bluuebunny/crossref_metadata_2025 huggingface dataset:
Precipitation and Precipitation Hardening Behavior of V and/or Cu Bearing Middle Carbon Steels
Authors: Senuma Takehide , Sakamoto Masanori , Takemoto Yoshito
Published: January 2010

In this study, the precipitation and precipitation hardening behavior of a 0.3%V and 2%Cu bearing middle carbon steel has been investigated in comparison with that of a 0.3%V bearing steel and a 2%Cu bearing steel. The precipitation treatment was carried out isothermally at 600°C.The amount of the precipitation hardening of the 0.3%V and 2%Cu bearing steel is nearly equal to the sum of the precipitation hardening of the 0.3%V bearing steel and the 2%Cu bearing steel
In the 0.3%V bearing steel, precipitates were observed in rows, which indicates the occurrence of the interphase precipitation while precipitates observed in the 2%Cu bearing steel were randomly dispersed. In the V and Cu bearing steel, randomly dispersed precipitates were not observed where there were aligned precipitates. In the paper, the different precipitation behavior of the three steels is discussed.
Direct Observation of the Change in Microstructure with Deformation in Ferrous Lath Martensite by Using Micro-Sized Specimen
Authors: Shibata Akinobu , Ogawa Yuichiro , Sone Masato , Higo Yakichi
Published: January 2010

In the present study, the micro-sized cantilever-beam type specimens containing only one block of lath martensite were fabricated, and change in deformation microstructure inside a block with strain was observed directly by scanning electron microscopy and transmission electron microscopy. A number of slip bands appeared in the fixed end of the specimen by deformation. The propagations of slip bands, however, terminate due to the gradient of strain inside the specimen. The direction of slip bands changed during the propagation by the low angle boundaries inside the block. The shear localized region becomes narrow with an increase in strain. Furthermore, the width of laths increases greatly at the large strain region. The increase in width of laths is attributed to the disappearance of some initial lath boundaries by deformation.
The Influence of Deformation on Microstructure Evolution of Low Alloy TRIP Steel
Authors: Suarez Lucia , Benito Josep Antonio , Rodriguez-Calvillo Pablo , Casellas Daniel , Houbaert Yvan , Petrov Roumen H. , Prado Jose Manuel
Published: January 2010

Low alloy transformation-induced plasticity aided (TRIP) steels have attracted much interest over the last years. TRIP steels were initially developed for automotive applications as they offer an excellent combination of strength and ductility at reasonable costs. These excellent mechanical properties mainly arise from a complex multiphase microstructure of a ferrite matrix and a dispersion of multiphase grains of bainite, martensite and metastable retained austenite. The relevant influence of microstructure on physical and mechanical properties makes metallographic study essential for an appropriate understanding and improvement of the mechanical behavior.
An accurate microstructural characterization and quantification of the amount of the different constituents is indispensable to know how the stresses and strains are distributed within the different microstructural constituents. Among the different characterization methods commonly used electron backscatter diffraction (EBSD) appears to be the unique technique able to observe retained austenite grains often no larger than 1 μm. The present work shows the evolution of retained austenite while straining. Microstructural and textural evolution after different strains was examined by optical microscopy OM, EBSD and XRD techniques on TRIP800 steel.
EBSD technique appears as a powerful tool for characterizing the complex multiphase steel microstructure and provides an accurate evaluation of the local crystallographic texture. It allows to measure orientation gradients within individual grains of each different phase. The distinction between some phases is observed.
High Temperature Deformation Mechanisms and Processing Map for Hot Working of Cast-Homogenized Mg-3Sn-2Ca Alloy
Authors: Rao Kamineni Pitcheswara , Prasad Yellapregada Venkata Rama Krishna , Hort Norbert , Kainer Karl Ulrich
Published: January 2010

The hot working behavior of Mg-3Sn-2Ca alloy has been investigated in the temperature range 300–500 oC and strain rate range 0.0003–10 s-1, with a view to evaluate the mechanisms and optimum parameters of hot working. For this purpose, a processing map has been developed on the basis of the flow stress data obtained from compression tests. The stress-strain curves exhibited steady state behavior at strain rates lower than 0.01 s-1 and at temperatures higher than 350 oC and flow softening occurred at higher strain rates. The processing map exhibited two dynamic recrystallization domains in the temperature and strain rate ranges: (1) 300–420 oC and 0.0003–0.003 s-1, and (2) 420–500 oC and 0.003–1.0 s-1, the latter one being useful for commercial hot working. Kinetic analysis yielded apparent activation energy values of 161 and 175 kJ/mole in domains (1) and (2) respectively. These values are higher than that for self-diffusion in magnesium suggesting that the large volume fraction of intermetallic particles CaMgSn present in the matrix generates considerable back stress. The processing map reveals a wide regime of flow instability which gets reduced with increase in temperature or decrease in strain rate.
Cutting Performance of Diamond-Like Carbon Coated Tool in Cutting of Aluminum Alloys
Authors: Wada Tadahiro
Published: January 2010

In cutting aluminum alloy 6061, continuous chips have a negative influence on the machining operation. Usually, Pb is added in order to break continuous chips. However, from the standpoint of environmental protection, it is necessary to improve chip breakability without adding Pb. One effective measure is improving chip breakability by adding Si in aluminum alloy 6061. However, the influence of Si content on tool wear has not been fully examined. In this study, in order to clarify the influence of a diamond-like carbon (DLC) coating layer on cutting performance, aluminum alloys having different Si contents were turned. The substrate of the tool material was high speed steel (1.4%C). The chip configuration, cutting force and tool wear were experimentally investigated. The following results were obtained: (1) The DLC coating layer was effective for decreasing the cutting force. (2) In cutting Al-2mass%Si alloy, the wear progress of the DLC-coated tool was slower than that of the un-coated tool. The length of a chip with the DLC-coated tool was shorter than that with the un-coated tool.
Thermomechanical Joining of Aluminium Alloys: Effects of the Shear on the Quality of the Joining
Authors: Siret O. , Desrayaud Christophe , Tourabi M.A.
Published: January 2010

Thanks to their oxide layer, aluminium alloys are remarkable for their ability to resist corrosion. However, in welding, this protective layer acts as a barrier which must be broken in order to succeed in the thermomechanical joining of aluminium.
The chosen alloy (6082-T6 or AlSi1MgMn) has been subjected to various deformation path. The first of them consists in the channel-die (plane strain) compression of two cuboids, one above the other. Considering the configuration of the test, the surface size between the two samples rises, so that the fragmentation of the oxide layer creates welding bonds. However, the friction effects in the channel lead to a heterogeneous deformation, so that the contact surface undergoes different behaviors: a microscopic study then shows that the welds appear in areas with significant shear.
Channel-die and uniaxial compressions of beveled samples confirm that more significantly than the global deformation, the shear strain is the most active phenomenon for achieving an effective thermomechanical joining.
Another approach is the cumulative deformation as a result of a cyclic load: a tube is cut through its section and undergoes both a compression and cyclic torsion load. The contact surface between the two semi-tubes is under a shear behavior and the combination between plastic deformation and local heating leads to a fragmentation of the oxide layer: all this factors allow the thermomechanical joining of aluminium alloys.
Fatigue Behaviour of Friction Stir Processed Cast Aluminium and Magnesium Alloys
Authors: Uematsu Yoshihiko , Tokaji Keiro
Published: January 2010

Friction stir processing (FSP) was applied to a cast aluminium alloy, A356-T6, and a cast magnesium alloy, AZ91-T5, and fully reversed axial fatigue tests have been performed using FSPed specimens. It was indicated that FCP exerted different influence on fatigue behaviour depending on alloy system. In A356-T6, the fatigue strengths of the FSPed specimens were lower than those of the as-cast ones in the finite life region, but the fatigue limit was significantly increased by FSP. The enhanced crack initiation resistance due to the elimination of casting defects by FCP resulted in the improvement of fatigue limit of the FSPed specimens, while the matrix softening due to the dissolution of precipitates by the heat input during FSP caused faster crack growth rates in the FSPed specimen, leading to the inferior fatigue strength of the FSPed specimens to the as-cast one in the finite life region. In AZ91-T5, both the fatigue strengths in the finite life region and fatigue limit were improved by FSP, because the hardness was increased and both the crack initiation and crack growth resistances were enhanced.
On the Microstructures of Spray-Deposited and Homogenized Al-Zn-Mg-Cu Alloys
Authors: Xiong Bai Qing , Wang Feng , Zhang Yong An , Zhu Bao Hong , Liu Hong Wei , Li Zhi Hui , Zuo Yu Ting , Zhang Ji Shan , Frichting Udo , Bauckhage Klaus
Published: January 2010

In this study, a high strength Al-Zn-Mg-Cu alloy was prepared by the spray deposition technique. The microstructures of spray-deposited and homogenized Al-Zn-Mg-Cu alloys were studied using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results indicate that the microstructure of the spray-deposited alloy mainly is composed of the Al matrix and the Mg(ZnCu)2 compounds. The spray-deposited process has an obvious modification in size, morphology and distribution of the secondary phases in the microstructure as well as reduce of segregation. After homogenization, the coarsening of the grains in the microstructure is not obvious, a phase transformation of primary Mg(ZnCu)2 particles to Al2CuMg phase was found.
A Weldability Study of Nickel-Iron-Cobalt Hydrogen Resistant Alloys Using Weld Simulation in Parallel with Variable Restraint Testing
Authors: Walsh D.W. , Bright Mark L. , Jackson Trevor L. , Gibbs D.B.
Published: January 2010

Incoloy 903 overlays have been used to provide hydrogen environment embrittlement (HEE) resistance to welds in nickel alloy 718 structures. This is problematic because application of the required overlays has a history of high rejection and rework due to interpass microfissuring. Kovar has been identified as a potential hydrogen resistant replacement for Incoloy 903. A weldability study was initiated to compare the hot crack (microfissure) resistance of the two alloys to determine if substitution of Kovar for Incoloy 903 has the potential to improve the fabricability of HEE overlays. Varestraint testing indicates that Kovar has much higher crack initiation strains for both HAZ and weld metal cracking. Crack initiation strains were approximately 2% for Kovar while Incoloy 903 crack initiation strains were only 0.25% . Maximum crack lengths (MCL) observed on Kovar Varestraint tests were 0.12mm and 0.58mm for base and weld metal respectively, while 903 MCLs were 0.56mm and 2.3mm. Gleeble hot ductility testing indicates that Kovar has a nil ductility range of 7 degrees C while Incoloy 903 has a range of approximately 45 degrees C. The larger range observed for 903 is an indication of its greater crack susceptibility. Fabricability was correlated to material microstructure using optical microscopy, scanning electron microscopy and microprobe analysis.
In Situ Observation of Phase Transformations during Welding of Low Transformation Temperature Filler Material
Authors: Kromm Arne , Kannengiesser Thomas , Gibmeier Jens
Published: January 2010

Tensile residual stresses introduced by conventional welding processes diminish the crack resistance and the fatigue lifetime of welded components. In order to generate beneficial compressive residual stresses at the surface of a welded component, various post-weld treatment procedures are available, like shot peening, hammering, etc. These post-weld treatments are, however time and cost extensive. An attractive alternative is to generate compressive stresses over the complete weld joint in the course of the welding procedure by means of so-called Low Transformation Temperature (LTT) filler materials. The volume change induced by the transformation affects the residual stresses in the weld and its vicinity. LTT fillers exhibit a relatively low transformation temperature and a positive volume change, resulting in compressive residual stresses in the weld area.
In-situ measurements of diffraction profiles during real welding experiments using Gas Tungsten Arc (GTA)-welding process were realized successfully for the first time. Transformation temperatures during heating and subsequent cooling of LTT welding material could be assessed by means of energy dispersive diffraction using high energy synchrotron radiation. The results show that the temperature of martensite start (Ms) is strongly dependent on the content of alloying elements. In addition the results indicate that different phase transformation temperatures are present depending on the welding depth. Additional determination of residual stresses allowed it to pull together time and temperature resolved phase transformations and the resulting phase specific residual stresses. It was shown, that for the evaluation of the residual stress state of LTT welds the coexisting martensitic and austenitic phases have to be taken into account when describing the global stress condition of the respective material in detail.
The Mechanism of Failure of the Axisymmetrical Welded Joint under Thermomechanical Loading
Authors: Lacki Piotr , Wojsyk Kwiryn , Służalec Andrzej
Published: January 2010

The purpose of the paper is to present the mechanism of deformation and failure of welded joints during the process of retrofit. The considered joints are made of conventional steels used in the power industry, as well as new-generation steels. The problems of failure and the design of such joints are considered in the paper. The model of welded joint was built with properties of low alloyed chrome-molybdenum steel and a new-generation steel of P/T91 type. All metallurgical zones, i.e. the weld and the heat-affected zone were considered, modelled and discussed. A simulation of thermomechanical loading was conducted under various loading conditions to explain the causes of the failure of energy structures, which appears more frequently during their loadings or steam dropping (i.e. in conditions of changes of thermal loadings) than during their stable work. The results of calculations were confirmed by experimental metallurgical studies. It is observed that the brittle and soft zones of coarse-grained ferrite with minimal impact strength, resulting from internal and external operation parameters, appear in regions where oscillation of the highest von Mises and normal stresses takes place. The relevant literature does not describe the analysis of the phenomenon of acceleration of the failure of the welded structure leading to its failure, while taking into account the complex thermomechanical conditions of their operation. This mechanism is based on the accumulation of structural weakening of the weld as the result of the diffusion process within the axially symmetrical joint, the growth of the brittle zone and their additional degradation, and the influence of the oscillation of maximal normal and von Mises stresses.
It was noted that in the process of thermomechanical loading, the state of failure initiation in circumferential and longitudinal directions appeared in the weld. A few illustrations presenting the mechanism of the deformation and failure of the welded joint are presented. The effects of the distortions of the weld are also discussed in the paper.
Microstructure Evolution of Sn-2.5Ag-2.0Ni Solder Joint with Various Ni Platings on SiCp/Al Composites
Authors: Wu Mao , He Xin Bo , Ren Shu Bin , Qin Ming Li , Qu Xuan Hui
Published: January 2010

A novel Sn-2.5Ag-2.0Ni alloy has been developed for soldering of SiCp/Al composites substrate with various types of Ni coatings. An investigation about electroplated Ni layer, electroless Ni-5 wt.% P, Ni-10wt.% P and Ni-B layers has been carried out. It is found that the solder joints possess a single intermetallic compound (IMC) Ni3Sn4, which coarsens with an increase in aging time. The formation of Ni2SnP has been observed to significantly affect the reliability of the solder joints. But the formation of Ni2SnP can be suppressed by lowering the P contents in as-deposited Ni coatings. It has been also found that the thermal stresses generated in solder joint increases with the decrease of P contents in Ni-P layer. Furthermore, the concentration of thermal stresses in the electroplated Ni solder joint is found to be higher than that in other three electroless Ni layers. Out of four as-deposited Ni coatings, the Ni-B layer exhibits good wettability with solder and low IMC growth rate during aging. Also, the shear strength of solder joint decreases with an increase in aging time and Ni-B solder joint demonstrates the highest shear strength after long term aging.
Effect of Strain Heterogeneity on the Recrystallization Behavior of an Oxide Dispersion Strengthened Ferritic Alloy
Authors: Chen Chun Liang , Tatlock G.J. , Jones Andy R.
Published: January 2010

Oxide Dispersion Strengthened (ODS) Fe-based alloys often contain 0.5wt% of fine, uniformly dispersed, yttrium oxide particles in a Fe-Cr-Al matrix. They are ideal candidates for high temperature applications such as high temperature heat exchangers or nuclear power plants due to their good combination of creep and oxidation resistance. Numerous studies of annealing phenomena have shown that nucleation and growth of recrystallized grains, as well as the recrystallization texture, strongly depend on the deformed state of a previously cold worked alloy. In the present work, we examined the effect of strain heterogeneity on the development of recrystallized grain structures using bend samples. A bend test introduces a stress gradient and both compressive and tensile deformation. After a further heat treatment at 1380°C for 1 hour in air, the recrystallization behavior was characterized on both the tension and compression sides of the samples at varied levels of strain. Electron backscattering diffraction (EBSD) was used to analyze recrystallization behavior and texture. The results demonstrated that: recrystallized grains only formed in areas of sample subject to plastic compression; maximum grain size increased with increasing severity of bending deformation; there was heterogeneity in the recrystallized grain size, which varied with distance from the bending neutral axis. This indicates that the strain heterogeneity conducive to recrystallization was introduced by the non-uniform plastic strains in the compression region. However, the regions of tensile bending in all samples remained unrecrystallized and strong shear banding was evident.
A Proposal for Two Characteristic Ratios of ASTM-CTOD to BS-CTOD
Authors: Kayamori Yoichi , Inoue Takehiro , Tagawa T.
Published: January 2010

There have been two different CTOD calculations, geometric CTOD calculation in BS7448 and J-based conversion in ASTM E1290 since the ASTM International revised E1290 in 2002, and it is useful to transform one CTOD into the other CTOD. In this study, analytical and experimental investigations into the ratio of ASTM E1290-CTOD to BS7448-CTOD were carried out, and two ratios of ASTM-CTOD to BS-CTOD, R1 and R2, were characterised in terms of cleavage cracking. These two characteristic CTOD ratios are helpful in simply transforming one critical CTOD to the other.
Deformation in Ti-Nb-Ta-Zr-O Alloy at Near Ideal Strength
Authors: Kuramoto Shigeru , Furuta Tadahiko , Nagasako Naoyuki , Hara Masashi
Published: January 2010

Recent experimental results on phase stability and deformation behavior in a multifunctional Ti-36Nb-2Ta-3Zr-0.3O alloy, Gum Metal, are summarized and its deformation mechanisms are discussed. The crystal structure of the alloy is essentially unstable to tensile loading in <110> direction, but the microstructure of the cold worked state stabilizes the crystal structure. Work hardening in Gum Metal was far smaller than the other materials even when huge amount of strain is accumulated by severe plastic deformation. By comparing actual applied stress during plastic deformation with ideal shear strength, the alloy is likely to deform at near ideal strength with stress concentrations along with the highly inhomogeneous deformation behavior.
On the Effects Associated with Control Parameters Delay during Biaxial Cyclic Loading of Engineering Materials
Authors: Kowalewski Zbigniew L. , Szymczak Tadeusz
Published: January 2010

The paper presents experimental results of investigations carried out on the P91 steel and 2024 aluminium alloy under complex stress states due to various combinations of an axial force and twisting moment. An influence of out-of-phase sinusoidal and trapezoidal strain signals on the mechanical behaviour of tested materials was considered. The experiments enabled identification of the second order effects connected with the non-proportional cyclic loadings such as the phase shift between stress and strain signals during the deformation along the circular strain path, and a significant stress drop of the one of loading components applied in the case of deformation enforced by the trapezoidal signals. The experimental programme also contained the tests of monotonic tensile deformation realized simultaneously with delayed torsional cycles. They enabled to observe a drastic variations of the proportional limit and yield point of the materials in the tensile direction. This fact manifests an important material feature which can be applied to the optimal designing of some metal forming processes like an extrusion or forging for example.
Characterization of Lanthanoid and Aluminum Based Oxide Film for Wide Bandgap Semiconductors
Authors: Aoki H. , Komatsu N. , Honjo M. , Masumoto K. , Kimura C. , Sugino T.
Published: January 2010

A gate insulator film with a wide bandgap and a high dielectric constants required to achieve
high power field effect transistor (FET) using wide bandgap semiconductors such as SiC and diamond.
We can achieve to suppress the gate leakage current and the charge shifts by using the AlSiO film. We
found that the leakage current of Nitrogen-doped AlSiO film can be suppressed in high temperature
region compared with AlSiO film. In addition, we attempted to study Yttrium aluminate (YAlO) and
Lanthanum aluminate (LaAlO) as a gate insulator film. Since the Y (+3) and La(+3) have the same
valence as Al (+3), it is expected that there is an advantage that Y, La doping generates less dangling
bonds in the Al2O3 film. We can achieve to form aluminum based oxide film with higher dielectric
constant by doping Lanthanoid atoms such as Y and La. The optimized YAlO and LaAlO films were
applied to SiC-MIS structure. The Lanthanoid and Aluminum based oxide films can readily be
applicable to wide bandgap semiconductor devices.
Microstructural and Mechanical Studies in Al-Mg Based Alloys Obtained by Conventional and P/M Processes after Special Thermomechanical Treatments
Authors: Monteiro Waldemar Alfredo , Buso S.J. , Ferrari R.B.
Published: January 2010

Al-Mg based alloys have special attention due to the lightness of the material and certain mechanical properties and recyclability. Normally classified as non-heat-treatable these alloys obtain higher strength either by strain-hardening or by solid solution. The P/M process in the Al-Mg alloys in study leading to fine grain structure after the thermal treatment. The direct observation were made in a JEOL 200C and 2010 TEM combined with mechanical characterization utilizing Vickers microhardness measurements. The samples preparation followed the usual route of metallographic specimen preparation. The understanding of the observed phenomena depends of the fact that materials produced by powder metallurgy present complex interface reactions in a great amount of nucleation sites and a subtle change in the structure of the material causes an important variation in your properties. Alloys in study presented interesting values of properties, with evident technological potential.
Heat Treatment Variability Effects on the Mechanical Properties of Beta Solution Treated Ti-6Al-4V
Authors: Calcaterra J.R.
Published: January 2010

Beta solution heat treatment is used to increase the fatigue crack growth resistance of Ti-6AL-4V. Unfortunately, the beta solution heat treatment is very sensitive to maximum temperature, time at temperature and cooling rate. In order to determine the effect of these parameters on mechanical properties, several different titanium billets and forgings were heat treated at various times and temperatures. The forgings had differing amounts of work, reflecting the potential for thermomechanical processing differences seen in a die forged component. Fracture toughness and tensile tests were conducted on the billets and forgings. In addition, sections of each work piece were excised and examined microscopically. The results from the study indicate there is a significant effect of heat treatment on thicker section components. In these cases, grains near the surface may grow large, while being barely transformed near the center. The change in microstructure has an effect on mechanical properties. Material with the larger grains tends to have worse ductility, while the fracture toughness properties of the material tend to decrease with grain size.
Friction Stir Welding of Ferrous Alloys: Current Status
Authors: Mahoney Murray , Nelson Tracy W. , Sorenson Carl , Packer Scott
Published: January 2010

Friction stir welding (FSW) offers many potential benefits including reduced distortion, lower cost, no harmful airborne emissions, semi-automated, etc. Although initially developed for Al alloys, considerable work now has been completed to explore the ability of FSW to weld relatively thin (6 mm) ferrous alloys including many alloys of interest to the ship building industry such as HSLA-65. The status of current progress for ferrous alloys is presented offering insight into capabilities and opportunities as well as areas of FSW activity requiring additional improvement. Practical issues of weld penetration depth, gap tolerance, post-FSW mechanical properties, and distortion are addressed. Special consideration will be made to address the ability to friction stir weld 6 mm thick HSLA-65 steel with no/low distortion. Tool materials discussed will include polycrystalline cubic boron nitride (PCBN) and a new composite tool fabricated from PCBN and W-25Re. Last, data will be presented illustrating the complete absence of harmful airborne emissions when welding an austenitic stainless steel.
Casting of Clad Strip by an Unequal Diameter Twin Roll Caster
Authors: Nakamura Ryoji , Sawai Masakazu , Nakamura Ryoji , Watari H. , Kumai S.
Published: January 2010

An unequal diameter twin roll caster which can cast clad strips was devised and assembled. The casting of the clad strip was tried, and fabrication of the clad strip was attained. This twin roll caster was planned for the process saving. The clad strip was assembled directly from AA3003 molten metal and AA4045 molten metal at speed of 20m/min. The Si-diffusion-area between the strips was very narrow, and the interface between the strips was clear. The strips were bonded firmly. The strips were not pealed by the cold rolling and the continuous bending.
Effect of Ultrasonic Melt-Treatment on the Eutectic Silicon and Iron Intermetallic Phases in Al-Si Cast Alloys
Authors: Khalifa W. , Tsunekawa Yoshiki , Okumiya Masahiro
Published: January 2010

The ultrasonic melt treatment is highly efficient in controlling the size and morphology of the alpha-aluminum phase in the Al-Si cast alloys. However, the influence of this treatment on the other phases, namely: the eutectic Si and the Fe-intermetallic phases, has not been thoroughly investigated. This study was undertaken to investigate the effect of ultrasonic melt treatment on the morphology and size of these phases. Four Al-Si cast alloys, 384, 380, 356 and 356 (with 0.8% Fe), were considered in this study. The treatment temperatures were varied from about 100oC above the liquidus temperatures down to the Al-Si eutectic temperature, for different treatment times (4 to 54 s). The results showed that the Si particles are only affected by the ultrasonic vibrations when the eutectic reaction takes place under the ultrasonic field, where more compacted and large Si particles are formed. This limited effect was observed only near to the ultrasonic horn. For other investigated conditions, including treatment in the liquid and semisolid states, the Si particles were obviously unaffected by the ultrasonic treatment. On the other hand, the iron intermetallic phases changed their morphology from large plate-like particles to a more compacted globular form, by the application of ultrasonic vibrations at temperatures up to 10oC above liquidus. Treatments at higher temperatures have limited effect on the morphology of the Fe-intermetallic phases. These observations are general and apply to all the studied alloys.
Precipitation of β' Phase in a Low Cost Beta Titanium Alloy
Authors: Sakamoto Tatsuaki , Hiagaki Yuri , Kobayashi Sengo , Nakai Kiyomichi
Published: January 2010

Precipitation behavior of a metastable β Ti alloy, Ti-6.8Mo-4.5Fe-1.5Al(masss%), during two-step aging has been investigated. Supersaturated β phase after solution treatment decomposes into β+ω phases during the first aging at 300°C for 2ks. β′ phase is observed during the second aging at 500°C for 50s. It is suggested that reverse transformation of the ω phase to β phase during the second aging at 500°C for 50s gives rise to solute-lean and –rich regions in the β phase, and that β′ phase is formed in the solute-rich region. β′ phase being coherent with β phase has larger lattice parameter than β phase. β′ phase acts as nucleation site for α phase, and accelerates the nucleation of α phase.
Strain Rate Effects and Hardening Mechanisms in Ni Base Superalloys
Authors: Nazé Loic , Strudel Jean Loup
Published: January 2010

The mechanical properties of nickel superalloys are related to the spatial distribution of hardening phases, their size and composition, and on the configurations of dislocations introduced by plastic and viscoplastic straining. Heterogeneous plastic flow in relation with dynamic strain aging is examined and synthesized. Dislocations are usually faced with the alternative of shearing or bypassing the ’ phase occupying up to 60 vol.%. Depending on ’ size, several Orowan bypassing mechanisms are observed, alternatively shearing by dislocation pairs or complex configurations involving S-ISF and S-ESF. Variables such as temperature, strain rate and Schmid factor play a decisive role in determining the dislocation configurations which either percolate through the matrix or shear the ’ structure. Various dislocation strategies and microstructures are analyzed and illustrated; they are reviewed critically and summarized in a strain rate versus 1/T mechanism map.
Pulsed Laser Deposition of Thin Coatings: Applications on Biomaterials
Authors: Carradò Adele , Pelletier Hervé , Faerber Jacques , Versini Gilles , Mihailescu Ion N.
Published: January 2010

We report results on Pulsed Laser Deposition (PLD) of ceramic thin films for biomedical applica-tions. The coating of metallic implants with bioceramic thin films (e.g. calcium phosphates, in particular hydroxyapatite) has been proposed as a solution for combining the mechanical properties of the metallic material with the bioactive character of the ceramic layer, leading to a better integration of the entire implant with the newly remodelled bone. Other bioceramics (as e.g. alumina) exhibit a high degree of chemical inertness under physiological conditions, excellent wear resistance, ability to be polished to a high surface finish and excellent hardness as coating. Among the different methods to obtain ceramic coatings that have been widely used so far, PLD was focusing interest due to its versatility and controllability, the aptitude to synthesize and deposit uniform films, with an accurate control of the stoichiometry and crystallinity.
We investigated the micro-structural and mechanical characteristics of PLD bioceramic coatings on metal substrate. Various microscopic observations and mechanical characterisations by nanoindentation and scratch tests were used in order to connect the mechanical response to the microstructure of the coatings. Our studies revealed that the pulsed-laser deposition technique appears to be a competitive candidate in biomedical applications as an extremely versatile technology
Structural Analysis of Sintered Materials Used for Low-Temperature Fuel Cell Plates
Authors: Dudek Agata , Włodarczyk Renata , Nitkiewicz Zygmunt
Published: January 2010

Bipolar plates (BPs) are key components of fuel cells. Functions of materials used for fuel cells include equal distribution of gas fuel and air, conduction of electricity between adjacent cells, heat transfer from the cell as well as prevention of gas leakage and cooldown. Moreover, the material must show particular corrosion resistance in cell’s working conditions. Meeting particular requirements or prevention of the abovementioned situations will enable efficient operation of cells. Due to multifunctional nature of fuel cell plates, choice of materials used for plates is immensely difficult. This paper presents opportunities of application of a new technology of powder sintering for creation of parts for electricity and heat generators. This work also presents analysis of structural and phase-related properties, porosity and strength tests.
Protein Adsorption on Topographically Structured Surfaces: A Mesoscopic Computer Simulation for the Prediction of Prefered Adsorption Sites
Authors: Elter Patrick , Lange Regina , Thull R. , Beck Ulrich
Published: January 2010

In this study the influence of edges and spikes of a topographical nanostructure on the adsorption behavior of proteins at a solid-liquid interface is examined by a computer simulation. An algorithm has been developed, which combines a Finite Differences field calculation with Brownian Dynamics. A (16 nm)3 nano-cube with sharp edges as well as flat faces was chosen as model system and the adsorption of Hen Egg White Lysozyme was investigated. An increased adsorption rate along the edges of a the model cube is reached in the initial adsorption phase under consideration of electrostatic and dispersion interactions. At later times also the surfaces of the cube are covered, if the salt concentration is sufficient to screen the repelling protein-protein electrostatic interaction.
Stress Simulation and Related Bone Ingrowth in Grooves on Implant Surface
Authors: Noyama Yoshihiro , Nagayama Noriyuki , Ishimoto Takuya , Kuramoto Koichi , Sakai Takashi , Yoshikawa Hideki , Nakano Takayoshi
Published: January 2010

Amid increasing numbers of artificial joint implantation surgeries, improving the quality of life (QOL) for patients by accounting for individual variation is a primary concern. Thus, we aim to develop implants designed to optimize the interface between implant and living bone. In particular, for ensuring long-term durability and stability after implantation, we focused on inducement of appropriate alignment for biological apatite (BAp) crystallites and the related collagen (Col) fibers as a bone quality parameter. In this study, we predicted that when stress is applied to bone, the BAp/Col preferential alignment can be formed on the basis of our previous result if osteocytes, which can sense its around stress field, are in an environment that is aligned with the principal stress vector. We tested this idea by introducing grooves with the different angles on the implant surface, considering the principal stress direction. This study finally analyses the effect of stress transmission by a load at the proximal femur on the bone inside and near the grooves by using a mechanical simulation in which groove angles and positions can be changed on the implant surface. Furthermore, we carried out animal experiments using a 2-years-old beagle to examine the effect of grooves in the principal stress direction on the surface in vivo. As a result, bone formation in grooves on the implant surface strongly depends on the grooved angle to the principal stress vector and the grooved position on implants. The new bone preferentially formed inside the grooves parallel to the principal stress direction predicted by three dimensional finite element analysis (FEA) in the proximal area of beagle femur.
Ion Leaching from Implantable Medical Devices
Authors: Eiselstein Lawrence E. , Caligiuri Robert D.
Published: January 2010

Implantable medical devices must be able to withstand the corrosive environment of the human body for 10 or more years without adverse consequences. Most reported research and development has been on developing materials and devices that are biocompatible and resistant to corrosion-fatigue, pitting, and crevice corrosion. However, little has been directly reported regarding implantable materials with respect to the rate at which they generate soluble ions in-vivo. Most of the biocompatibility studies have been done by examining animal implants and cell cultures rather than examining the rate at which these materials leach ions into the body. This paper will discuss what is currently known about the rate at which common implant materials (such as stainless steels, cobalt-chromium alloys, and nitinol) elute ions under in vitro conditions, what the limitations are of such data, and how this data can be used in medical device development.
Validation of a Finite Element Model by Neutron Diffraction for the Prediction of Peen Forming
Authors: Dubois Matthieu , Nady Abdeljalil , Krawitz Aaron , Pirling Thilo , Lodini Alain
Published: January 2010

In the present study, the evaluation of the deformation and the determination of the first order residual stresses in shot peened aluminium plate have been performed by neutron diffraction on the strain imaging instrument SALSA at the Institut Laue Langevin, Grenoble, France, in order to validate a model of finite element analysis permitting to predict the final deformation.
The sample used in this study is a rolled aluminium sheet (Al 2024 T3 alloy) which was clamped in a steel frame and peened following exactly the industrial production process. The first measurements were performed on the sample while it was still clamped. The second set was made after removing it from the frame. For each case, we measured the lattice strains and determined the stress repartition in the three principal directions.
Multi Scale Random Models of Complex Microstructures
Authors: Jeulin Dominique
Published: January 2010

Many nanocomposite materials are obtained by dispersing a charge in a matrix. Due to
the conditions of mixing, the arrangement of the charge usually presents some heterogeneity at
different scales. In order to predict the effective properties of such composites (like the dielectric
permittivity or the elastic moduli), it is necessary to know the properties of the two components
(charge and matrix), and their spatial distribution. To fulfil this project, we developed a general
methodology in several steps: the morphology is summarized by multi-scale random models
accounting for the heterogeneous distribution of aggregates. The identification of models is made
from image analysis. It is then used for the prediction of effective properties by estimation, or by
numerical simulations. Our approach is illustrated by various examples of multi-scale models:
Boolean random sets based on Cox point processes and various random grains (spheres, cylinders),
showing a very low percolation threshold and therefore a high conductivity or elastic moduli for a
low charge content; multi-scale iterations of random media.
Study on the Dimensional Changes and Residual Stresses in Carbonitrided and Ferritic Nitrocarburized SAE 1010 Plain Carbon Steel
Authors: Nan Chun Yan , Northwood Derek O. , Bowers Randy J. , Sun Xi Chen
Published: January 2010

Carbonitriding is a metallurgical surface modification technique that is widely used in the automotive industry to increase surface hardness and wear resistance. Given the problems associated with carbonitriding, such as dimensional distortion, oxidation and non-uniform surface hardness, nitrocarburizing has been proposed as an alternative heat treatment method to improve the surface characteristics. The major advantages of ferritic nitrocarburizing are the minimal dimensional changes and distortion due to the low process temperature at which no phase transformations occur. This increases productivity and product quality, and decreases costs.
The focus of this study was to determine the effects of carbonitriding and ferritic nitrocarburizing processes on the dimensional changes and residual stresses in a steel used for automotive applications. Navy C-ring specimens and prototype stamped parts made from SAE 1010 plain carbon steel were used in the testing. Gas, vacuum and ion ferritic nitrocarburizing processes with different heat treatment parameters were investigated. X-ray diffraction techniques were used for the residual stresses evaluation and surface phase analysis of the specimens.
Friction Stir Welding of Aluminium Based Composites Reinforced with Al2O3 Particles
Authors: Ceschini Lorella , Boromei Iuri , Gambaro C. , Minak Giangiacomo , Morri Alessandro , Tarterini Fabrizio
Published: January 2010

This paper presents the results of microstructural and mechanical characterization of Friction Stir Welding joints of two aluminum-based particles reinforced composites. The composites were FSW in the extruded and T6 heat treated condition. No post-weld heat treatment was carried out on the FSW joints. Hardness, tensile, low-cycle fatigue and impact tests were carried out. Microstructural and fractographic characterization were performed both on the base and FSW material, in order to investigate the effect of the solid-state welding process on the reinforcement particles and aluminum matrix. The FSW produced high quality joints with good microstructural characteristics: the welded zone displayed a refinement of the Al matrix grain size and reinforcement particles, and a better particle distribution. The FSW specimens showed high efficiency, both in the tensile, impact and fatigue tests.
Unconventional Glow Discharge Nitriding of 316L Austenitic Steel
Authors: Frączek Tadeusz , Olejnik Michał
Published: January 2010

This work presents the results of investigations of unconventionally glow-discharge nitrided 316L austenitic steel. The process of nitriding was performed using a variety of variants of sample orientation in glow-discharge chamber. The samples subject to nitriding were located directly on cathode, on the surface isolated from both cathode and anode, in so-called ‘plasma potential’, while the part of the samples with this orientation were additionally covered with screens to supported nitriding process. In order to evaluate the efficiency of various variants of nitriding, the following investigations were conducted: hardness test, element distribution profile within surface layer, metallographic tests, tribological and corrosion resistance tests.
Effect of Milling Parameters on Morphology and Grain Size of WO3 and Al Particles for Fabricating WO3/Al Composites
Authors: Wang Q.W. , Feng Y.C. , Fan Guo Hua , Wang Gui Song , Geng Lin
Published: January 2010

In this paper, the milling process of WO3 and aluminum particles is studied. Influences of rotate rate, milling time and ball-to-powder weight ratio on the morphology and grain size of the particles are studied by scanning electronic microscope and X-ray diffraction techniques. Al particle size decreases firstly and then increases with increasing milling time, while Al grain size decreases gradually as the milling time increases. WO3 particle is distributed uniformly in Al particles after milling for 9h, and has no marked change as further extension of milling time. With increasing the ball-to-powder weight ratio and rotate rate, both particle size and grain size of Al decreases. milling parameters have almost no effect on the grain size of the WO3 particles.
Evaluation of Tools and Cutting Conditions on Carbon Fibre Reinforced Laminates
Authors: Gonçalves Daniel J.S. , Durão Luís Miguel P. , Tavares João Manuel R. S. , Albuquerque Victor Hugo Costa , Marques António Torres
Published: January 2010

The distinctive characteristics of carbon fibre reinforced plastics, like low weight or high specific strength, had broadened their use to new fields. Due to the need of assembly to structures, machining operations like drilling are frequent. In result of composites inhomogeneity, this operation can lead to different damages that reduce mechanical strength of the parts in the connection area. From these damages, delamination is the most severe. A proper choice of tool and cutting parameters can reduce delamination substantially. In this work the results obtained with five different tool geometries are compared. Conclusions show that the choice of an adequate drill can reduce thrust forces, thus delamination damage.
Effect of Calcining Temperature of Ceramic Powders Prepared from TEOS/Boehmite Sol-Gel on Tribological Behavior of Brake Lining Materials
Authors: Lee K.J. , Chen Y.T. , Cheng H.Z. , Jang Jason S.C. , Chang P.C. , Lin S.W. , Chen Y.D.
Published: January 2010

This study is to investigate tribological behavior of brake lining materials by hot pressing commercial friction powders with ceramic powders prepared by TEOS / boehmite sol-gel. The stoichiometric ratios of TEOS / boehmite sol-gel were kept constant but calcinated at different temperature to fabricate different homemade ceramic powders. The various phases of ceramic powders such as γ-Al2O3, δ-Al2O3, θ-Al2O3, α-Al2O3, cristobalite and mullite were formed during the preparation process starting from TEOS / boehmite sol-gel solution. The XRD observations reveal the final compositions of these homemade powders were strongly related to the calcining temperature. The brake lining specimens made from TEOS / boehmite sol-gel calcinated at higher temperature show better tribological performance. The brake lining specimen with α-Al2O3 and mullite which were transformed from TEOS / boehmite sol-gel calcinated at 1300°C shows the most stable friction coefficient and the lowest mass loss during wear tests.