary recrystallization. The simple method of 'pressing' will enable the mass production of not only silicon lenses but also lenses with a complex shape, such as aspherical lenses, and lens arrays by using dies with desired shape.
Hardening of Al-Mg-Si Alloys and Effective Particle Size in Microstructural Models
Authors: Gulbrandsen-Dahl Sverre , Marthinsen Knut
Published: May 2014

It is well established that the precipitate volume fraction and size are the dominating parameters determining the hardening in Al-Mg-Si alloys. Several empirical models of the relationship between precipitate morphology and hardening have been published, but the coherency strain field surrounding the particles has so far not been taken into account. The authors have earlier published data with characterisation of microstructure of aged Al-Mg-Si alloys, including estimation of the coherency strain field surrounding these (semi-) coherent precipitates. In this paper the effect of including the coherency strain field as part of the effective hardening diameter of the precipitates in hardening models is evaluated. The correlation between the tensile test results and mechanical properties calculated with an appropriate microstructural model increased from 0.78 to 0.87, by implementation of coherency strain field as part of the effective particle radius in the model.
Microstructures and Mechanical Properties of Two-Phase FeNiMnAl Alloys
Authors: Baker Ian , Wu Xiao Lan , Meng Fan Ling , Munroe Paul R.
Published: May 2014

This paper presents an overview of the microstructures found in a range of two-phase FeNiMnAl alloys ranging from near-equiatomic very high-strength nanostructured alloys, such Fe30Ni20Mn25Al25, to more ductile f.c.c./B2 alloys, such as Fe30Ni20Mn35Al15. The effect of annealing at 823 K on the room temperature hardness is presented together with the temperature dependence of the yield strength.
Ultrafine Grain Evolution in a Cu-Cr-Zr Alloy during Warm Multidirectional Forging
Authors: Shakhova Iaroslava , Belyakov Andrey , Zhilyaev Alexander P. , Kaibyshev Rustam
Published: May 2014

The microstructure evolution and the deformation behavior of a Cu-0.3%Cr-0.5%Zr alloy subjected to multidirectional forging at a temperature of 673 K under a strain rate of about 10-3 s-1 were studied. Following a rapid increase in the flow stress during straining to about 1, the strain hardening gradually decreases, leading to a steady-state flow behavior at total strain above 2. The multidirectional forging led to the development of ultrafine grained microstructures with mean grain sizes of 0.9 μm and 0.64 μm in the solution treated and aged samples, respectively. The presence of second phase precipitates promoted the grain refinement. After processing to a total strain of 4, the fractions of ultrafine grains (D < 2 μm) comprised 0.36 and 0.59 in the solution treated and aged samples, respectively.
Microstructure and Aging Behavior of Cu-Be Alloy Processed by High-Pressure Torsion
Authors: Watanabe Chihiro , Monzen Ryoichi , Ii Seiichiro , Tsuchiya Koichi
Published: May 2014

The microstructure and aging behavior of Cu-1.8wt%Be-0.2wt%Co alloy specimens processed by high-pressure torsion (HPT) at room temperature (RT) and 150°C after solution treatment have been studied. Application of HPT processing at RT and 150°C under an applied pressure of 5 GPa for 10 revolutions at 1 rpm to alloy specimens (RT-and 150°C-specimen) produces an ultra-fine grained structure with a grain size of 70 nm. The hardnesses of the RT-and 150°C-specimens increase with equivalent strain up to 7 and then saturate at constant values of 400 and 430 Hv, respectively. Annealing the RT-specimen at 150°C for 10 min increases the hardness from 400 to 430 Hv. Transmission electron microscopy observations of the 150°C-specimen and the RT-specimen annealed at 150°C reveal that there are no intragranular and intergranular precipitates. It is suggested that the higher hardness of the 150°C-specimen than the RT-specimen is ascribed to the segregation of Be atoms on dislocations during HPT processing at 150°C. The RT-and 150°C-specimens harden rapidly and exhibit maximum values of hardness at 3 min during aging at 320°C. The increase in the hardness is attributed to the precipitation of finely dispersed G.P. zones.
The Effect of Shielded Metal Arc and Gas Tungsten Arc Welding Methods on 308L Stainless Steel Weldments
Authors: Lin Shao Pin , Yu Ge Ping , Huang J.Y. , Chen H.J. , Kuo R.C. , Huang E Wen , Huang Jia Hong
Published: May 2014

Shielded metal arc (SMA) and gas tungsten arc (GTA) weldments were investigated to study the welding effects on the mechanical behavior of 308L austenitic stainless steel weldments, respectively. Both SMA and GTA weldments showed dendritic microstructure. The observed austenitic stainless steel welds solidified to give primary ferrite and secondary austenite as the ferritic-austenitic solidification mode (FA-mode) solidification. However, the lower heat input with larger Cr-versus-Ni ratio in SMA weld process led to lathy ferrite morphology and more residual ferrite in the SMA welds, while vermicular ferrite morphology was shown in GTA weldments. The yield strength of the welds significantly increased with decreasing elongation, which was mainly due to the dual phase strengthening effect after rapid solidification during welding
Grain Refinement of Al Cast by Novel Al-Al2.5Cu0.5Ti Refiner Fabricated by Cold Pressing
Authors: Yamanaka Kunika , Sato Hisashi , Watanabe Yoshimi
Published: May 2014

It is reported that alloying with Cu causes the transformation from the D022 type structure of Al3Ti into L12 cubic structure. Since the lattice constant of Al2.5Cu0.5Ti with L12 structure is a = 0.3927 nm, smaller disregistry value between Al and Al2.5Cu0.5Ti can be achieved. In this study, novel refiner for Al cast containing Al2.5Cu0.5Ti intermetallic compound particles with L12 structure is fabricated by cold pressing. It is found that the grains of Al cast are partially refined by using the novel refiner, although microstructure of Al grain is not homogeneous. In this way, the Al2.5Cu0.5Ti intermetallic compound particles with L12 structure can become favorable heterogeneous nucleation sites for Al cast.
Hybrid Laser-Arc Welding of AA6061-T6 Butt Joints
Authors: Wanjara Priti , Cao Xin Jin
Published: May 2014

Hybrid laser-arc welding (HLAW) of butt joints in 3.18 mm thick aluminum alloy (AA) 6061-T6 sheets was investigated in the present study. Under optimized process conditions, high integrity welds with approximately 2% shrinkage and gas porosity were obtained. The weld bead geometry was determined to conform to the crown and root reinforcement specifications for welded aluminum construction - CSA W 59.2 M1191. Softening in the heat-affected zone (HAZ) and fusion zone (FZ) of the welds was observed, the former due to grain coarsening and the latter due to the dissolution of the hardening precipitates as well as the dilution from the application of the ER 5356 filler wire. Under optimized process conditions, the gap tolerance was determined to be 0.5 mm, beyond which the performance of the joints during bend testing was compromised.
Deformation Behavior of Fe-Al-Co Single Crystals Containing CoAl Precipitates
Authors: Yasuda Hiroyuki Y. , Soma Kentaro , Odawara Yoshiaki
Published: May 2014

The effect of the CoAl precipitates on the deformation behavior of Fe-15.0Al-15.0Co (at.%) single crystals was examined. The spherical CoAl phase with the B2 structure was precipitated in the single crystals and was stable below 974 K. The bcc matrix and CoAl phase satisfied the cube-on-cube orientation relationship with a misfit strain of 0.25%. The single crystals showed a high yield stress up to 923 K while the stress dropped at 1023 K due to the dissolution of the CoAl phase into the matrix. Moreover, the activated sip system of the crystals containing the CoAl precipitates depended strongly on loading axis. At <149> orientation, {101} <111> slip favorable for the bcc matrix and the CoAl precipitates were sheared by a pair of 1/2<111> dislocations without forming Orowan loops. The CoAl single phase was known to hardly deform by <111> slip which resulted in high strength at <149> orientation. In contrast, {010} <001> or {hk0} <001> slip favorable for the CoAl precipitates was activated at <011> orientation, although the volume fraction of the CoAl phase was very small. <001> slip was generally impossible to take place in the bcc matrix, leading to the extreme hardening. Therefore, the difference in primary slip system between the bcc matrix and CoAl precipitates was responsible for the significant precipitation hardening.
Degradation of Magnesium Alloys in Artificial Urine Solution for Urological Device Applications
Authors: Lock Jaclyn Y. , Tu James , Liu Hui Nan
Published: May 2014

Magnesium-based alloys are promising for various biomedical applications due to their advantageous mechanical and biological properties. In this study, we investigated the potential use of magnesium-based alloys for urological device applications, e.g. a biodegradable and antibacterial ureteral stent. Previous studies showed that magnesium-based samples significantly inhibited bacterial growth and colony formation in artificial urine (AU) solution as compared with the polyurethane-based stent. This current study focuses on long-term magnesium-based sample degradation in AU solution and deionized water. We studied the effects of alloy composition (magnesium alloyed with yttrium or aluminum and zinc) and surface condition (oxide versus metallic surface) on the rate of degradation. Sample degradation was measured by the change in sample mass, pH of immersion solution, and magnesium ion concentration in the solution. Results showed that both alloy composition and surface condition affected the rate of degradation in the AU solution. For instance, magnesium-yttrium alloy degraded the fastest and the presence of the oxide layer increased its degradation rate in the AU solution. The overall degradation rate in the AU solution was in this order (fastest to slowest degrading): MgY_O > MgY > Mg_O > AZ31. Further investigation is necessary to determine the efficacy and safety of magnesium-based biodegradable stents for urological applications.
Low Temperature Warm Forming of Magnesium ZEK 100 Sheets for Automotive Applications
Authors: Niu Xiao Ping , Skszek Tim , Fabischek Mark , Zak Alex
Published: May 2014

Cosma R&D investigated a low temperature warm forming process by which a magnesium ZEK 100 door inner part with a single-stage draw depth of 144 mm was successfully formed. The warm forming process is comprised of three steps: 1) heating pre-lubricated blanks in an oven at temperatures ranging from 215°C to 260 °C, 2) robotic transfer of the heated blank to a mechanical stamping press, 3) forming of the panel in room temperature stamping die at speed of about 160 mm/s. The effect of process parameters on the formability of the part, as well as, the post-forming properties including the mechanical properties, microstructure evolution and deformation thinning are also presented. The result indicates that Magnesium ZEK 100 exhibits superior low temperature warm formability over Magnesium AZ31B, and the developed warm forming process is promising and potential for volume production of magnesium automotive parts.
A New Model for Discontinuous and Continuous Precipitation in AZ91 Magnesium Alloy
Authors: Robson Joseph D.
Published: May 2014

The Mg-Al-Zn alloy AZ91 is age hardenable, forming precipitates of –Mg17Al12 after suitable heat treatment. In this alloy both continuous and discontinuous precipitation canoccur. These modes are in competition and lead to very different microstructures. In this paper,a new model is developed to predict this competitive precipitation. The model is validated usingliterature data and then used to study the competition between precipitation modes and predictthe effect of cooling rate from solution treatment on the microstructure expected in AZ91.