bluuebunny/crossref_metadata_2025 huggingface dataset:
Microemulsion mediated synthesis of nanocrystalline BaTiO3: possibilities, potential and perspectives
Authors: Pithan Christian , Schneller Theodor , Shiratori Yosuke , Majumder Subhasish Basu , Haegel Franz-Hubert , Dornseiffer Jürgen , Waser Rainer
Published: December 2013

The present study gives an overview on the potential, possibilities and perspectives that the synthesis of functional materials, such as BaTiO3, with microemulsions as the reaction medium offers. Well defined nanocrystalline particles in the form of powders for further ceramic processing, as well as stable colloidal dispersions for the preparation of coatings may be obtained. The paper describes the formation, phase behaviour and stabilization of microemulsions and related water/oil/surfactant systems that may be used as a nanoreactor during particle formation. The reaction principles of microemulsion mediated synthesis are outlined and some examples of structural aspects, revealing size effects in these systems are implemented using advanced characterization techniques, such as Raman spectroscopy. Finally, the preparation of mesoscopic layers, covering the thickness gap between thin film and thick film technology, is demonstrated.
The In–Pt–Sb phase diagram
Authors: Patrone Marta , Richter Klaus W. , Borzone Gabriella , Ipser Herbert
Published: December 2013

The ternary phase diagram In–Pt–Sb was studied in two isothermal sections at 400°C and 700°C, respectively, using X-ray powder diffraction (XRD), electron-probe microanalysis (EPMA), and metallographic techniques. The ternary phase reactions were determined by differential thermal analysis (DTA) in the composition range between 0 and 50at.% Pt. The obtained experimental phase diagram data were combined with literature data on the limiting binary systems to construct a ternary reaction scheme (Scheil diagram) in the investigated composition range between 0 and 50at.% Pt. The liquidus surface was derived from the results of DTA measurements.
Evolution of C-rich SiOC ceramics: Part II. Characterization by high lateral resolution techniques: electron energy-loss spectroscopy, high-resolution TEM and energy-filtered TEM
Authors: Gregori Giuliano , Kleebe Hans-Joachim , Blum Yigal D. , Babonneau Florence
Published: December 2013

In this Part II of the paper on the evolution of carbon-rich Si–O–C polymer-derived ceramics (PDCs), emphasis is placed on the strengths and limitations of transmission electron microscopy (TEM) techniques with high lateral resolution, i.e., electron energy-loss spectroscopy (EELS), high-resolution TEM (HRTEM) and energy-filtered TEM (EFTEM). Here, the identical SiOC materials, as described in Part I. EELS studies confirmed the progression of structural rearrangements within the SiOC matrix temperatures exceeding 1200°C. High-resolution TEM imaging showed that the SiOC matrices are indeed predominantly amorphous even upon high thermal treatment. Energy-filtered TEM analysis revealed, in contrast to the results obtained by Raman spectroscopy (Part I), that the excess free carbon phase undergoes a pronounced rearrangement within the amorphous microstructure. HRTEM characterization revealed the distribution of phases within the amorphous SiOC matrix; information that is not accessible by integral spectroscopic techniques. Discrepancies between the interpretation of experimental results obtained by local versus integral characterization tools are discussed in detail.
Nanostructured SiC/BN/C ceramics derived from mixtures of B3N3H6 and [HSi(Me)C≡C]n
Authors: Müller Anita , Gerstel Peter , Bunjes Natascha , Berger Frank , Sigle Wilfried , Müller Klaus , Weinmann Markus
Published: December 2013

Three borazine-modified polycarbosilanes were synthesized by reaction of poly[1,2-ethynediyl-(methylsilylene)], [HSi(Me)C≡C]n, and borazine, B3N3H6 using different stoichiometries. The polymeric precursors were transformed into inorganic Si–B–C–N materials by solid state thermolysis at 1400°C each in 88% yield. High temperature thermogravimetric analysis in an argon atmosphere showed no substantial decomposition reactions below 1800°C. Crystallization behavior up to 2000°C in a nitrogen atmosphere was studied by post-thermolysis heat treatment of as-obtained ceramics at various temperatures and subsequent examination of samples at room temperature using powder X-ray diffraction. Ceramics annealed at 1800°C were additionally characterized by transmission electron microscopy.
Effect of organic self-assembled monolayers on the deposition and adhesion of hydroxyapatite coatings on titanium
Authors: Zou Lijun , De Guire Mark , Wang Russell
Published: December 2013

Organic self-assembled monolayers with nitrogen-containing surface functionalities (amine or alkylammonium) were deposited on acid-etched titanium substrates. These were then coated with apatite deposited from 150% simulated body fluid at 37°C and pH = 7.6 for 2, 4, and 6days (after a 2-day “nucleation” step in contact with bioactive glass in 100% simulated body fluid). Scanning electron microscopy showed that precipitates were numerous on amine- and alkylammonium-modified titanium surfaces after nucleation for 2 days. X-ray diffraction at grazing incidence detected crystalline hydroxyapatite on the modified and unmodified substrates after growth for 2days. Tape peel tests followed by surface chemical analysis showed that the adhesion of the hydroxyapatite coating to the substrates was improved by amine and by alkylammonium modification of the etched titanium surfaces.
Interaction of functionalised surfaces on silica with dissolved metal cations in aqueous solutions
Authors: Majewski Peter
Published: December 2013

The study clearly shows that different metal cations were efficiently removed from water by employing coated silica particles with SO3H-terminated functionalized surfaces. Significant amounts of Fe, Mn, Ca, Mg, Na, and K could be removed from natural water samples with different concentrations varying from 0.075mg/l for Mn up to 12000mg/l for Na by stirring the functionalized silica particles in the water samples for 1h at room temperature. ICP–MS verify the removal of the elements and ToF-SIMS analyses clearly showed the presence of the elements on the particles after the treatment procedure. The removal of the metal cations is believed to be due to electrostatic attraction of the positively charged presumably hydrolysed metal cations to the negatively charged deprotonated SO3H-groups. However, from the current study it can not be excluded that chemisorption of the cations by the SO3H-group may be possible.
XRD and TEM study of NiO–LSGM reactivity
Authors: Rao Manga Venkateswara , Sturm Saso , Phillipp Fritz , Zinkevich Matvei
Published: December 2013

NiO–LSGM reactivity during sintering at high temperatures in air leads to the formation of LaNiO3-type phase which is found to be insulating for oxygen ions. XRD analysis of the NiO-LSGM samples after sintering at 1350°C in air showed cubic (Pm-3m) LaNiO3-based phase with a lattice parameter of 3.856Å in addition to the cubic structure of LSGM20-17. STEM/EDX analysis of the NiO–LSGM interface showed the presence of a Ni-containing perovskite phase (La, Sr)(Ga, Ni, Mg)O3−xin the diffusion layer of LSGM. The probable composition of the LaNiO3-type phase that formed during sintering is discussed.
Microstructure and dielectric properties of nanoscale oxide layers on sintered capacitor-grade niobium and V-doped niobium powder compacts
Authors: Störmer H. , Ivers-Tiffée E. , Schnitter C. , Gerthsen D.
Published: December 2013

Electrolytic anodization was used to form amorphous niobium oxide layers on niobium and V-doped niobium powder compacts which act as dielectric layers, e.g. in niobium-based solid electrolyte capacitors. The microstructure development within the layered structure niobium-niobium oxide was studied by scanning- and transmission electron microscopy in order to investigate the influence of processing parameters. It could be shown that the thickness as well as the quality of the oxide layers on niobium vary in a considerable range, depending on processing parameters. Examination of the influence of heat treatments on the structural properties of the oxide layers revealed remarkable changes at the niobium – niobium oxide interface upon heat impact exceeding 300°C. In contrast, the interface remains stable with respect to the as-anodized sample when annealing was performed at lower temperature.
Kinetic study of the + transformation reaction in a CuZnAl alloy
Authors: De Micco Georgina , Bohé Ana Ester , Pasquevich Daniel Miguel
Published: December 2013

In the present work we study the phase transformation reaction of a Cu-20Zn-7Al (wt.%) alloy by isothermal and non-isothermal in situ X-ray diffraction. An effective activation energy for each phase is obtained for the range between 275 and 395°C. The experimental data are also adjusted with the JMA equations. Finally, we present the TTT (time–temperature–transformation) diagram corresponding to the precipitation of alpha and gamma for the lower temperatures. Below 340°C, we found for this alloy that the gamma phase precedes the formation of alpha.
Thermodynamic properties of liquid Cu–In–Zn alloys
Authors: Knott Sabine , Chen C.-J. , Gehringer Friedrich , Mikula Adolf
Published: December 2013

The partial Gibbs energies of zinc in the liquid Cu–In–Zn system as a function of temperature and concentration were measured in the temperature range between the melting points of the alloys and 1073K using an EMF method with a liquid electrolyte. The thermodynamic properties were determined for 30 alloys at three different constant ratios of Cu:In of 1:2, 1:1, and 2:1 with zinc added in the concentration range between 5 and 90at.%. The integral Gibbs free energy and the integral enthalpy of mixing of the ternary system were calculated with the Gibbs Duhem equation.
Failure-mode dependence of the strengthening effect in Ti3AlC2/10 vol.% Al2O3composite
Authors: Chen Jixin , Liu Mingyue , Bao Yiwang , Zhou Yanchun
Published: December 2013

The high-temperature mechanical properties of both Ti3AlC2and Ti3AlC2/10vol.%Al2O3composite, including compressive strength, bending strength, and fracture behavior, were investigated. The strengthening effect caused by Al2O3strongly depended on the mode of failure: significant enhancement in strength was only observed under the brittle mode of failure; whereas under the ductile mode of failure the strengthening effect was impaired due to Ti3AlC2matrix softening and stress relaxation.
Effect of reinforcement size hybridizati on on the wear properties of SiCp/Cu Composites
Authors: Zhan Yongzhong , Xie Haofeng , Shi Xiaobo
Published: December 2013

Reinforcement size is an important factor that influences the mechanical and tribological properties of particulate reinforced metal matrix composites (PRMMCs). However, relatively few works have been carried out to investigate this issue. There are still many problems to be solved, on the optimum design of PRMMCs of tribological applications. In this work, copper-matrix composites reinforced with SiC particles of mono-size and hybrid-size are fabricated through a powder-metallurgy plus hot-extrusion method. The main purpose is to investigate the effect of reinforcement size hybridization on the dry sliding wear behavior of PRMMCs. The results indicate that finer particles result in a better reinforcing effect and significantly reduce the plastic flow and adhesive transfer of surface and subsurface material. The deeply embedded coarse particles bear the external applied load and resist the plowing effect of the counterpart. The different roles of the particulate components with various sizes promote the exertion of the other's strengthening function, therefore resulting in higher wear resistance.
Investigation of SiO2 thin films on Si substrates for use as standards for laser-acoustic measuring devices
Authors: Lucca D. A. , Herrmann K. , Klopfstein M. J. , Menelao F.
Published: December 2013

We report on an investigation of the suitability of SiO2 thin films for use as calibration standards for the measurement of elastic modulus by laser-acoustic measuring devices. Film thicknesses for a range of thin film standards, originally developed for the calibration of ellipsometers, were obtained by X-ray reflectometry, ellipsometry, and metrological scanning force microscopy. Using the calibrated values of film thickness, a laser-acoustic method was used to obtain the elastic moduli of the thin films. Nanoindentation of the films, performed at two different laboratories was used to provide an independent measure of the elastic modulus values. The modulus values determined by nanoindentation and the laser-acoustic method were found to agree within 4.6%, which was within the calculated uncertainty of the measurements performed. As a result of their high homogeneity with respect to film thickness and elastic modulus, their low surface roughness and the good laser-acoustic signal quality, the thin films investigated appear to hold promise as standards for laser-acoustic measuring devices.
Indentation behaviour of (011) thin films of III–V semiconductors: polarity effect differences between GaAs and InP
Authors: Largeau Ludovic , Patriarche Gilles , Bourhis Eric Le , Rivière Jean-Pierre
Published: December 2013

(011) thin films of GaAs and InP (220 and 250 mm thick, respectively) were deformed by a Vickers indenter at elevated temperatures (350–400°C) under loads in the range 0.4–2.9 N. For loads higher than 1.9N, symmetric punching through InP was detected at the opposite face while it was asymmetric through GaAs. In InP, when the punching mechanism took place, pile-up around the indent site progressively disappeared. Moreover, the measured plastic volumes reveal that plastic flow throughout the specimens is volume conservative, implying that pile-up and punching events are related. In GaAs, the anisotropic pile-up plasticity was studied using transmission electron microscopy. Models describing the material flow through the samples and reverse flow of matter are proposed.
Nanoindentation studies of stamp materials for nanoimprint lithography
Authors: Denkiewicz D. , Landis S. , Ratajczyk L. , Rymuza Z.
Published: December 2013

We tested the nanomechanical properties of various materials (Si, SiO2, Si3N4, AlCu, TiN) for the design of stamps used in nanoimprint lithography. Nanoindentation was used on both insulated and non-insulated areas. The test enabled an estimation of the nanohardness and Young's modulus of the tested materials (films). The results are very useful for selecting the material for a protective film on the stamps used in nanoinprinting lithography.
The absolute thermoelectric power of chromium, molybdenum, and tungsten
Authors: Brodowsky Horst , Chen Qiyuan , Xiao Zhongliang , Yin Zhoulan
Published: December 2013

In pure metals or homogeneous alloys, the number of electrons per atom as well as the pressure are constant in a temperature gradient, and the electrochemical potential of the electrons is a unique function of the temperature. That is why it is possible to obtain the thermopower of these materials not only in the conventional evaluation of the Onsager equations, which involves the calculation of two transport coefficients, but also with an alternative approach, which involves the calculation of the temperature dependence of the electrochemical potential. The method is illustrated with the calculation of the thermopower of Cr, Mo, and W from the density of states of these metals.
On the fatigue behavior of ultrafine-grained interstitial-free steel
Authors: Niendorf Thomas , Canadinc Demircan , Maier Hans Jürgen , Karaman Ibrahim , Sutter Steve G.
Published: December 2013

The present paper reports on the cyclic stress–strain response of body-centered cubic ultrafine-grained (UFG) interstitial-free (IF) steel severely plastically deformed at room temperature utilizing equal channel angular extrusion (ECAE). Low-cycle fatigue tests were conducted with various strain amplitudes and strain rates on samples obtained through different ECAE routes and number of ECAE passes in order to determine the optimum processing route(s) for improved fatigue response of this material. UFG IF steel is superior to its coarse grained counterpart under both monotonic and cyclic loading in terms of properties, such as stress ranges tolerated, strength levels attained, and the corresponding fatigue behavior. All UFG steels subjected to more than 4 ECAE passes exhibit stable cyclic stress–strain response. Moreover, it was shown that dynamic grain coarsening, which usually leads to cyclic softening in UFG materials, is not prevalent in the ECAE processed UFG IF steel. For representing the fatigue life of UFG IF steel, the parameter after Smith, Watson and Topper, which is an indication of energy dissipation per cycle, proved adequate while comparing materials obtained through different ECAE routes.
Possibilities and limits in thermohydrogen processing of beta titanium alloy Timetal®10-2-3
Authors: Christ Hans-Jürgen , Lohse Georg
Published: December 2013

The microstructure of the metastable -titanium alloy Timetal®10-2-3 was changed systematically by means of thermohydrogen processing, in order to improve the mechanical properties. The thermodynamic and kinetic data-base was determined experimentally and the change in the beta transus temperature was determined quantitatively. The results were used to design a 4-step heat treatment process involving hydrogen during the first two steps. A comparison of the fatigue properties of the standard heat-treated and the thermohydrogen-processed alloy revealed that, despite the increase of the monotonic strength of the thermohydrogen-treated alloy, the fatigue limit is slightly reduced, while the fatigue crack growth threshold remains almost unaffected. From this correlation a strategy can be deduced for a further improvement of the thermohydrogen-processing procedure, in order to tailor the fatigue properties according to the requirements of the respective application.
Mechanical properties and microstructural changes of ultrafine-grained AA6063T6 during high-cycle fatigue
Authors: Hockauf Matthias , Meyer Lothar W. , Halle Thorsten , Kuprin Corinna , Hietschold Michael , Schulze Steffen , Krüger Lutz
Published: December 2013

Fatigue behaviour and mechanical properties of peak-aged AA6063T6 with ultra-fine grain size, produced by equal channel angular extrusion, were evaluated with special emphasis on the microstructure before and after cyclic loading. The strength significantly increased with grain size reduction and is described by an exponential power-law constitutive relationship. A remarkable enhancement of fatigue life compared to commercial AA6063T6 with coarse grains was found in the high-cycle regime after the first two extrusions. Further extrusions eliminated this improvement. It is shown that the optimum fatigue performance correlates very well with the minimum tensile ductility. Electron backscatter diffraction revealed that the material behaviour can basically be attributed to the grain boundary characteristics. Low grain boundary misorientation angles yield the best fatigue performance in the ultrafine-grained microstructure.
Analysis of failure behaviour of carbon/carbon composite made by chemical vapour infiltration considering fibre, matrix and interface properties
Authors: Ermel Ralf , Beck Tilmann , Kerscher Eberhard
Published: December 2013

The mechanical properties of a unidirectional carbon/carbon (C/C) composite with a mainly highly textured matrix are investigated in tensile tests for the as-received state and after heat treatment from 1600°C to 2500°C. In order to interpret the composite behaviour single fibre tests, analyses of fracture surfaces and tests on infiltrated fibre felts were conducted. The fibre–matrix shear strength was determined by push-out indentation tests. Strength and ductility only change slightly although the strength of the fibres decreases significantly with increasing heat treatment temperature (HTT). The reason is a reduced bonding strength between fibre and matrix with increasing HTT. The Young's modulus of C/C composites increases with HTT. The best mechanical properties of the composite are reached by finding a compromise between sufficient fibre strength and weakened fibre-matrix strength at a HTT of 1600°C.
Grinding-induced microstructural gradients and residual stresses in the surface layers of carbon steel and pure tungsten
Authors: Okolo Brando , Wanner Alexander
Published: December 2013

Flat samples of AISI 1080 carbon steel and commercially pure tungsten were surface-treated using a reciprocating table-type grinding machine. Cross sections of the subsurface microstructure induced by this mechanical finishing process were prepared and imaged by focussed ion beam methods. Depth profiles of the residual normal and shear stresses were analysed using synchrotron X-ray diffraction and correlated to the observed microstructural gradients. The stress partitioning between the hard cementite and the soft ferrite phases in the ground steel samples is discussed in detail.
Damage tolerance: fracture mechanics in design
Authors: Schwalbe Karl-Heinz , Zerbst Uwe
Published: December 2013

Fracture mechanics methods are usually applied if a crack-like flaw is detected in a structural component and a decision has to be taken with respect to limited further service, or if a failure case has to be assessed. The present contribution demonstrates various options for the inclusion of fracture mechanics in the design process. A number of fracture mechanics based concepts are available; these include classical damage tolerance, proof testing, and periodic removal of cracks through grinding. Until now, less attention has been paid to application in the design stage, where, however, consistent inclusion of fracture mechanics in design promises substantial potential in designing against failure.
Polymer-derived Si–C–N ceramics reinforced by single-wall carbon nanotubes
Authors: Burghard Zaklina , Schön Davina , Garstel Peter , Bill Joachim , Aldinger Fritz
Published: December 2013

Nanocomposites made of polymer-derived Si–C–N ceramic reinforced by single-wall carbon nanotubes (SWCNTs) were prepared for the first time. The synthesis procedure involved ultrasonic dispersion of the nanotubes into a liquid polysilazane precursor polymer, followed by cross-linking and thermolysis. With the aid of nanoindentation testing, dependence of the mechanical properties of the composites on the concentration and agglomeration state of SWCNTs, was studied. The nanotube-filled composites showed improved mechanical performance, as reflected by an increase in Young's modulus which was found to be correlated with the microstructure of the composites, in particular the degree of dispersion of the nanotubes inside the matrix, whereas the hardness is hardly affected.
Effect of surface roughening on increasingthe spectral selectivity of cermet solarselective absorbers
Authors: Nejati M. Reza , Clasen Rolf
Published: December 2013

The spectral selectivity of Cu–Al2O3 cermet solar absorbers was studied theoretically and experimentally in different layer designs. The results showed clearly that, by increasing the substrate temperature during film deposition, the desired random roughness features will be created on the surface of the cermet, which leads to higher selectivity. Theoretical simulation showed that a single cermet structure with the assistance of an anti-reflection layer, results in the best optical properties. Instead of such a structure, which is sensitive to fine thickness control, it was tried experimentally to increase the selectivity of a single cermet structure as much as possible using a roughness template layer. Surface roughening using such a layer design increased the solar absorptance from 0.840 to 0.956 while keeping the thermal emittance almost unchanged at about 0.028.
Progress in understanding the metallurgy of 18% nickel maraging steels
Authors: Rao Muktinutalapati Nageswara
Published: December 2013

Maraging steels based on iron–nickel martensite constitute a very important family of high-strength steels, which distinguishes itself by demonstrating an unparalleled combination of excellent fabricability and high strength and fracture toughness after heat treatment. Heat treatment of these steels has now been perfected to ensure consistently high levels of strength, ductility, and toughness in a variety of product shapes and sizes. Cobalt-free variants have been commercialized as part of efforts to save production costs. Further knowledge has been generated on 18% nickel maraging steels regarding phases precipitating during aging, thermal embrittlement, thermal cycling and austenite reversion/retention and their effect on mechanical properties. The paper reviews the progress made over the last one and half decades.
Experimental study and thermodynamic assessment of the ZrO2–DyO1.5 system
Authors: Wang Chong , Zinkevich Matsvei , Aldinger Fritz
Published: December 2013

The phase equilibria and thermodynamic properties in the ZrO2 – DyO1.5 system have been studied using the experimental methods of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, differential thermal analysis and high temperature drop calorimetry. The tetragonal + fluorite and fluorite + C-Dy2O3 phase equilibria between 1400 °C and 1700 °C have been determined, together with the enthalpy increments of the materials with 30 mol.% and 50 mol.% DyO1.5 in the temperature range 200 – 1400 °C. Furthermore, the martensitic transformation temperatures (As, Ms) have been measured for the samples with 1 and 2 mol.% DyO1.5. Finally, thermodynamic assessment has been carried out using the experimental results obtained and literature data.
Thermal stability of ECAP processed pure Cu and CuZr
Authors: Molodova X. , Khorashadizadeh A. , Gottstein G. , Winning M. , Hellmig R. J.
Published: December 2013

Samples of pure Cu and Cu with 0.17 wt.% Zr were processed by equal-channel angular pressing up to 12 passes with a 90° die angle using route Bc. Microstructure evolution after deformation and subsequent heat treatment of this severely deformed material was investigated. The deformed and annealed states were characterized by electron back scatter diffraction, transmission electron microscopy, optical microscopy and microhardness tests. The microstructural changes were compared to the behavior of specimens produced by conventional cold rolling. The annealing phenomena were analyzed with regard to recrystallization and grain growth mechanisms. It is shown that the microstructural change during annealing of equal-channel angular pressing deformed specimens has to be associated with discontinuous recrystallization. CuZr samples showed a significantly higher thermal stability against recrystallization than pure Cu samples. This is demonstrated to be primarily due to impurity drag.
Enhancement in mechanical behavior and wear resistance of severe plastically deformed two-phase Zn–Al alloys
Authors: Purcek Gencaga , Karaman Ibrahim , Yapici Guney Guven , Al-Maharbi Majid , Kuçukomeroglu Tevfik , Saray Onur
Published: December 2013

The microstructural evolution, tensile response and wear properties of a two-phase Zn – Al alloy (Zn-8 wt.% Al, ZA-8) have been studied after severe plastic deformation by equal channel angular extrusion (ECAE). The experimental results reveal that the strength levels of the ECAE processed samples were considerably improved regardless of the processing route. More importantly, the elongation at fracture was dramatically increased after ECAE. The optimum tensile properties (high strength and high ductility) were reached after eight ECAE passes following route BA. It was also found that the wear rate of severe plastically deformed ZA-8 is considerably lower than that of the as-cast alloy, especially under high applied pressures, demonstrating improved wear resistance of ZA-8. Moderate strength and high ductility along with improved wear resistance in the ECAE processed ZA-8 samples in comparison with the brittle as-cast alloy makes these alloys attractive for wear-sensitive structural applications.
Microscale characterization of bitumen – back-analysis of viscoelastic properties by means of nanoindentation
Authors: Jäger Andreas , Lackner Roman , Stangl Klaus
Published: December 2013

In order to understand the complex thermo-rheological behavior of asphalt, stemming from the viscoelastic nature of bitumen, the nanoindentation (NI) technique is employed. Hereby, the load history applied onto the indenter tip is characterized by a loading, holding, and unloading phase. As regards the identification of viscoelastic properties, a recently published back-analysis scheme, employing the holding phase of the NI test, is extended towards fractional-creep models. In fact, this type of model is found to perfectly describe the viscoelastic behavior of bitumen. Based on the identified viscoelastic model parameters, the influence of loading rate, maximum load, and temperature on these parameters is investigated. Hereby, the temperature dependence of creep parameters follows an Arrhenius-type law. In addition to the model parameters, application of the so-called grid-indentation technique within NI testing provides insight into the bitumen microstructure and the mechanical behavior of the different bitumen phases. The results obtained indicate the existence of a string-like microstructure embedded into a less viscous matrix material.
Bestimmung der Messunsicherheit bei der Härteprüfung, Einbringung der Bestimmung der Messunsicherheit in das QMH, Verfahrensanweisung des Qualitätsmanagements
Authors: Baudzus Dietmar , Polzin Thomas , Schwenk Dieter
Published: December 2013

Kurzfassung

Nach der nächsten Revision der Normen für die Härteprüfung [1–3] wird eine Bestimmung der Messunsicherheit [4,5] Teil der Normen sein. Die Autoren wollen die Anwender von Härteprüfmaschinen [6–13] darauf aufmerksam machen, wie die Messunsicherheit in die Teile 1 der Normen [1–3] als informative Anhänge eingebracht werden. Die Veröffentlichung besteht aus drei Abschnitten. In der ersten Veröffentlichung [14] werden insbesondere die beiden vorgeschlagenen Methoden für Teil 1 der ISO Normen für Härteprüfung erklärt. In Abschnitt 2 [15] wird ein EXCEL-File beschrieben für die periodische Prüfung und die Bestimmung der Messunsicherheit. Der folgende Teil drei betrifft die Einbringung der Bestimmung der Messunsicherheit in das QMH.
Gemeinschaftsversuch an einem Sandwichverbund
Authors: Carle Veronika , Täffner Ulrike , Kopp Wolf-Ulrich
Published: December 2013

Kurzfassung

Der Arbeitskreis Probenpräparation im Fachausschuß Materialographie der DGM führte im Jahr 2003 als Gemeinschaftsversuch die metallographische Anschliffpräparation an einem Sandwich-Werkstoffverbund durch.

In 15 metallographischen Laboratorien wurde das Probenmaterial, bestehend aus Stahl-Aluminiumschaum-Stahl mit den zur Verfügung stehenden Geräten und Verbrauchsmaterialien präpariert, das Gefüge kontrastiert und qualitativ und quantitativ beurteilt.

Die unterschiedlichen Präparationsabläufe werden beschrieben, die dokumentierten Gefüge gezeigt und die unterschiedlichen Kommentare der Teilnehmer zusammengefasst und ausgewertet.

Hinweise zur optimalen Präparation werden gegeben.
Effects of Al Sputtering Power on the Structure and Growth Morphology of (Ti, Al)N/AlN Multilayer Coatings
Authors: Üstel Fatih
Published: December 2013

Multilayer TiAlN and AlN coatings were deposited from two targets onto high speed steel (HSS) and hard metal (HM) substrates by pulsed DC magnetron sputtering. TiAl target power was held constant while aluminum target power was varied. Scanning electron microscopy and X-ray diffraction techniques were used for the structural and morphological characterization. Aluminum target power had an influence on the coating structure and morphology. Coatings produced with low aluminum target power had B1 type cubic structure. As the power was increased, the hexagonal structure becomes clearer.
Correlation Between the Microstructure of Galvannealed Coatings and the Defoliation during Press Forming
Authors: Hong Moon-Hi
Published: December 2013

The defoliation properties of galvannealed coating, so-called powdering and flaking, in continuous galvanizing line were investigated by scanning electron microscopy, X-ray diffraction, roughness profiler and deep drawing test. Both aluminum content in molten zinc and galvannealing temperature were turned out to be critical factors on the microstructure and mechanical properties of galvannealed coatings. Below 0.135 wt% Al, coating surface composed of the mixture of granular d1p and columnar z phases. While, above 0.155 wt% Al, coating surface contained the mixture of granular d1p and pan-cake d1k phases. The appearance of brittle d1k phase approximately 10 μm in size can account for the high amount of defoliation during deep drawing test. The formation of relatively ductile z phase and thin G phase contributes to improve the press formability. The optimazation of the surface microstructure controlling the ratio of granular d1p and columnar z phases was important to reduce the powdering.
Einfluss der Lotzusammensetzung auf die Gefügeentwicklung in Magnesium-Lötverbindungen
Authors: Wielage Bernhard , Mücklich Silke
Published: December 2013

Kurzfassung

Ein in der jüngsten Vergangenheit stetig gestiegener Einsatz von Magnesiumbauteilen wirft die Frage nach geeigneten Fügetechnologien auf. Es wird ein umweltfreundliches Lötverfahren entwickelt, welches durch Ultraschall auf den Einsatz von Flussmitteln verzichtet und gleichzeitig gut in den Produktionsprozess integrierbar ist. An den Magnesiumgrundwerkstoffen AZ31 und AZ91 werden Lötversuche durchgeführt. Als Lote dienen eutektikumsnahe Legierungen auf der Basis Mg-Zn bzw. Mg-Zn-Al.

In Abhängigkeit von der Zusammensetzung der Lotlegierung werden unterschiedliche Gefügeausbildungen beobachtet: Steigende Aluminiumgehalte zwischen 0 und 10 Gew.-% bewirken eine zunehmende Vergröberung der eutektischen Gefüge im Nahtbereich.
Materialmikroskopie unter besonderer Berücksichtigung der Kunststoffe
Authors: Trempler Jörg
Published: December 2013

Kurzfassung

Messende lichtmikroskopische Methoden, wie z.B. die Bestimmung der optischen Doppelbrechung haben überall dort eine überragende Bedeutung, wo in den zu untersuchenden Materialien bedingt durch den molekularen Aufbau mit lichtmikroskopischen Methoden kein Gefüge sichtbar gemacht werden kann. Das trifft auf alle amorphen Kunststoffe, wie z. B. Polystyrol zu.

Ein besonderer Vorteil der Bestimmung optischer Daten an Kunststoffen besteht in der engen Korrelation dieser Daten zu den Kunststoffeigenschaften. Dadurch lassen sich relativ einfach online Einrichtungen zur zerstörungsfreien Charakterisierung der Produkte im Fertigungsprozess integrieren.

Aber auch an teilkristallinen Polymeren können messende Verfahren zusätzlich zu der dort oft möglichen Gefügebewertung eingesetzt werden und liefern zusätzlich wertvolle Informationen. Diese Methoden werden im Teil B des Artikels ausführlich dargestellt.

Neben der Bestimmung optischer Daten können zu den messenden Verfahren der Lichtmikroskopie noch eine Reihe weiterer Messmethoden gerechnet werden. Dazu gehören z. B. die Bestimmung der Mikrohärte, die Tief- und Hochtemperaturmikroskopie, Kristallisations-, Auflösungs-, Quell- und Diffusionserscheinungen im Mikroskop in Mikroküvetten sowie DTA – Untersuchungen an geringsten Mengen teilkristalliner Kunststoffe und an Kunststoffgemischen sowie-blends in speziellen Mikroheiztischen. Diese Verfahren werden ebenfalls im Teil B beschrieben.
Silicon Carbide from Sludged Silicon Powder
Authors: Choi Mi-Ryoung , Kim Yeong-Cheol , Chang Young-Chul
Published: December 2013

Sawing silicon ingot with abrasive slurry generates sludge that includes abrasive powders, cutting oil, and silicon powders. The abrasive powders and cutting oil are being separated and reused. Mixing the remained sludged silicon powders with carbon powders and subsequent heattreatment are conducted to produce silicon carbide. Thermodynamic calculation is performed to find an optimum formation condition for the silicon carbide. Silicon carbide whiskers are mainly formed at 1400°C in a closed system, instead of silicon carbide powders. Impurity related mechanism is attributed to the formation of the silicon carbide whiskers, as metal impurities are contained in the sludged silicon powders.
Bildanalytische Formanalyse und Klassifizierung der irregulären Graphitmorphologie in Gusseisen
Authors: Velichko A. , Mücklich F.
Published: December 2013

Kurzfassung

Die Unterscheidung der verschiedenen Graphitmorphologien in Gusseisen erfolgte bisher im Wesentlichen qualitativ durch subjektiven Vergleich mit Richtreihenbildern. In Hochleistungsanwendungen im Motorenbau werden nunmehr objektive quantitative Messungen der jeweiligen Graphitanteile benötigt, damit die mechanischen Eigenschaften reproduzierbar erreicht werden können.

Vorgestellt werden bildanalytische Untersuchungen zur automatischen Klassifizierung von Lamellen-, Vermikular- und Kugelgraphitformen, sowie Graphitformen in Temperguss. Dabei wurden insbesondere teilchenbasierte Messmethoden angewendet. Unterschiedliche Formparameter wurden in dieser Arbeit zusammengefasst, und ihre Relevanz für die Charakterisierung und Klassifizierung irregulärer, komplexer Graphitteilchen in Gusseisen wurde bestimmt. Es zeigte sich, dass die Kombination der Formparameter Rundheit und Kompaktheit die präziseste Klassifizierung liefert. Ein Klassifizierungsalgorithmus wurde mit Berücksichtigung der Abhängigkeit der Formparameter von der Teilchengröße entwickelt. Die traditionelle subjektive Analyse der Gusseisengefüge anhand EN ISO 945 kann durch die Anwendung der neu vorgeschlagenen Methode mit einer automatischen reproduzierbaren Graphitformcharakterisierung und Klassifizierung deutlich verbessert werden.
Rapidly Solidified Microstructure and Failure Analysis of Powder Metallurgy Al-Si Alloys
Authors: Hong Soon-Jik , Kim Ha-Young , Kim Gyeong-Hwan
Published: December 2013

The microstructure of the extruded bars showed a homogeneous distribution of eutectic Si and primary Si particles embedded in the Al matrix. The grain size of α-Al varied from 150 to 600 nm and the size of the eutectic Si and primary Si in the extruded bars was about 100–200 nm. The room temperature tensile strength of the alloy with a powder size < 26 μm was 322 MPa, while for the coarser powder (45–106 μm) it was 230 MPa. With decreasing powder size from 45–106 μm to < 26 μm, the specific wear of all the alloys decreased significantly at all sliding speeds due to the higher strength achieved by ultra-fine grained constituent phases. The thickness of the deformed layer of the alloy from the coarse powder (10 μm at 3.5 m/s) was larger on the worn surface in comparison to the bars from the fine powders (5 μm at 3.5 m/s) due to the lower strength of the bars with coarse powders. The fracture mechanism of failure in tension testing and wear testing was also studied.
Metallographische Untersuchung eines Toledostahlschwertes
Authors: Salinas Ruiz Ma Dolores , Criado Martin A. Javier , Valverde Virginia Ramos , Peces Raquel Arévalo , Fernández Jorge Chamón , Dietz Christian , Martínez Juan A. , Criado Portal Antonio J.
Published: December 2013

Kurzfassung

In der vorliegenden Arbeit wurde die metallographische Struktur eines Paradeschwertes untersucht, welches in der Königlichen Fabrik zu Toledo, Spanien, um das Jahr 1851 hergestellt wurde. Das Schwert war Teil der Uniform eines Kavallerieoffiziers. Zur Untersuchung wurden Rasterelektronenmikroskopie (REM) sowie energiedispersive Röntgenstrahlanalyse (EDX) verwendet. Es konnte die hervorragende Verarbeitung des Schwertes, bestehend aus zwei durch Heißschmieden verschweißten Stählen unterschiedlichen Kohlenstoffgehaltes, aufgezeigt werden. Dies erklärt auch die ausgezeichneten mechanischen Eigenschaften des Schwertes, sowie den historisch herausragenden Ruf von Hieb- und Stichwaffen aus der Königlichen Fabrik zu Toledo.
TEM Study of Bainitic Low-Carbon HSLA Steel: The Orientation Relationships of Cementite
Authors: Illescas Silvia , Fernández Javier , Asensio Juan , Guilemany Josep Maria
Published: December 2013

Two different bainitic structures can be present in steel depending on the heat treatment to which the samples are subjected. The two different types of bainitic structures exhibit a different orientation relationship between the cementite and the ferrite matrix. The Pitsch orientation relationship is observed in upper bainite while the Bagaryatski orientation relationship is observed in lower bainite [1]. Different heat treatment samples of low-carbon High Strength Low Alloy (HSLA) steel were studied using TEM observations in order to ascertain the orientation relationship between ferrite and carbide in the different bainitic structures and to determine whether this relationship may indicate the type of bainitic structure.
Herstellung lamellarer Gefügetypen in intermetallischen TiAl- Legierungen und deren Charakterisierung
Authors: Schnitzer Ronald , Chladil Harald F. , Scheu Christina , Clemens Helmut , Bystrzanowski Slawomir , Bartels Arno , Kremmer Sascha
Published: December 2013

Kurzfassung

Im Rahmen dieser Arbeit wurden zwei lamellare Gefügetypen in γ-TiAl-Basislegierungen untersucht. Zum einen erfolgte die Herstellung der voll lamellaren Gefüge mittels einer Glühung im α-Einphasengebiet und anschließend langsamer Abkühlung. Das resultierende Gefüge besteht aus lamellaren γ-TiAl/α2-Ti3Al-Kolonien, wobei diese die ehemaligen α-Körner darstellen. Innerhalb einer Kolonie sind die γ/α2-Lamellen parallel angeordnet und weisen eine bestimmte kristallographische Orientierungsbeziehung auf. Zum anderen konnte mit Hilfe der Massivtransformation und anschließender Auslagerungsglühung eine neuartige lamellare Mikrostruktur eingestellt werden, die auf konventionellem Weg nicht realisierbar ist. Dabei scheiden sich aus dem massiv transformierten γm feine α2-Ti3Al-Lamellen aus, die in einem Winkel von 70,5° zueinander orientiert sind. Neben einer ausführlichen Beschreibung der Mikrostruktur werden die Orientierungsbeziehungen beider lamellarer Gefügetypen während der Entstehung beschrieben und die Keimbildung der γ-Lamellen in α-Körnern mittels Transmissionselektronenmikroskopie (TEM) untersucht.
Material Analysis of the Late 19th Century Iron Based Heritage Listed Constructions
Authors: Audy Jaromir , Audy Katarina
Published: December 2013

The use of iron based materials in building of highly decorated pavilions, rotundas and large constructions reached its zenith in the second half of the 19th century. Over the following century, due to atmospheric corrosion, many of these historical objects disintegrated so badly that they needed urgent attention from conservation. The present study was set up to examine the metallurgical features of two famous buildings — the Palm House in the Botanic Garden in Adelaide, South Australia (S. A.) and the Band Rotunda in Kosice City in Slovakia, allowing some rules for reconstruction to be laid down. In both cases, the ‘iron based’ construction material and ornaments investigated were made in Germany at the end of the 19th century.
The Production of Ultra Fine Grained Al-SiCp Composites Produced via High Energy Ball Milling
Authors: Özdemir Ismail , Ahrens Sascha , Mücklich Silke , Wielage Bernhard
Published: December 2013

Aluminum-copper alloy EN AW 2017 (Al-3.9Cu-0.6% Mn-0.7%Mg) based composite powders reinforced with 5 and 15 vol. % SiC particulates were produced by high energy ball milling (HEM) process. The milling times range between 10 min and 6 h. After milling for a certain time, i.e., 2 h, the cellular structure of CuAl2 intermetallic particles initially present in the matrix and precipitate at the grain boundaries that were destroyed and distributed along the deformation axis. XRD results clearly showed that the X-ray diffraction peaks of CuAl2 disappear after 2 h milling time suggesting that the submicrometer sized intermetallic CuAl2 particles dissolved into the aluminum matrix. This was also confirmed by SEM investigation. During subsequent milling of composite blends (2 h and more) the reinforcement particles were heavily fragmented. Thus they exhibited a significant reduction in size. The results indicate that the particle size of SiC and CuAl2 was refined greatly after 6 h of high energy ball milling. However, it is clear that the particle size distribution even after the longest period of milling, 6 h, showed no significant narrowing. The crystallite size of the composites was reduced to below 45 nm which was confirmed by X-ray line broadening analysis.
Einfluss von Aluminiumnitrid auf die Hochtemperaturduktilität von stranggegossenen Brammen
Authors: Winkelhofer Florian , Parteder Erik , Clemens Helmut , Leitner Harald , Spiradek-Hahn Krystyna , Kozeschnik Ernst
Published: December 2013

Kurzfassung

Während des Stranggießprozesses treten in der erstarrten Strangschale der Brammen thermisch und mechanisch induzierte Spannungen und Dehnungen auf, die bei ungünstiger Prozessführung gepaart mit dem spezifischen Werkstoffverhalten zu Rissen führen können. Eine wichtige Phase im Prozessablauf ist die γ-α-Umwandlung, welche die Duktilität des Werkstoffes stark verringert und die Rissgefahr erhöht. Zusätzlich sollten sich laut Literatur feine Aluminiumnitridausscheidungen negativ auf Hochtemperatureigenschaften der Stähle auswirken. Ziel der Arbeit ist es, die möglichen Auswirkungen von Aluminiumnitrid-Ausscheidungen für Baustähle im Legierungsbereich um 0,2 Masse-% Kohlenstoff anhand von Heißzugversuchen zu untersuchen.

Die Ergebnisse der Heißzugversuche in Verbindung mit den mikrostrukturellen Untersuchungen ergaben jedoch, dass unterschiedliche Abkühlbedingungen keinen signifikanten Einfluss auf die Hochtemperaturduktilität haben.
Experimentelle Untersuchungen über Schneid- und Verschleißcharakteristiken der TiCN-CrN-beschichteten C 80-Stähle
Authors: Cakan Ahmet , Özkaner Vedat , Yildirim M. Mustafa
Published: December 2013

Kurzfassung

Harte Plattierschichten aus Titanium Karbonitriden (TiCN) und Chromnitriden (CrN) werden heute in der Metallbearbeitung und Werkzeugindustrie, vor allem zum Schutz der Span abhebenden Schneidwerkzeuge gegen Verschleiß- und Korrosionswirkungen, genutzt. In dieser Arbeit wurden die Oberflächen der Schneidspitze der aus unlegiertem C 80-Stahl hergestellten Scheidwerkzeuge mit einer Lichtbogen-Dampfabscheidungstechnik (CAVD) mit dünnen TiCN- und CrN-Schichten kathodisch überzogen. Die Schneidcharakteristiken und Verschleißverhalten der erhaltenen Schneidwerkzeuge wurden an einer konventionellen Drehbank experimentell untersucht. Die Veränderung der chemischen Zusammensetzung und die Eigenschaften der mit Nitrid-Schichten plattierten Oberflächen wurden mit SEM-Aufnahmen, mit einer so genannten “line scan“-Analyse und mit röntgenographischen Diffraktogrammen (XRD) bestimmt. Schneidfähigkeitsprüfung und Verschleißverhalten der erzeugten Werkzeuge, deren Schneidspitze mit sehr dünnen TiCN- und CrN-Schichten überzogen wurden, wurden mit einem im Monitor direkt verfolgbaren System (on-line monitoring System) ermittelt. Die Ergebnisse zeigten unter anderem, dass die TiCN-plattierten Scheidwerkzeuge mehr Verschleißwiderstand aufwiesen, als diejenigen, die mit CrN-Schichten überzogen wurden.