bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser Pulse Simulation of High Energy Transient Thermal Loads on Bulk and Plasma Sprayed W for NFR
Authors: Richetta Maria , Gaudio Pasquale , Montanari Roberto , Pakhomova Ekaterina , Antonelli Luca
Published: November 2016

W is a plasma-facing material candidate for applications in future nuclear fusion reactors (NFR). In this work transient thermal loads of high energy have been simulated by interaction with a single laser pulse. The experiments have been carried out by using the Nd:Glass TVLPS laser working in first harmonic (wavelength λ = 1064 nm); the pulse parameters are: energy E ≈ 8 J, pulse duration ∆t ≈ 15 ns, focal spot size Φ = 200 μm, surface power density on the focal plane I = 1.7 x 1012 W/cm2.The damage produced by the laser pulse on the surface of bulk and plasma sprayed W has been investigated by Scanning Electron Microscopy (SEM) observations. The preliminary results will be presented.
Texture Characterization of Stainless Steel Cladded Layers of Process Vessels
Authors: Rebelo-Kornmeier Joana , Gan Wei Min , Marques M.J. , Batista A.C. , Hofmann Michael , Loureiro A.
Published: November 2016

In this study local texture of process vessels made of carbon steel cladded by protective layers of stainless steel by submerged arc welding (SAW) were investigated by neutron diffraction using the diffractometer STRESSSPEC at FRM 2 (Garching, Germany). Different samples were prepared: as welded and as welded plus relevant industrial heat treatment. Local texture measurements with a gauge volume of 3 x 3 x 2 mm3 of the three cladding layers (at depths of 2 mm, 5 mm and 7.5 mm) for each sample were determined.
Texture results indicated that there exists an annealed cube component in all the studied samples. Based on the measured pole figures at each depth and sample, the calculated orientation distribution functions data were used to calculate the Young's modulus with respect to the main welding directions. The calculated local and bulk anisotropic Young’s modulus in depth is presented and discussed.
The Behaviour of Graphitized Steels in Machining Processes
Authors: Roelofs H. , Renaudot N. , Smolenicki D. , Boos J. , Kuster F.
Published: November 2016

Graphitized steels are claimed to perform excellent in machining processes. They therefore can be considered as environmental friendly alternatives to the widely used Pb-alloyed steels. Due to liquid metal embrittlement and in-situ lubrication Pb improves machinability in a narrow tool-chip interface temperature window corresponding to low machining speeds. Although graphite inclusions are also supposed to generate in-situ lubrication, the mechanism and the corresponding optimum working zone is not very clear. The present work applies a new test methodology (including in-situ tribology, analysis of material flow and chip formation, optimum working zone analysis) to investigate the effects of graphite inclusions on turning and drilling operations. A Pb-alloyed low carbon free-cutting steel and Pb-alloyed case hardening steel were used as reference steels.
A New Approach for the Spectroscopic Detection of Different pH-Values
Authors: Rogge Christian , Zinn Steffen , Schneider Sylvio , Francini Roberto , Prosposito Paolo , Foitzik Andreas H.
Published: November 2016

The objective of the present work was the development of a micro-pH meter for the determination of the pH value within bioreactors with a volume of up to 200 μl in total. Two different prototypes of optodes were designed and tested. In a first approach spectroscopic analysis of bromothymol blue in a micro-sized-channel structure was carried out utilizing glass fibers, enabling measurements in sample volumes down to the range of picoliters. In a second approach a different illumination system consisting of a RGB-sensor and a LED light source was used. Phenol red was successfully applied as the pH indicator for this setup.
Influence of Long Heat Treatments on Hardness and Tribological Behaviour of HVOF Sprayed WC-CoCr and Cr3C2-25NiCr Coatings
Authors: Rovatti L. , Gariboldi Elisabetta , Lecis N. , Mondora L. , Mondora G.A.
Published: November 2016

Thermally sprayed tungsten and chromium carbide-based coatings are widely applied in several industrial applications and in harsh environments where the tribological resistance is required, such as in many components for oil &gas or petrochemical industries. The microstructural stability of the coatings is a key feature for improving the working life of components exposed at high temperature during service. While WC and Cr3C2-based coatings are known to be suitable materials for low and high temperature, respectively, there is the need to know their behavior at intermediate temperature to make a proper selection in these cases. In the present study two different coatings, WC-10Co-4Cr and Cr3C2-25NiCr, were deposited by HVOF and analyzed comparing the as received conditions with the aged conditions after isothermal treatments. The effect of aging at temperatures in the range 250-400°C was evaluated focusing on hardness behaviour in function of aging time and temperature. Furthermore, wear tests measurements were performed, before and after aging, for evaluating the exposure effect on the tribological properties of both coatings.
Hot Deformation Behavior and Stability Criteria of WE54 Magnesium Alloy
Authors: Rieiro Ignacio , Carsí Manuel , Ruano Oscar
Published: November 2016

A precise description of the hot deformation behavior as well as determination of the stability conditions as influenced by temperature and strain rate is fundamental for the simulation of metal forming processes. In this work, a revision of various stability criteria of magnesium alloy WE54 is conducted. The study corresponds to own work and that of Lentz et al. and is based on compression tests at high temperature and high strain rates. Stability and processing maps were obtained using a variety of stability criteria, some based on the efficiency parameter η and others on the strain rate sensitivity parameter, m. This parameter is usually determined by fitting the curves strain rate, ε, versus stress, σ, by means of a potential equation named “power law” or by a polynomial of second or third degree, and calculating the slope of the logarithmic curve at each point using successive derivatives. This procedure is compared with one developed by us where all experimental points are fitted to a single hyperbolic sine equation of Garofalo type and then m and η are calculated for each ε and T using this equation. The maps obtained by one or the other method differ considerably. The predictions of these maps were contrasted with microstructural observations and conclusions on the deformation behavior of the alloy are reached.
Development of a 2.25%Cr Steel P23 Reinforced with Micro/Nano-Carbide Particles Produced by Self-Propagating High-Temperature Synthesis
Authors: Carsí Manuel , Jiménez José A. , Gomez-Mitxelena Xabier , Ruano Oscar
Published: November 2016

In the present work, 1 wt.% of (Ti,Nb)C carbide particles prepared by self-propagating high temperature synthesis (SHS) were introduced into a melt of a conventional P23 steel to obtain a reinforced material with improved creep properties. The as-cast material showed a eutectic type microstucture, indicating partial dissolution of these carbides in the melt. Inside the dendritic regions, a bainitic/martensitic structure similar to that of the unreinforced material was present. A significant refinement of the prior austenitic grain size was revealed in the reinforced material. Brinell hardeness measurements reveal an increase of hardness in the reinforeced material due to the addition of the carbides. High strain rate compression tests were perfomed at temperatures in the range 950 and 1250oC to determine the optimum forming conditions. Stability maps for a wide range of temperatures and strain rates were drawn. The optimum temperature for the reinforced steel is about 77 K higher than for the non-reinforced steel.
Physical Modelling of Metallurgical Processes
Authors: Saternus Mariola , Pieprzyca Jacek , Merder Tomasz
Published: November 2016

Today physical modelling is a commonly used tool in modelling metallurgical processes. It can be applied both in steel metallurgy and non-ferrous metals metallurgy processes. It gives the opportunity to determine the hydrodynamic conditions of the processes. Although, the flow of mass and gas is not totally presented by such modelling, this kind of research is very often and willingly used. That is because it is really difficult to conduct experimental research in industrial conditions. Typically water is used as a modelling agent, so the physical modelling is not as expensive as the one carried out in industrial conditions.
To obtain representative research from physical modelling the physical models have to be built according to the strict rules coming from the theory of similarity. The results obtained from the experimental test on the physical model, after verification, can be transferred to the real conditions.
The article shows the obatined results coming from physical modelling of the steel production process. In the Institute of Metals Technologies of Silesian University of Technology the appropriate test stand was built to simulate the steel flow and mixing in the ladle. The visualization results have been presented. To simulate processing condition during aluminium refining additional test stand was also built. The exemplary results have been shown for different flow rate of gas, rotary impeller speed and different shapes of impellers. All presented results have been discussed and presented for the perspectives of further research.
Effects of Particle Size on Fabrication of Al-TiO2 Functionally Graded Materials by Centrifugal Mixed-Powder Method
Authors: Sato Hisashi , Maeda Junya , Yamada Motoko , Watanabe Yoshimi
Published: November 2016

As one of processing methods of functionally graded materials (FGMs), centrifugal mixed-powder method has been proposed. The centrifugal mixed-powder method is the casting process combined of centrifugal casting and powder metallurgy. This processing method has advantage that fine ceramics-particles, whose wettability with matrix melt is low, can be compounded into metallic material. However, effects of particle size on microstructure and mechanical properties of the FGMs fabricated by the centrifugal mixed-powder method are unclear. In this study, two kinds of Al-TiO2 FGMs rings are fabricated by the centrifugal mixed-powder method. One contains TiO2 particles having similar diameter with Al matrix particles (hereafter, small different-size (SD) TiO2 particles), and the other one compounds TiO2 particles with much smaller diameter than Al matrix particles (hereafter, large different-size (LD) TiO2 particles). In case of the Al-TiO2 FGMs ring containing SD-TiO2 particles, the TiO2 particles are homogeneously dispersed in Al matrix on outer surface of the ring. On the other hand, the TiO2 particles in the Al-TiO2 FGMs ring with LD-TiO2 particles are distributed along grain boundary of Al matrix. Moreover, Vickers-hardness and wear resistance around outer surface of the Al-TiO2 FGMs ring containing the SD-TiO2 particles is higher than that of the Al-TiO2 FGMs ring with LD-TiO2 particles. Since Al particles in the mixed-powder with LD-TiO2 particles are surrounded by the TiO2 particles, the Al particles can be hardly melted by heat of molten Al at casting process. As a result, the Al-TiO2 FGMs ring with LD-TiO2 particles has low hardness and wear resistance. Therefore, it is found that TiO2 particles having similar diameter with Al matrix particles are more suitable for fabrication of the Al-TiO2 FGMs rings.
Usability of Ti6Al4V Powder via Hydride-Dehydride Process for Selective Laser Melting Process
Authors: Sato Naoko , Ito Masaki , Izumida Takayuki , Shimizu Toru , Nakano Shizuka
Published: November 2016

Spherical powders via gas atomization etc. are recommended for use in SLM, however, the spherical powders are expensive and able to make in limited types of metal materials. Using non-spherical powder in SLM are capable of applying SLM to cheap part production and diversify powder materials for SLM. In this paper, to study the feasibility of using Ti6Al4V milled powder via hydride-dehydride method for SLM, characteristics of powders, powder bed performances, and SLM fabricated samples made from gas atomization powder and milled powder were analyzed and compared. The milled powder which added a fumed silica as a lubricant were also analyzed. In the results, flow and packing characteristics of the milled powder are lower than the gas atomized one. The characteristics of the milled powder are improved by adding fumed silica as lubricant, and had comparable characteristics to the gas atomized one. Microstructure of the SLM fabricated samples has a comparable size and morphology regardless of powders. Hardness of the SLM fabricated sample made from milled powder are larger than that of it made from gas atomized powder, owing to solid solution hardening by oxygen.
Influence of Corrosive Conditions on the Mechanical Performance of Flow Drill Screw Joints between Light Metals
Authors: Scholz Carmen S. , Kopp Gundolf , Friedrich Horst E.
Published: November 2016

In this paper, the influence of corrosive conditions on the mechanical performance of Flow Drill Screw (FDS) joints is investigated in greater detail. Different combinations of light metals such as aluminium or magnesium alloys and high strength/stainless steel served as the test material. The joint strength of FDS joints, under quasi-static and cyclic loading, was measured before and after six weeks’ of corrosion climate change testing. Furthermore metallographic sections of the samples were compared in order to evaluate the stage of surface, galvanic and crevice corrosion. To classify the effect of progressing corrosion on the mechanical properties of FDS joints, the following factors are taken into account: corrosion resistance of the materials, joining parameters and the geometry of the joint. For all material combinations there is an apparent change in both the fatigue strength and the failure behaviour after corrosion testing.
Calculation of the Stress Interaction between Dislocation Pile-Ups in Neighbouring Misoriented Grains
Authors: Schouwenaars R. , Ortiz A. , Jacobo V. H.
Published: November 2016

During the early stages of the plastic deformation of a polycrystal, dislocations can pile-up against grain boundaries. Experimental results on large-grained materials have provided excellent verification of this phenomenon. Such a pile-up may activate dislocation slip in the neighbouring grain. Whether this occurs depends on the misorientation between the grains and the resolved shear stresses in the affected grain. Several approximate criteria have been proposed to predict the occurrence of this mechanism. Here, the problem will be assessed directly by calculating the Peach-Köhler force produced by a single dislocation pile-up in one grain on all the possible slip systems in the neighbouring grain, in combination with the effect of the applied external stress as obtained through calculation of the Schmid factor. It will be seen that the problem is significantly more complex than what is generally assumed in basic explanations of the Hall-Petch effect: highly localised stress concentrations are generated for certain misorientations, which are capable of punching out small dislocation loops which may then propagate into the neighbouring grain.
Development of Joining Method between Zircaloy and SiC/SiC Composite Tubes by Using Diode Laser
Authors: Serizawa Hisashi , Asakura Yuuki , Motoki Hirotaka , Tanigawa Daisuke , Tsukamoto Masahiro , Park Joon Soo , Kishimoto Hirotatsu , Kohyama Akira
Published: November 2016

Silicon carbide fiber reinforced silicon carbide composite (SiC/SiC composite) is expected as a potential replacement of the current Zircaloy fuel cladding in the light-water reactor because of its many superiorities, where it is necessary to develop the end-cap seal of SiC/SiC composite cladding. In this research, the applicability of diode laser irradiation for joining between Zircaloy and SiC/SiC composite tubes was examined based on the caulking method. As the method for fitting two tubes, the screw cutting was conducted for the inner face of Zircaloy tube and the outer surface of SiC/SiC composite. In addition, as a method to improve the joinability of Zircaloy and SiC/SiC composite, titanium nanopowder was inserted into a gap between two tubes. The laser beam irradiation was circumferentially applied to the outer surface of Zircaloy tube. Although the mechanical caulking joint was successfully produced, the airtightness was insufficient for the end-caps of SiC/SiC composite cladding. However, the good adhesion between Zircaloy and SiC/SiC composite was partially produced as the result of the generation of all proportional solid solution between titanium and zirconium. Namely, it can be concluded that the circumferential diode laser irradiation with inserting titanium nanopowder between Zircaloy and SiC/SiC composite tubes would have a good potential for producing the caulking joint of two tubes.
Effect of Heat Treatment on the Microstructure Evolution of Ti-6Al-3Sn-3Zr-3Mo-3Nb-1W-0.2Si Titanium Alloy
Authors: Song Xiao Yun , Zhang Wen Jing , Ma Teng , Ye Wen Jun , Hui Song Xiao
Published: November 2016

Ti-6Al-3Sn-3Zr-3Mo-3Nb-1W-0.2Si (BTi-6431S) alloy is a novel two-phase high temperature titanium alloy for short-term using in aerospace industry up to 700°C. The effects of heat treatment on the microstructure evolution of BTi-6431S alloy bar were investigated through optical microscopy (OM), X-ray diffraction (XRD), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM). The results show that solution treatment in β region at 1010°C followed by water quenching results in the formation of orthorhombic martensite α′′ phase, while air cooling leads to the formation of hexagonal martensite α′ phase. When solution-treated in α+β phase field at temperatures from 900°C to 980°C following by water quenching, the content of primary α phase decreases with the increase of heat treatment temperature. For the alloy subjected to identical heat treatment, the content of Al in α phase is much higher than that in β phase, while the contents of Nb, Mo and W elements in α phase are much less than those in β phase.
Three-Dimensional Dynamic Explicit Finite Element Analysis of Charpy Impact Test
Authors: Takashima Yasuhito , Handa Tsunehisa , Minami Fumiyoshi
Published: November 2016

Dynamic explicit finite element (FE) analysis of the Charpy impact test was conducted in this study to investigate the inertial effect on the stress field ahead of the V-notch in a Charpy specimen. The deformation behavior of the Charpy specimen and the constraint effect on the stress field in the plastic zone near the V-notch were numerically simulated using three-dimensional FE analysis, while considering the contact of the specimen with the striker and anvil. The effect of the strain rate on the flow stress and the increase in temperature during impact loading were included in the dynamic analysis. This analysis shows that the impact load exhibits oscillation and the contact stiffness between the specimen and the striker affects the oscillation of the impact load.
The analysis was validated by comparison with experimental results obtained using an instrumented Charpy impact testing machine, which measured the impact load and the load point displacement. The oscillation of the load–time curve was recorded. The magnitude and period of the peak inertia load obtained by the FE analysis were almost consistent with the experimental results. The contact stiffness between the specimen and the striker affected the stress field near the V-notch in the specimen. This indicates that the stress field in the Charpy specimen should be analyzed by the dynamic analysis procedure considering the contact stiffness based on the Hertzian contact theory.
Dispersion of CNTs in Selective Laser Melting Printed AlSi10Mg Composites via Friction Stir Processing
Authors: Du Zheng Lin , Tan Ming Jen , Guo Jun Feng , Wei Jun , Chua Chee Kai
Published: November 2016

The superior elastic modulus, stiffness and wear resistance of particulate-reinforced metal composites (MMCs) have drawn much attention in various industries ranging from defence, aerospace and automobile industries. Here, friction stir processing (FSP) has successfully dispersed carbon nanotubes (CNTs) and significantly reduced cavities in selective laser melting (SLM) fabricated AlSi10Mg-CNTs composites. Further grain refinement, was achieved via FSP with the addition of CNTs. This is mainly attributed to the dynamic recrystallization and Zener pinning effect. The addition of CNTs to AlSi10Mg resulted in significant improvement in hardness of SLM fabricated aluminium composites. However, FSP of these samples resulted in reductions in the Vicker’s microhardness. This could be due to the dissolution of hardening precipitates and the absences of fine dendritic network present in SLM fabricated parts.
Effect of Tempering on Microstructure and Creep Properties of P911 Steel
Authors: Tkachev Evgeniy , Odnobokova Marina , Kipelova Alla , Belyakov Andrey , Kaibyshev Rustam
Published: November 2016

The microstructure and creep properties of a P911-type steel normalized at 1060°C and then subjected to one-step tempering at 760°C for 3 h or two-step tempering at 300°C for 3 h + 760°C for 3 h were examined. The transmission electron microscope (TEM) observations showed that the tempered martensite lath structure (TMLS) with a lath thickness of 340 nm evolved after both tempering regimes. High dislocation densities of 3×1014 or 5×1014 m-2 retained after one-and two-step tempering respectively. M23C6 carbides with a mean size of 120 nm and V-rich MX carbonitrides having a “wing” shape with an average length of about 40 nm precipitated on high-and low-angle boundaries and within ferritic matrix, respectively. A number of Nb-rich M(C,N) carbonitrides with a mean size of 20 nm precipitated on dislocations during low temperature tempering. The creep tests were carried out under constant load condition at 650°С at applied stresses of 100 and 118 MPa. Analysis of creep rate versus time curves showed that the use of two-step tempering decreases the minimum creep rate providing an increase in the creep strength in long-term conditions.
Ti-Cu-Based Amorphous Powders Produced by Ball-Milling
Authors: Tomolya Kinga
Published: November 2016

The effect of Ni or Zr addition to Ti-Cu alloy was studied on the microstructure evolution during mechanical milling regarding to dependence of the amorphous transformation on the various composition elements. The microstructure of initial crystalline alloys and the remained phases after few hours of milling were investigated. The milling process lasted to the full amorphization of the powders. The results show that amorphous Ti48Cu42Ni10 and Ti48Cu42Zr10 powders are obtained after 13 h and 14 h of milling.
Effect of а Number of Transition Metals on the Cohesive Properties of Cr-Ni-Base Alloys
Authors: Butrim V.N. , Razumovskiy V.I. , Beresnev A.G. , Trushnikova A.S. , Razumovskii I.M.
Published: November 2016

We used the results of ab initio calculations to improve the high temperature mechanical properties of a Cr-Ni-base alloy (Cr-33Ni-2W-0,3Ti-0,3V, wt.%) (alloy I) with two-phase α - γ microstructure. It was established that γ – phase in Cr-Ni-base alloy (I) plays a key role in the processes of plastic deformation. By analogy with Ni-base superalloys the bulk and grain boundaries cohesion in γ – phase of the Cr-Ni-base alloy (I) were strengthened by adding a package of the “low alloying” elements (Zr, Hf, Nb, Ta) (alloy II) chosen in accordance with our theoretical predictions. We further investigated an influence of a sum (Ta, Nb, Hf, Zr) like the low alloying additions on the mechanical properties of Cr-Ni-base alloy (I). The results of mechanical testing revealed a significant strengthening of the alloy (II) in comparison with (I) at the temperature 1080 oC in accordance with our predictions. We also investigated the microstructure’s peculiarities of the alloys (I) and (II).
Shock-Induced Reaction Characteristics of an Al/Ni Composite Processed via Accumulative Roll-Bonding
Authors: Ji Cheng , He Yong , Wang Chuan Ting , He Yuan , Xiong Wei , Zhang Xian Feng , Zhou Jie , Gu Lei , Yang Xiang Liang , Pan Xu Chao
Published: November 2016

Al/Ni composite is widely recognized as a member of multifunctional energetic structural materials (MESMs), which could release energy due to exothermic chemical reactions initiated under shock loading conditions. In this study, an Al/Ni composite was produced via accumulative roll-bonding (ARB) process up to four cycles. The shock-induced reaction behavior of the material was investigated by means of a quasi-sealed test chamber. The results demonstrated that the Al/Ni composite fabricated by ARB underwent chemical reaction when impacted onto steel target. The energy released by reaction caused significant pressure rise inside the quasi-sealed chamber. It was shown that the amount of energy increased with the increasing of impact velocity. The results of this study represented the potential of Al/Ni composite processed by ARB as reactive fragments.
Martensitic Transformation and Crystal Structure Characterization of Ni-Fe-Ga-Co Ferromagnetic Shape Memory Alloys
Authors: Jiang Pan , Bai Jing , Wei Pu , Han Shuang Ji , Yang Mei Jie , Teng Fei , Wang Xin Li , Zhao Xiang
Published: November 2016

In this paper, the martensitic transformation temperature, the microstructure and the crystal structure of the complicated martensitic phases of Ni56-xFe19Ga25Cox (x =0, 1.5, 3, 4.5, 6) alloys were investigated by DSC, XRD, SEM and TEM techniques. DSC results show that the martensitic transformation temperature Tm, which is above the room temperature, decreases with the increasing Co content. The microstructure of the Ni56-xFe19Ga25Cox (x =0, 1.5, 3, 4.5, 6) alloys is composed by the martensitic lath and randomly distributed γ phase. The 6M+14M mixed modulated martensite and the γ second phase were detected in the Ni53Fe19Ga25Co3 alloy by XRD and TEM tests.
Temperature Field Evolution during Flash Butt Welding of Railway Rails
Authors: Weingrill Leonhard , Krutzler Jörg , Enzinger Norbert
Published: November 2016

Flash butt welding (FBW) of railway rails was investigated in this work. For this purpose samples of R260 rail steel and 60E1 profile were instrumented and subsequently welded on a Schlatter GAA 100 welding machine under industrial conditions. The intention is to gain in depth process knowledge by more accurately depicting thermal cycles for an entire welding sequence in the immediate proximity of the weld as well as in the heat affected zone (HAZ). A detailed characterization of the single stages of the heat up phase of the process is important. Additionally, the secondary welding voltage was measured simultaneously during the experiments to characterize the transient heat input. Moreover, these data were used in the analysis of the temperature signals to better cope with electrical interferences.
Additionally, a finite element (FE) model of this FBW process was developed in the present work. Its implementation and solution is realized with the help of ESI’s FE-software SYSWELD. A strong coupled thermo-electrokinetical and metallurgical calculation routine was used. The model comprises the transition resistance at the welding surfaces as the main heat source to the process. Temperature dependent material properties and a corresponding metallurgical model based on an experimental CCT diagram of the rail steel R350HT are implemented in the simulation as well.
Processing and Thermoelectric Properties of New Si-/ Se-/ Sn-Based Intermetallics
Authors: Wunderlich Wilfried , Sato Masashi , Matsumura Yoshihito
Published: November 2016

Global warming is the driving force for developing new functional thermoelectric generators based on new materials which contain at least one of the elements Si, Se, or Sn. We describe four processing methods and their characterization by SEM and thermoelectric properties. The earth-abundant Mg2Si requires the method of cyclic hydrogen loading, which has two advantages: It suppresses the oxide formation, and promotes the driving force for formation of the intermetallic phase. While the clathrate BaCuSi and the Half-Heusler alloy (TiZr)NiSn, as most intermetallic alloys, can economically be produced by arc-melting, the Se-alloys CuTiSe and CuFeSe need to be processed by the powder-in-tube method and their Seebeck-voltage measurements up to +/- 0.04 mV/K and output power of 4 μW at ΔT= 400 K are reported here for the first time.
Further Study on the Effect of Environment on Fatigue Crack Growth Behavior of 2000 and 7000 Series Aluminum Alloys
Authors: Yamada Ryuichi , Itoh Goroh , Kurumada Akira , Nakai Manabu
Published: November 2016

The 7000 series alloys have the highest strength in the aluminum alloys, but lower fatigue properties than 2000 series alloys. Thus, 7000 series alloys are not applied to a large proportion of the aircraft components. However, the mechanism for this has not been elucidated yet. In humid air, hydrogen embrittlement based on intergranular cracking has been known to occur in 7000 series alloys. To date, in order to explain the difference in the fatigue crack growth behavior in the two series alloys, the effect of the test environment on the fatigue crack growth of the two series alloys has been investigated in this study. A 7075-type as well as 2024-type alloy with relatively coarse equi-axed grains was T6-tempered and subjected to fatigue crack growth test in humid and dry environments. Crack growth rate at low ΔK level seemed to be larger in the 7075-type alloy than the 2024-type alloy in the humid air, when assessed by means of gradually decreasing K method. In order to clarify this result, crack growth rate of the two alloys was assessed by means of gradually increasing K method as well as decreasing K method. Crack growth rate of the 7075-type alloy in moist air was concluded to be the largest in consistent with the previous study. Thus, the large fatigue crack growth rate of the 7075-type alloy is attributable to hydrogen embrittlement.
Regularities of Microstructure Evolution and Strengthening Mechanisms of Austenitic Stainless Steels Subjected to Large Strain Cold Working
Authors: Belyakov Andrey , Odnobokova Marina , Shakhova Iaroslava , Kaibyshev Rustam
Published: November 2016

The deformation microstructures and their effects on mechanical properties of austenitic stainless steels processed by cold rolling at ambient temperature to various total strains were studied. The cold working was accompanied by the development of strain-induced martensitic transformation because of meta-stable austenite at room temperature. The strain-induced martensitic transformation and deformation twinning promoted the grain refinement during cold rolling, leading to nanocrystalline structures consisting of a mixture of austenite and martensite grains with their transverse grain sizes of 50-150 nm containing high dislocation densities. The rolled samples experienced substantial strengthening resulted from high density of strain induced grain/phase boundaries and dislocations. The yield strength of austenitic stainless steels could be increased to 2000 MPa after rolling to total strains of about 4. The martensite and austenite provided almost the same contribution to overall yield strength. The dislocation strengthening was much higher than the grain boundary strengthening at small to moderate strains of about 2, whereas the latter gradually increased approaching the level of dislocation strengthening with increasing the strain.
Effect of Friction Stir Welding on Microstructure of a 5024 Alloy
Authors: Yuzbekova Diana , Kulitskiy Vladislav , Mogucheva Anna , Kaibyshev Rustam
Published: November 2016

Influence of friction stir welding (FSW) on microstructure of an Al-4.57Mg-0.35Mn-0.2Sc-0.09Zr (wt. pct.) alloy was studied. Following parameters of FSW were used: the rotation speeds of 500, 650 and 800 rpm, the traverse speed of 75 mm/min and the tilt angle of 2.5°. Defect-free welds were obtained using all these parameters. FSW leads to the formation of fully recrystallized microstructures with average grain sizes less 2 μm and a moderate dislocation density of ~1013 m–2 in the stir zone. No evidence for abnormal grain growth was found in the heat affected zone of the weld. The nanoscale Al3(Sc,Zr) dispersoids coarsened to 21 nm but retained coherent interfaces and cube-cube orientation relationship with the matrix.
Effects of Hydraulic Pressure on Shape Accuracy of Drawn Circular Cups during Micro Hydro Deep Drawing
Authors: Luo Liang , Jiang Zheng Yi , Wei Dong Bin , Sato Hideki , Furushima Tsuyoshi , Manabe Kenichi
Published: November 2016

Micro hydro deep drawing is a promising technology to fabricate micro metal products with complex 3D shapes. However, the size effects in the micro hydro deep drawing become considerable and significantly influence shape accuracy of drawn cups. In this study, a Voronoi micro scale simulation model was developed to consider the size effects of SUS304 foils. A surface layer model was additionally applied in the simulation to further explain the size effects. The micro hydro deep drawing experiments were conducted with annealed SUS304 foils and the drawn cups were examined. The wrinkling phenomenon was generally aggravated with the hydraulic pressure. Simulation results also show that the high hydraulic pressure does not improve the shape accuracy of the drawn cups as that in the normal scale hydro deep dawning process does. The simulation results are in accordance with the experimental results.
Kinetics of Microstructure Refinement in Titanium Alloys during Deformation
Authors: Zherebtsov Sergey , Ozerov Maxim , Kimova Margarita , Salishchev Gennady
Published: November 2016

The effect of various factors on the kinetics of microstructure evolution in commercial-purity titanium and two-phase Ti-6Al-4V alloy during deformation was studied. The kinetics of microstructure refinement can be raised via intensification of deformation twinning. In two-phase titanium alloys the kinetics of spheroidization can be increased considerably by decrease in the thickness of initial α lamellae. The influence of interphase boundaries energy on deformation behavior was discussed with respect to Ti-6Al-4V and Ti/TiB alloys.
Microstructure and Mechanical Properties of Medium Manganese Steel Plate with High Strength and Toughness
Authors: Zou Ying , Xu Yun Bo , Hu Zhi Ping , Yang Xiao Long , Tan Xiao Dong , Yu Shi Chuan , Liu Hui , Yu Yong Mei
Published: November 2016

An intercritical annealing process was applied to a medium manganese steel plate (Fe-0.01C-5.3Mn-1.53Si) after the thermo-mechanical controlled processing (TMCP) and ultrafast cooling (UFC). The microstructures were observed by scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD), electron probe micro-analyzer (EPMA) and transmission electron microscopy (TEM). The retained austenite was measured by XRD and mechanical properties were measured by uniaxial tensile and impact tests. The influence of different annealing temperature was compared and the relationship between microstructures and mechanical properties was investigated. Results showed that the microstructures of the medium manganese steel plate were characterized by ultrafine grained lath-like ferrite and retained austenite and the excellent mechanical properties could be obtained at the annealing temperature of 640°C for 5 h. The volume fraction of the retained austenite reached up to 21%, which could significantly increase the elongation compared with the traditional steel plate. The mechanical property results revealed that the steel possessed adequate ultimate tensile strength of 865MPa and excellent impact energy of 121J (-20°C). The outstanding combination of strength and toughness indicates that the steel has a bright application prospect.
Evaluating Athletic Performances with a Real Time Location and Tracking System
Authors: Milici Stefano , Esposito Ambra , Staderini Enrico M.
Published: November 2016

The precision in localization of the UBISENSE Real Time Location System was assessed for evaluating the possibility of using the system in the detection of movements and position of athletes on the field during sport performance. The system was implemented in an indoor lab space measuring 11 by 7 meters. Four sensors were installed on the roof at a height of 3 meters above floor. Various sampling rates were used with a single location tag. UBISENSE is using UWB localization technology based on the triangulation of time of arrivals of UWB pulses at the different
antenna sensors. Precision varied in position and speed determination being position resolution in the range of 15 to 50 cm while speed precision was in the figure of 6% at slow actual speed of 0.18 m/s up to 20% at fast speed of 1 m/s. This was mainly due to sampling frequency in the location system. In conclusion, as long as speed of the athlete is not at stake, the position can be measured with quite good resolution and sampling frequency so to permit the evaluation of sport performances of the athlete during the exercise or activity. A very attractive feature of the system is that the athlete must be tagged with a very low-weight and quite comfortable active tag which, on the contrary to video tracking systems, doesn’t need to remain in the field of view.
Miniaturized Flow-Through Bioreactor for Processing and Testing in Pharmacology
Authors: Böhme Andrea , Radke Lars , Schütze Felix , Schneider Sylvio , Liebscher Thilo , Sauer Sabine , Santo Loredana , Quadrini Fabrizio , Hummel Michael , Giese Christoph , Frohme Marcus , Foitzik Andreas H.
Published: November 2016

Conventional Bioreactor systems for cultivating cells in Life Science have been widely used for decades. An in vitro cell cultivation bioreactor should reliably and reproducibly mimic the in vivo microenvironment of the cultured cells. Normally, mammalian cell cultures are performed in conventional bioreactor devices such as culture flasks and culture-dishes. However, these tools have fundamental limitations due to being inappropriate for high throughput screening and consume a considerable amount of resources and time [1]. Therefore, there is a trend towards miniaturization, disposables and even micro platforms that fulfill increasing demands strongly aiming for production and testing of novel pharmaceutical products. Here we present the development and manufacture of a disposable miniaturized flow-through bioreactor system that can be produced in large numbers at low costs.
nanoporous hollow fibers are located at the fluidic sources and drains of the miniaturized bioreactors and retain cells. The necessary mixture of oxygen and carbon dioxide is provided via diffusion through a semi-permeable membrane. Fluidic connections allow the continuous feeding of the cells adding nutrient solution at constant rates at the inlet of the micro bioreactor and removing the solution at the same rate at the outlet. This medium can be collected and used for subsequent analysis. Different designs and concepts for such bioreactors were carried out with varying numbers of plates, and integrated or joined miniaturized reactor chambers. First tests show full technical and biological functionality, cells could successfully be cultivated at high viability rates for some days.
Thermal Conductivity of Cubic Boron Nitride (cBN) Particle Dispersed Al Matrix Composites Fabricated by SPS
Authors: Mizuuchi Kiyoshi , Inoue Kanryu , Agari Yasuyuki , Tanaka Motohiro , Takeuchi Takashi , Tani Jun Ichi , Kawahara Masakazu , Makino Yukio , Ito Mikio
Published: November 2016

Cubic boron nitride (cBN) particle-dispersed-aluminum (Al) matrix composites were fabricated from the powder mixture composed of cBN, pure Al and Al-5mass% Si alloy in liquid and solid co-existent state by spark plasma sintering (SPS) process. Al/cBN composites were well consolidated by heating at a temperature range between 798 K and 876 K for 1.56 ks by SPS. Microstructures of the composites produced were examined by scanning electron microscopy and the reaction between the cBN particle and the Al matrix was not detected. The relative packing density of the Al/cBN composite was higher than 99 % in a volume fraction range of cBN up to 45 %. The thermal conductivity of the composite increased with increasing the cBN content in the composite in a volume fraction range of cBN between 35 and 45 vol. %. The highest thermal conductivity of 305 W/mK was obtained for Al matrix composite containing 45 vol.% cBN particles.
Lightweight Sandwich Structures in Innovative Vehicle Design under Crash Load Cases
Authors: Brückmann Simon M. , Friedrich Horst E. , Kriescher Michael , Kopp Gundolf , Gätzi Roman
Published: November 2016

On modern vehicles, the demand is made to be in every respect as efficient as possible. A technical method to increase energetic efficiency is to reduce the vehicle mass through the implementation of lightweight construction measures. The energy consumption decreases by that and the vehicle dynamics behavior of conventionally and alternatively respectively electrically powered vehicles increases.
In the department Lightweight and Hybrid Design Methods of the Institute of Vehicle Concepts in Stuttgart in collaboration with 3A Composite Core Materials, a method which allows to realize sandwich structures for automotive structural applications analytically and conceptually, is developed. The development method based on material and component testing and material values would be determined at different loads, for example in pressure and in-plane tests. These values are transmitted into the analytical determination of so called failure mode maps to derive appropriate sandwich structures. With novel sandwich structures the objectives of high structural stiffness and strength are tracked, as well as a high level of energy absorption potential. By function integrating the potential of lightweight construction, depending on the energy absorption per structural weight, can be further increased. Accompanying tests on generic structures are made to validate the failure behavior. Also the influence of core material on the deformation behavior is examined. The results from the tests are transferred to a vehicle front structure of a planned lightweight vehicle of class L7E called "Safe Light Regional Vehicle" (SLRV). The behavior of the structure is examined in static and dynamic tests. The energy absorbing capacity can be further increased by geometric optimization and the use of different core materials.
The research on sandwich materials is part of the research project Next Generation Car (NGC) of the DLR and represents in terms of the new vehicle concept SLRV in sandwich design a novel vehicle concept of this joint project.
In Vitro Assessment of Hydroxyapatite Coating on the Surface of Additive Manufactured Ti6Al4V Scaffolds
Authors: Chudinova Ekaterina , Surmeneva Maria , Koptioug Andrey , Savintseva Irina V. , Selezneva Irina I. , Skoglund Per , Syrtanov M. , Surmenev Roman
Published: November 2016

Custom orthopedic and dental implants may be fabricated by additive manufacturing (AM), for example using electron beam melting technology. This study is focused on the modification of the surface of Ti6Al4V alloy coin-like scaffolds fabricated via AM technology (EBM®) by radio frequency (RF) magnetron sputter deposition of hydroxyapatite (HA) coating. The scaffolds with HA coating were characterized by Scanning Electron microscopy, X-ray diffraction. HA coating showed a nanocrystalline structure with the crystallites of an average size of 32±9 nm. The ability of the surface to support adhesion and the proliferation of human mesenchymal stem cells was studied using biological short-term tests in vitro. In according to in vitro assessment, thin HA coating stimulated the attachment and proliferation of cells. Human mesenchymal stem cells cultured on the HA-coated scaffold also formed mineralized nodules.
Continuous Modeling of Dislocation Cores Using a Mechanical Theory of Dislocation Fields
Authors: Gbemou Kodjovi , Raulot Jean Marc , Taupin Vincent , Fressengeas Claude
Published: November 2016

A one-dimensional model of an elasto-plastic theory of dislocation fields is developed to model planar dislocation core structures. This theory is based on the evolution of polar dislocation densities. The motion of dislocations is accounted for by a dislocation density transport equation where dislocation velocities derive from Peach-Koehler type driving forces. Initial narrow dislocation cores are shown to spread out by transport under their own internal stress field and no relaxed configuration is found. A restoring stress of the lattice is necessary to stop this infinite relaxation and it is derived from periodic sinusoidal energy of the crystal. When using the Peierls sinusoidal potential, a compact equilibrium core configuration corresponding to the Peierls analytical solution is obtained. The model is then extended to use generalized planar stacking fault energies as an input and is applied to the determination of properties of planar dislocation cores in crystalline materials. Dissociations of edge and screw dislocation cores in basal and prismatic planes of Zirconium are shown.
Theoretical Study of Local Electric Conductive Properties by Electronic Tension Density
Authors: Nozaki Hiroo , Senami Masato , Ichikawa Kazuhide , Tachibana Akitomo
Published: November 2016

We discuss the use of tension density for analyzing the electronic structure of a molecular system in a nonequilibrium steady state under the existence of electric current. By using the Rigged QED quantities defined at each point in space, such as tension density, local electric conductive properties are investigated. In particular, by computing benzenedithiol, it is numerically shown that the tension density serves as counter force to the Lorentz force density.
Scalable Methods to Obtain Superhydrophobicity onto Metallic Surface
Authors: Llorca-Isern Nuria , Escobar Romero Ana Maria , Rius Oriol
Published: November 2016

Superhydrophobic surfaces, with extremely high water contact angles (CAs) of more than 150° are of special interest due to their various anti-adhesive and self-cleaning properties. Recent studies demonstrate that the superhydrophobicity principally results from the presence of binary structures at both the micrometre and nanometre scales together with the low-energy wax-like materials on the surfaces. Materials with similar properties, to those of the lotus leaf structure are very useful in several areas, such as the aeronautical industry and civil engineering; so many methods have been developed to mimic the lotus leaf structure. Metals are very important and irreplaceable engineered materials in many industrial fields. An alternative method for enhancing superhydrophobicity on different metals is proposed. The method proceeds by coating the metallic surface with a superhydrophobic reactive such as dodecanoic acid being a common application its use in paints with eco-friendly properties. The goal of this study is to induce direct superhydrophobicity by a single step and coating process on prepared surfaces of pure commercial aluminium 99.9 wt %, pure commercial 99.9 wt % copper and stainless steel grade 316L (UNS S31603). The chemical reaction proceeds by etching the activated surface with lauric acid in ethanol solutions.