bluuebunny/crossref_metadata_2025 huggingface dataset:
Heißrissbildung in der Wärmeeinflusszone lasergebohrter Turbinenschaufeln aus der Nickelbasis-Superlegierung René 80
Authors: Matijasevic-Lux Biljana , Neidel Andreas , Riesenbeck Susanne , Ullrich Thomas , Völker Jörg , Wallich Sebastian
Published: December 2013

Kurzfassung

Moderne Filmkühltechnologien für Heißgasteile von Gasturbinen mit nach wie vor steigenden Eintrittstemperaturen erfordern spezialisierte Fertigungsverfahren. Inzwischen ist der Laser das bevorzugte Werkzeug zum Herstellen einer großen Anzahl kleiner Filmkühlbohrungen in Turbinenteilen aus Nickelbasis-Superlegierungen. Die meisten dieser Werkstoffe sind allerdings in der an die umgeschmolzene Schicht grenzenden Wärmeeinflusszone heißrissempfindlich. Umfangreiche metallographische Untersuchungen, die zur Parameteroptimierung durchgeführt wurden, zeigten für den Werkstoff René 80 einen ausgeprägten Gefügeeinfluss auf die Heißrissempfindlichkeit, d.h. gleiche Laserparameter können je nach lokaler Gefügeausbildung in unmittelbarer Bohrungsumgebung zu unterschiedlichen Heißrisslängen führen. Korngröße, Korngrenzenform und -lage sowie die Ausbildung der Primärcarbide scheinen eine wesentliche Rolle zu spielen. Diese Zusammenhänge sollten bei der Festlegung zulässiger Heißrisslängen berücksichtigt werden, da eine Einflussnahme auf die lokalen Gefügeparameter bei konventionellen Feingussprozessen mit wirtschaftlich vertretbarem Aufwand nicht realistisch erscheint.
Modification and Characterization of Metallized Tips for Scanning Probe Microscopy
Authors: Ritz Yvonne , Masalska Agata , Hecker Michael , Gotszalk Teodor , Zschech Ehrenfried
Published: December 2013

The characterization of nanoscale regions in present and future device structures of leading-edge microelectronic products requires probes with dedicated features tailored on the nanoscale. SPM tips are used not only for conventional AFM characterization, but also for electrical, thermal and optical investigation of devices. For particular applications as nano-Raman spectroscopy or conductive AFM, highly reproducible metal tips or metallized tips are needed. In this paper, new approaches to tailor those tips using the FIB technique, and to characterize the tips using dedicated structures and adapted AFM methods are described. Based on a numerical procedure, the tip quality is described quantitatively. The described preparation and calibration techniques offer new possibilities for the routine application of nanostructures and nanodevices as needed for advanced SPM techniques and nanosensors.
Metallographie luftexponierter Aluminium-Kohlenstofffaser-Verbundwerkstoffe mit Grenzflächenkarbiden
Authors: Schiffl Andreas , Schulz Peter , Kainhofer Christa
Published: December 2013

Kurzfassung

Kohlenstofffaser-Aluminiummatrix-Verbundwerkstoffe sind attraktive Kandidaten für Bauteile, die einen kleinen thermischen Ausdehnungskoeffizienten bei gleichzeitig hoher Wärmeleitfähigkeit aufweisen müssen. Die Herstellung von Aluminium-Kohlenstoff-Verbund-werkstoffen erfolgt durch Gasdruckinfiltration in einem Autoklav. Die wichtigsten Herstellungsparameter sind die Schmelzetemperatur und die Zeit, in der die Fasern mit der Aluminiumschmelze in Berührung stehen. Wenn eine Reaktion von flüssigem Aluminium mit den Kohlefasern auftritt, können Aluminiumkarbide gebildet werden, diese schwächen den Verbund enorm.

Die Schwierigkeit in der Präparation dieser kleinen Karbide liegt darin, dass diese wasserlöslich sind und nur im Faser/Matrix-Interfacebereich zu finden sind. Es muss daher besonders auf Wasserfreiheit geachtet werden.

Die Metallographie ist ein entscheidender Baustein zur Beurteilung der Qualität von Kohlenstofffaser verstärkten Aluminiummatrix-Verbundwerkstoffen. Sie ist leicht anzuwenden und lässt Rückschlüsse auf die Verbundeigenschaften zu. Mit Hilfe der Metallographie lassen sich Herstellungsparameter eingrenzen und geeignete Fasersorten selektieren.
The Effect of Welding Parameters on the Microstructure and Mechanical Properties of Friction Stir Welded AA 7075
Authors: Yeni Çinar
Published: December 2013

In this study, aluminum alloy 7075 (AA 7075) has been friction stir welded by using three different rotation speeds and two different welding speeds. The aim is to determine the optimum welding parameters concerning these two variables for AA 7075. Microstructural examination, hardness measurements and room temperature tensile tests have been carried out in order to determine the optimum combination. The results show that higher rotation speeds have yielded higher mechanical properties. Some porosity has been obtained for the lowest rotation speed.
Thermisches Ätzen zur Bestimmung der Austenitkorngröße in kohlenstoffarmen Stählen
Authors: Pöhl Christopher , Gamsjäger Ernst , Leitner Harald , Clemens Helmut
Published: December 2013

Kurzfassung

In der einschlägigen Literatur findet man Arbeiten, welche die Bestimmung der Austenitkorngröße nach der Methode des thermischen Ätzens beschreiben. Diese Methode wurde weiterentwickelt. Zum thermischen Ätzen wurde die Heizvorrichtung eines Bähr 805 A/D Abschreck- und Umformdilatometers mit Vakuumkammer verwendet. An den beiden Enden der Probe wurden Molybdän-Plättchen als Gettermaterial mit Hilfe eines organischen Klebstoffs befestigt. Anschließend wurde die Probe der Austenitisierungsbehandlung unterzogen. Die Verbrennung des organischen Klebstoffs in der Probenkammer senkte den vorhandenen Restsauerstoffgehalt ab, so dass die sonst an der Oberfläche der Stahlprobe stattfindende Oxidation beinahe vollständig unterbunden wurde. Auf diese Weise lassen sich die Austenitkorngrenzen kohlenstoffarmer Stähle deutlich darstellen. Die beschriebene Methode lässt sich auf Stähle eines weiten Zusammensetzungsbereiches anwenden.
Herausforderungen bei der Präparation von metallischen Hybridwerkstoffen
Authors: Schiffl Andreas , Fragner Werner , Kainhofer Christa , Papis Konrad
Published: December 2013

Kurzfassung

Die Präparation von monolitischen metallischen Werkstoffen für die spätere metallografische Bewertung ist gängige Praxis. Die Schliffherstellung von Werkstoffhybriden ist allerdings schwieriger. Gründe hierfür sind unterschiedliches Werkstoffverhalten hinsichtlich mechanischer Beanspruchung (Abrasion beim Schleifen und Polieren) sowie chemisches Verhalten bei anschließenden Ätzungen.

Werkstoffverbunde werden allerdings immer öfter sowohl im wissenschaftlichen als auch im industriellen Umfeld nachgefragt und eingesetzt. Um die Qualität dieser Werkstoffverbunde, insbesondere die der Fügestelle, zu prüfen und zu charakterisieren werden diese Verbunde metallografisch untersucht. Daher ist eine Adaption der metallografischen Verfahren an das jeweilige System notwendig.

Dieser Artikel beschäftigt sich mit der Charakterisierung des Systems Aluminium-Eisen und der etwaigen auftretenden intermetallischen Phasen, auch im Mehrkomponentensystem bei Legierungen.

Die dabei auftretenden Herausforderungen werden dargestellt und anschließend eine Verfahrensroute zur Erstellung hochqualitativer Ergebnisse für die Beurteilung des Verbunds vom Schliff bis zur rasterelektronischen Aufnahme aufgezeigt.
Objektbasierte quantitative Analyse von komplexen Mikrostrukturen in Stählen
Authors: Fischer Martin , Gerdemann Florian , Bleck Wolfgang , Schwedt Alexander
Published: December 2013

Kurzfassung

Ein neues Verfahren zur quantitativen Bildanalyse von komplexen Mikrostrukturen in Stählen wird vorgestellt. In modernen Stahlgüten ist der Zugang zu quantitativen Informationen über Form, Textur und Kontext der mikrostrukturellen Bestandteile durch die zunehmende Komplexität und Verfeinerung der Gefüge mit den aktuellen metallografischen Analysemethoden nur mit erheblichem Aufwand möglich. Das vorgestellte Verfahren arbeitet objektbasiert, d.h. anstatt Bildpunkte einzeln und isoliert zu betrachten, werden zunächst die Beziehungen der Pixel untereinander analysiert. Als zusammengehörig erkannte Pixel werden zu Gruppen, sogenannten “Bildobjekten“, zusammengefasst. Diese spiegeln Formen und Aufbau der realen Gefügestrukturen wieder und ermöglichen es, den Zugang zu Daten über Geometrien, graphische Texturen und die räumliche Anordnung der Gefügebestandteile zu gewinnen. Mit Hilfe dieser zusätzlich zu den spektralen Werten der Pixel verfügbaren Daten wird die quantitative Analyse von komplexen Gefügen ermöglicht. Dies wird an REM-Bildern verschiedener Stahlgüten demonstriert.
Metallographic Characterization of Additive-Layer Manufactured Products by Electron Beam Melting of Ti-6Al-4V Powder
Authors: Murr Lawrence E. , Gaytan Sara M. , Lopez Maria I. , Martinez Edwin , Medina Francisco , Wicker Ryan B.
Published: December 2013

Optical metallography and electron metallography (SEM and TEM) techniques are applied to the characterization of additive-layer manufactured products and prototypes by electron beam melting (EBM) of Ti-6Al-4V atomized precursor powder. In addition, microstructure-property comparisons are made by hardness and tensile test measurements which demonstrate prospects for controlled property-performance variations by varying process parameters including temperature profiles and cooling rates in manufactured prototypes.
Co-site Microscopy: Case Studies
Authors: Paciornik S. , Gomes O. D. M.
Published: December 2013

A new methodology, co-site microscopy, is presented and discussed through a set of case studies. Images from the same field, or set of fields, of a sample are acquired with different microscopy techniques, or from the same microscope in diverse contrast modes and/or sample conditions. The obtained data is assembled in a multi-modal database that provides better statistical accuracy than traditional quantitative metallography approaches, while tracking local changes in the sample. Case studies on automotive catalysts, a copper ore, and a cast iron are presented and discussed.
Schäden an Brennerkomponenten von Heavy Duty-Gasturbinen
Authors: Neidel Andreas , Matijasevic-Lux Biljana , Riesenbeck Susanne , Ullrich Thomas , Völker Jörg , Wallich Sebastian
Published: December 2013

Kurzfassung

Brenner sind Schlüsselkomponenten in Turbomaschinen mit interner Verbrennung. Sie ermöglichen in Großgasturbinen für Kraftwerke eine besonders magere Verbrennung und tragen so wesentlich zum wirtschaftlichen Betrieb bei. Abhängig vom Design sind sie häufig statisch und dynamisch hoch beansprucht. Bei der Fertigung dieser sowohl geometrisch als auch werkstofftechnisch komplexen Bauteile spielen schmelzschweisstechnische Fügeverbindungen eine wichtige Rolle. An drei ausgewählten Schadensbeispielen, die mit gerissenen Schweissnähten in Zusammenhang stehen, wird gezeigt, dass fast immer eine Kombination mehrerer Ursachen schadensauslösend wirkt. Besonderer Wert wird dabei auf die Betrachtung konstruktions-, fertigungs-, montage- und betriebsbedingter Einflüsse und Ursachen gelegt. Die als Datenträger wichtigen Bruchflächen der Schadensteile zeigen in den vorgestellten Fällen Schwingbrüche und Heißrisse als werkstofftechnische Versagensmechanismen.
Mechanical and Microstructural Behaviour of Dissimilar Aluminum Alloys Joined by Friction Stir Welding
Authors: Sayer Sami , Yeni Çinar , Kuşoğlu Murat
Published: December 2013

In this study, joining of dissimilar aluminum alloys 5059-H111 and 7075-T651 was carried out using friction stir welding. The joint has been investigated in terms of microstructure, hardness and mechanical properties. Optical microscopy was used to characterize the microstructure of the weld area. Seven different zones of the microstructure in the joint can be distinguished. It has been observed that a fine grain structure is formed in the nugget zone as a result of recrystallization. Although there is a general hardness decrease throughout the weld region compared to both base metals, the lowest hardness values are seen at the heat affected and thermo mechanically affected zones of aluminum alloy 5059. The mechanical strength of the dissimilar joint was found to be varying between 56 % to 68 % those of the base metal ultimate tensile strength values. The results show that friction stir welding can be successfully applied for the joining of dissimilar aluminums alloys.
Effect of Mg on Mechanical Properties of Al-Mg Alloys
Authors: Çaydaş Ulaş , Hasçalik Ahmet
Published: December 2013

In this study, the effect of Mg content on the mechanical properties of Al-Mg alloys was investigated. For this, five different alloys were produced by conventional casting method. Tension, Charpy and fatigue tests were carried out and hardness measurements were conducted on the alloys. Fatigue tests were performed using a rotational bending fatigue test machine and the fatigue strength has been analysed by drawing S-N curves and critically observing fatigue fracture surfaces of the tested samples. The microstructure of the alloys and fracture surfaces were examined by optical and scanning electron microscopy (SEM). The experimental results indicate that mechanical properties are significantly affected by the addition of Mg and the fatigue strength of samples increased due to solid solution strengthening with increasing Mg content in chosen conditions.
Study of Microstructural Evolution of X4CrNiSiTi14-7 During Thermal Aging
Authors: Sakhawat Shahroz , Falahati Ahmad , Domankova Maria
Published: December 2013

Microstructural evolution during aging treatment in a high tensile precipitation hardening stainless steel (X4CrNiSiTi14-7) has been investigated. Matrix consists of martensitic structure and the combined addition of Si and Ti causes an intermetallic phase type Ni16Ti6Si7 that precipitates with-in grains and enhance precipitation strengthening. This material shows a good combination of high strength and ductility.

Light-Optical microscopy, electron back scattered diffraction, transmission electron microscopy and X-ray diffraction analysis have been used to study the microstructural evolution during aging. It has been found that precipitations of various kinds are taking place during aging treatments including nm-scaled G-phase and various carbides. Higher aging temperatures lead to reverse transformation of martensite to austenite.
3D Interpenetrating Hybrid Network of Rigid Phases in an AlSi10Cu5NiFe Piston Alloy
Authors: Asghar Z. , Requena G. , Boller E.
Published: December 2013

The three dimensional architecture of an AlSi10Cu5NiFe piston alloy in as-cast condition is characterized qualitatively and quantitatively by means of synchrotron tomography and light optical tomography. The same sample is used to correlate and combine the results obtained using both techniques. Synchrotron tomography reveals the long-range interconnectivity, volume fraction and shape of different aluminides present in the studied alloy. The morphology of individual aluminides and their contiguity between each other as well as with the eutectic Si is studied by light optical tomography. The eutectic Si and the Fe-aluminides show a considerable fraction of regions with platelet-like morphologies while the Cu-aluminides and Ni-aluminides show a large fraction of region with convex saddle and convex cylindrical morphologies. The aluminides and the eutectic Si form ≈ 18 vol. % three dimensional hybrid network with a long-range contiguity and interconnectivity located in the interdendritic space.
The Microstructure and Hardness Properties of ZrO2+Y2O3/Al2O3 Layers Coated by Using Plasma Spray Process on Al Bronze Surface
Authors: Özel Serkan , Turhan Hüseyin
Published: December 2013

In this study, ZrO2 + Y2O3/Al2O3 powders were coated on the surface of aluminum bronze (Cu + 5 % Al) by using the atmospheric plasma spraying method. The effect of Al2O3 on microstructure and hardness was examined in four different coatings applied by using 5-10-20 % Al2O3 ratio in ZrO2 + Y2O3 and ZrO2 + Y2O3. For this purpose, microstructure images of the coated layers were taken in optical microscope and SEM, EDX and XRD analyses were performed and their microhardness values were measured. It was observed that a porous structure occurred in the coatings containing ZrO2 + Y2O3/Al2O3. The coatings containing Al2O3 showed higher microhardness values than the one without Al2O3, and depending on the increase of Al2O3 amount, the amount of porosity increased and microhardness value decreased.
Effect of Sn on the Characteristic Solidification Temperatures of AlSi6Cu4 Alloy
Authors: Djurdjevic M. , Muche D. , Stauder B. , Eigenfeld K.
Published: December 2013

The solidification path of AlSi6Cu4 alloy with various content of Sn has been investigated using cooling curve techniques. The content of Sn has been varied from 0 to 500 ppm. The hardness of as cast alloys with different content of Sn has been measured. The results show that Sn in synthetically designed AlSi6Cu4 alloy (very low level of other elements) precipitate isolated. The increased content of Sn decreases significantly the solidus temperature of this alloy, prolonging its solidification temperature interval for approximately 9K. The hardness of this alloy has been reduced for about 20% by presence of Sn up to 500 ppm.
Influence of the Metallic Die Graphite Layer Thickness in the Microstructure of Aluminium Bronze Alloy
Authors: Cenoz Isaac
Published: December 2013

The phases obtained in copper aluminium bronze alloy (Cu-Al10-Fe2) cast into a permanent die were investigated. The parameters examined were the pre-heating temperatures of the die and the graphite coating thickness. The phases α and γ2 were detected as well as the metastable phases β’ and γ’. The intermetallics of the system Fe-Al were obtained in various stoichiometric compositions. The different cooling rates of the casting resulted in two mechanisms of transformation to α grains out of the unstable β phase, one being nucleation and growth producing needle shaped α grains, the other exhibiting a massive transformation to spherical α grains. These two mechanisms determine the changes in the size of the α grains as a result of changes in the cooling rate in its various ranges.
Materials Technology for Advanced Land Based Gas Turbines
Authors: Matijasevic-Lux Biljana , Neidel Andreas
Published: December 2013

Gas turbines have found increasing application in electric power generating plants in addition to the established applications for aircraft and marine propulsion. The success of the gas turbine in these applications has led to demands for units with increased power output but the development of engines designed to meet these demands has presented difficult technological problems.

In modern gas turbines engines, engine firing temperatures still constantly increase in order to improve the thermal efficiency of these machines. These targets are met through the use of advanced designs, materials, and coatings for hot gas path components.
Zementitnachweis zur Unterscheidung von Bainitstufen in modernen, niedriglegierten Mehrphasenstählen
Authors: Miyama Elisabeth , Voit Christina , Pohl Michael
Published: December 2013

Kurzfassung

Bainitische Gefügeausprägungen kommen bei modernen, niedriglegierten Mehrphasenstählen verstärkt vor. Die Kenntnis der Bainitausprägung in Abhängigkeit der Legierungskonzepte und Herstellrouten ist wichtig, um entsprechende Festigkeitsniveaus gezielt einzustellen. Dabei spielt vor allem die Ausscheidungsmorphologie von Zementit eine entscheidende Rolle, um eine eindeutige Phasenzuordnung treffen zu können. Zur Darstellung und Auswertung der submikroskopischen Zementitausbildung wird bis dato die zeit- und damit kostenaufwändige Durchstrahlungselektronenmikroskopie (TEM) verwendet.

Die vorliegende Arbeit zeigt, dass es durch Optimierung und Anwendung einer geeigneten Präparations- und Abbildungstechnik auch mit hochauflösender Rasterelektronenmikroskopie möglich ist, die Ausscheidungsmorphologie des Zementits in bainitischen Gefügen gut darzustellen und zusätzlich quantitative Kennwerte, wie Teilchenlänge, -anzahl, sowie -verteilung auszuwerten. Die optimierte Präparations- und Abbildungstechnik ermöglicht es künftig, im Vergleich zum TEM umfangreichere, statistisch abgesicherte und somit auch kostengünstiger Untersuchungen zur Zementitausbildung durchzuführen.
Materialographische Untersuchungen an Dentalwerkstoffen
Authors: Behrend Detlef , Warkentin Mareike , Specht Olaf , Schmidt Wolfram , Rosentritt Martin , Ottl Peter
Published: December 2013

Kurzfassung

Aufgrund der demographischen Entwicklung steigt der Bedarf an geeigneten Werkstoffen und Biomaterialien für die Zahnerhaltung und auch für den Zahnersatz kontinuierlich. Im Fokus stehen hierbei Werkstoffe, die aufgrund ihrer physikochemischen, mechanischen und biologischen Eigenschaften die Qualität und Langlebigkeit in den Bereichen der minimalinvasiven Prophylaxe, Füllungstherapie, zahnärztlichen Prothetik und Implantologie signifikant verbessern. Nur durch die Kombination verschiedener mikroskopischer Untersuchungsverfahren ist es möglich, die Struktur-Eigenschaftskorrelation detailliert zu untersuchen und zu charakterisieren. Somit können die Funktionalitätsparameter der Werkstoffe optimiert werden, um dentale Werkstoffe mit optimierten Eigenschaften zu entwickeln.
Effizienteres Aushärten UV-sensitiver Einbett-Materialien
Authors: Amrhein Frank , Kehrer Martin , Schreck Timo , Bochtler Ulrich , Hellmann Ralf , Kaloudis Michael
Published: December 2013

Kurzfassung

Im nachfolgenden Artikel wird eine neuartige Vorgehensweise zum Aushärten von UV-sensitivem Einbettmaterial mittels Leuchtdiodentechnologie beschrieben. Durch den Einsatz monochromatischer UV-Strahlung war es möglich, die Aushärtezeiten im Vergleich zur Aushärtung mit konventionellen Quecksilberdampflampen drastisch zu reduzieren. Weiterhin konnte die minimal notwendige Bestrahlungsdosis für die jeweils untersuchte Einbettmasse bestimmt und eine materialspezifische Kenngröße berechnet werden, wodurch die Ermittlung der exakten Aushärtezeit für eine vollständige Aushärtung möglich ist.
Examination of the Mg-Zn Phase Formation in Hot-Dip Galvanized Steel Sheet
Authors: Zywitzki O. , Modes Th. , Scheffel B. , Metzner Ch.
Published: December 2013

Zinc-magnesium layers have been produced by a combination of conventional hot-dip galvanizing and PVD magnesium coating. A subsequent short heat treatment causes the diffusion of magnesium into the zinc layer. The influence of the maximum temperature of the heat treatment on the diffusion of magnesium and on the type and distribution of the formed intermetallic Mg-Zn phases has been examined in detail in a temperature range from 300 to 400°C by means of X-ray phase analyses and metallographic cross sections. With increasing temperature a sequential intermetallic Mg-Zn phase formation has been detected. At 300°C, an initial magnesium rich, intermetallic MgZn2 surface layer is formed, which, at higher temperatures from 335 to 379°C, is progressively transformed into a zinc rich Mg2Zn11 layer by interdiffusion. In this context, the nucleation of the Mg2Zn11 phase takes place on the interface between the MgZn2 and the Zn phase. Above the peritectic temperature of 381°C, the microstructure is composed of a zinc matrix in which precipitated MgZn2 is dispersed.
Detection of Dendrite Coherency Temperature of Aluminum Alloys Using Single Thermocouple Technique
Authors: Djurdjevic M. , Odanovic Z. , Zak H.
Published: December 2013

The dendrite coherency point (DCP) temperature refers to the state of a solidifying alloy at which a coherent dendrite network is established during the formation of grains. There are three main approaches for detection of DCP: (i) the thermal analysis method, (ii) mechanical (or rheological) technique and (iii) physical method based on the thermal diffusivity measurement technique.

There are two basic variants of the thermal analysis method. In the late 1980's Bäckerud developed a method that utilizes two thermocouples. The DCP is determined by identifying the point of minimum temperature difference at the δT curve (TW–TC). Recently, has been revealed that utilization of the first derivative curve (dT/dt) plotted versus temperature also allows for analysis of the α-Al dendrite nucleation and growth characteristics and consequently determination of the DCT. This paper will illustrate that the dendrite coherency temperature could be identified by the 1st derivative curve (the one-thermocouple method) with the same accuracy as well as by using two thermocouples technique.
Liquation Cracks in Hot Upset Low Alloy Steel Screw Heads
Authors: Neidel A. , Riesenbeck S.
Published: December 2013

A thermally upset screw head had numerous cracks at the intersection screw head / screw shaft. The screw consisted of steel that usually does not tend to hot crack. The screw failed when tightening it by applying a torque lower than the nominal torque. The screw head was simply sheared off.

A hot crack has clearly been identified as damage-causing mechanism of the material, or, more precisely, liquation cracks. Other damage hypotheses such as liquid metal induced stress corrosion cracking have reliably been excluded in the course of examinations.

The material used was 1.7711, 40CrMoV4–6, a material especially used for creep resistant fasteners such as screws and nuts for operating temperatures up to 540°C. This material belongs to the group of low alloy chromium molybdenum vanadium steels. It is typically used in the tempered condition. In Europe, it corresponds to standard EN 10269. In the USA, this steel is known as ASTM A193 GR B16.
Sample Preparation by Metallography and Focused Ion Beam for Nanomechanical Testing
Authors: Moser G. , Felber H. , Rashkova B. , Imrich P.J. , Kirchlechner C. , Grosinger W. , Motz C. , Dehm G. , Kiener D.
Published: December 2013

Mechanical size effects in micron and submicron scale sample testing are of immense interest in materials science. In this work, we report on a combination of structured chemical etching and focused ion beam fabrication to allow site specific and time efficient fabrication of miniaturized specimens for mechanical testing. Further, we demonstrate the applicability of these samples for quantitative in situ experiments in the scanning and transmission electron microscopes.
Assessment of Some Methods for Grain Size Measurement
Authors: Markoli B. , Naglič I. , Prosenc M. , Kuhar V.
Published: December 2013

Due to the fact that grain size measurement in metallic materials is of great importance, five well known and established grain size measurement methods were compared for accuracy and time consumption, i. e.: comparison method, intercept method, planimetric method (by Jeffries), planimetric delineation method performed in semiautomatic manner and automatic method (commercial software by ZEISS). For that purpose standard low-carbon ferritic steel (W. NR. 1.0360), austenitic steel (W. NR. 1.4404) with two different grain sizes (denoted as A and B) and nodularized grey cast iron (EN-JS 1082) were chosen.

It was discerned that the comparison method represents the fastest solution for the grain size measurement but it is limited in precision and applicability in two phase materials. The automatic (commercially available software) method was proved to be unreliable, while the intercept method or one of the planimetric methods is the most reasonable choice when higher accuracy is required.
Corrosion Damage to a Dropped Handlebar Made of AA7075
Authors: Schneider M. , Langklotz U. , Sempf K.
Published: December 2013

Damage by corrosion was discovered on a dropped handlebar made of AA7075 during an inspection at a workshop. The possible causes are presented and the corrosion types encountered are interpreted. Stress corrosion or corrosion fatigue under the effect of chloride can be concluded from the damage pattern and reconstructed conditions of use. The heterogeneous microstructure containing a large number of intermetallic precipitates accelerates the start of corrosion because microgalvanic elements are formed. Although aluminium alloys, when in an urban environment, do not exhibit a pronounced tendency to corrosion the conditions of corrosion can locally change in use to such an extent that corrosion damage will occur. In the present case, a remedy can primarily consist in inspections at well-adapted intervals and the exchange of the handlebar tape in good time.
Oxidation and Mechanical Behaviors of Two Phase (Mo + T2(Mo5SiB2)) and Three Phase (Mo + T2(Mo5SiB2) + Mo3Si) Alloys at 1 073 K and 1 373 K
Authors: Park J. S. , Kim J. M. , Kim H. Y.
Published: December 2013

The oxidation behaviors of Mo rich alloys have been investigated in the Mo-Si-B ternary system. Seven selected alloy systems composed of two phase alloys (Mo (solid solution) + T2 (Mo5SiB2) and three phase alloys (Mo (solid solution) + T2 (Mo5SiB2) + Mo3Si) have been fabricated by arc melting elemental components. Mechanical behaviors of the selected alloy systems have been investigated in order to identify the effect of composition on the ternary system. Also, oxidation tests have been performed in order to identify the oxidation behaviors at 1 073 and 1 373 K. When the alloy compositions move towards the Mo side, the oxidation reactions were accelerated for the two phase alloys due to the presence of Mo (s. s.), while the tendency of oxidation was not fast for the three phase alloys. The oxidation behaviors at above and below 1 273 K have been discussed in terms of microstructural observations during oxidation tests.
Application of Complementary Techniques for Advanced Characterization of White Etching Cracks
Authors: West O. H. E. , Diederichs A. M. , Alimadadi H. , Dahl K. V. , Somers M. A. J.
Published: December 2013

White etching crack (WEC) networks were characterized in heavy loaded bearings for wind turbines. Both conventional techniques as reflected light microscopy and (scanning and transmission) electron microscopy as well as electron backscatter diffraction and ion channelling contrast imaging were applied. The complementary use of the techniques in unravelling the complicated failure mechanisms is explored in the present work.
Study of the Impact of Multiple Weld Repairs and Associated Stress-Relief Annealing on Mechanical Properties at Elevated Temperatures of Large Components Made of the Low-Alloy Steel 16Mo3
Authors: Giller M. , Lehmann K.
Published: December 2013

This paper is related to 16Mo3, a low-alloy steel typical in the manufacture of large welded steel casings of heavy-duty gas turbine engines. The usual practice in manufacturing is to stress relieve these housings after fabrication welding. If, however, weld imperfections are detected by non-destructive testing, weld repairs are performed, followed by additional stress-relief heat treatments. The methods applied were used to detect possible embrittlement by secondary carbide precipitation and to finally draw conclusions on material changes. The critical area of a weld is the heat affected zone. In this area a worsening of the stress condition in connection with a change in carbide precipitation and thus a decrease in creep rupture strength occurs. A concrete alloy composition and heat treatment adapted to the precipitation behavior are important, because they determine the type, amount and distribution of the resulting carbides [1, 2].
Polymer/Layered Silicate Nano-composites
Authors: Okamoto M.
Published: December 2013

Polymer/layered filler nano-composites (PLFNCs) offer remarkably improved mechanical properties with low inorganic filler loading. Major developments in this field have been carried out over the last one and half decades. However, we are far from the goal of understanding the mechanisms of the enhancement effects in nanocomposites. Continued progress in nanoscale control, as well as an improved understanding of the physicochemical phenomena at the nanometer scale, has contributed to the rapid development of novel PLFNCs. We describe nano-structure development and processing operations in PLFNCs.
The Effect of Post-extrusion Conditions in Ribbon Extrusion of Polymer Blends
Authors: Ramirez-Arreola D. , Padilla-López H. , González-Núñez R. , Rodrigue D.
Published: December 2013

Blends of high density polyethylene and polystyrene were produced via ribbon extrusion to study the effect of post-extrusion conditions on the ribbon final dimensions and morphology. An experimental setup was designed to measure the stretching force as a function of draw ratio and water contact distance for blends of 3, 6 and 9% PS in HDPE. Numerical simulations of the non-isothermal process using Matlab were in good agreement with the experimental data only when both viscous and elastic effects are included. The results show that both draw ratio and water contact distance have a definite influence on the final dimensions of the ribbon and the stretching force. It was found that deformation of the dispersed phase increases with draw ratio, but decreases with water contact distance.
Microcellular Wood Fibre Reinforced PP Composites
Authors: Bledzki A. K. , Faruk O.
Published: December 2013

Microcellular wood fibre reinforced polymers have practical significance given the possibility of reducing the density of automotive components due to their microcellular structure, as well as processing and performance advantages. A microcellular foaming process with a chemical foaming agent was applied at an experimental stage to injection moulding, extrusion and compression moulding of wood fibre reinforced polypropylene composites. The focus of the research was to investigate these processes using a chemical foaming agent and to perform comparative studies of the physico-mechanical properties of microcellular materials. The effects of the presence of the chemical foaming agent (exothermic) and variation of its content on density, microvoid content, mechanical properties (tensile and flexural), odour concentration and cell morphology of microcellular polypropylene-wood fibre composites were studied. The morphology, cell size, shape and distribution of the microcells were investigated using scanning electron micrographs. Injection moulding process produced finer microcellular structures in comparison with the other processes. As compared to the non foamed composites, the density reduced maximum 30% (0.741 g/cm3), 20% (0.837 g/cm3) and 22% (0.830 g/cm3) for the injection moulding, extrusion and compression moulding process respectively. The chemical foaming agent reduced the odour concentration in relation to the same non foamed composites. Injection moulding showed better performance in comparison with extrusion and compression moulding in terms of cell morphology, density reduction, odour concentration and mechanical properties.
A Low Force Valve for Dynamic Control of Molten Plastics in a Mold
Authors: Kazmer D. O. , Gupta D.
Published: December 2013

Polymer processing has been limited by the lack of direct flow and pressure control of the polymer melt at multiple points in space and time. Improved axial and radial valve designs are discussed that require negligible actuation force to control the flow of the pressurized melt. The forces resulting from pressure loads and shear stresses are first analyzed for an axial valve pin. Subsequently, a radial valve design is implemented and experimentally characterized using neat polycarbonate. A sigmoidal response surface is fit to the experimental data and found to very well model the observed pressure drop as a function of flow rate and valve pin position. The juncture loss at the valve port is then characterized by estimating and removing the pressure drops in the circular flow segments of the valve. Analysis indicated that the juncture loss is inversely proportional to the exposed area, or vesica piscis, formed between the circular flow channel in the valve body and the flow port on the moving valve pin. While applicable to many different polymer processing operations, the validated models are used to show the dynamic valve pin position as a function of the desired flow rate and desired cavity pressure in the hot runner of an injection mold. Finally, the impact of the designs on lower power, more compact mechanical and control system designs are discussed.
Influence of Drawing and Temperature on the Optical and Structural Properties of Monofilament PP Sutures
Authors: Seisa E. A.
Published: December 2013

The influence of drawing and temperature on the optical and structural properties of monofilament polypropylene sutures (PP) were investigated using interferometry. Two techniques have been used in this study: 1) the polarizing interference microscope, 2) multiple-beam Fizeau interferometry. The polarizing interference microscope is used to study the variation of refractive indices and birefringence of PP sutures at different draw ratios and stresses. The stress-strain diagram of PP sutures was studied. The resulting data was used to calculate the average work per chain, Poisson's ratio, strain optical coefficient, Young's modulus and optical orientation function. Multiple-beam Fizeau interferometry was used to study the temperature effect on optical properties of PP sutures with temperature ranging from 19 to 40°C. Relationships between the optical parameters at different temperatures are given. Calculation of the density, crystallinity, dielectric constant and dielectric susceptibility at different temperatures are done. The results obtained, clarify the effect of drawing and temperature on the structure of PP sutures. Microinterferograms are given for illustration.
A New Calculation Model and Optimization Method for Maddock Mixers in Single Screw Plasticising Technology
Authors: Zitzenbacher G. , Karlbauer R. , Thiel H.
Published: December 2013

A homogenous melt is the prerequisite to achieve the demanded product quality in single screw plasticising technology. At higher screw speeds and mass flow rates solid particles can occur in the melt. Dispersive mixing elements are often used to improve the melt quality. Calculation models are necessary for designing mixing elements in the right way. A new model for the often used fluted mixing sections like axial and spiral Maddock-elements and Z-elements is presented in this paper.

The calculation model is reduced to a single pair of inlet and outlet flute, connected by the shearing gap. Especially in spiral Maddock mixers the longitudinal flow in the flutes is a combined pressure and drag flow but in axial Maddock mixers pure pressure flow occurs. In the shearing gap a combined pressure and drag flow can occur. The leakage flow through the flight clearance is also considered.

Geometry functions are introduced for considering the rectangular or circular segment shaped cross section of the flutes. The viscosity is shear rate and temperature dependent, the channel height as well as the channel width can vary along the mixing element. The model allows the calculation of the longitudinal pressure profile in the inlet and outlet flutes, the total pressure drop and the shear stress distribution in the shearing gap.

Mixing sections sometimes show a too high pressure consumption and insufficient shearing efficiency. Therefore a geometry optimization method for axial Maddock mixing heads is presented in this paper.
Investigations into Kinematic Reversal in Non-isothermal Flows in Single-screw Machines
Authors: Potente H. , Bornemann M. , Heinrich D. , Pape J.
Published: December 2013

When describing the flow in single-screw machines in mathematical terms, the screw is generally assumed to be standing still inside a rotating barrel. This study looks into whether and, if so, how far this principle of kinetic reversal falsifies the calculation result. It is performed both on an analytical basis and with the aid of comparative FEA simulations, taking the general case of a non-isothermal flow. It is shown that both kinematic boundary conditions lead to absolutely identical calculation results.
Residual Wall Thickness Distribution at the Transition and Curve Sections of Water-assisted Injection Molded Tubes
Authors: Liu S.-J. , Hsieh M.-H.
Published: December 2013

Water-assisted injection molding technology has been used to manufacture plastic tubes in recent years, due to its light weight, relatively lower resin cost per part and faster cycle time. The residual wall thickness around dimensional transitions and curved sections can significantly affect the strength of molded parts and is of great concern. This research investigated the uniformity of the residual wall thickness distribution in water-assisted injection molded circular tubes with dimensional variations and curved sections. Experiments were carried out on an 80-ton injection-molding machine equipped with a lab scale water injection system, which included a water pump, a pressure accumulator, a water injection pin, a water tank equipped with a temperature regulator, and a control circuit. The material used was semi-crystalline polypropylene. It was found that the wall thickness was not uniform near transitions. With the addition of fillets with proper angles around transitions, the uniformity of residual wall could be greatly improved. The residual wall thickness in curved sections was thick around the outer wall and thin around the inner wall. In addition, the experimental results suggest that water-assisted molded parts exhibit a more uniform thickness distribution at transition and curved sections than in gas-assisted molded parts.
Correlation between Injection Molding Parameters, Morphology and Mechanical Properties of PPS/SEBS Blend Using Artificial Neural Networks
Authors: Lotti C. , Bretas R. E. S.
Published: December 2013

The objectives of this work were to identify the injection molding processing variables with the greatest effect on the morphology and mechanical properties of an injection molded blend made of poly (p-phenylene sulphide), PPS and block copolymer styrene-ethylene-butadiene-styrene ‘SEBS’. Artificial Neural Networks, ANNs, are used as an alternative method to constitutive and empirical models, to predict morphological features and mechanical properties from the injection molding conditions, and to predict mechanical properties from the morphological features.

The quantification of SEBS dispersion in the PPS matrix was done using a dispersion function. Mold temperature and flow rate were the processing variables with the highest influence on the entire morphology, while the holding pressure influenced mainly the inner layers. Impact strength and toughness were most influenced by mold temperature, holding pressure and the outer layers. The flexural modulus was influenced by all processing variables and the intermediate layers.

Three different ANNs were evaluated: one (ANN-1) to predict morphology from processing conditions and another two to predict mechanical properties from morphology and from processing conditions (ANN-2 and ANN-3, respectively). These latter ANN models had similar results, indicating that both inputs could be successfully used to predict mechanical properties, as the mean residuals were close to experimental errors. On the other hand, ANN-1 showed a lower performance, with a mean error smaller than the experimental error, suggesting that ANNs could overtake some inherent uncertainties.

In this case, it was concluded that the distribution of data along output domain was more important than a high number of training data in the ANN's performance.
Dynamic Mold Surface Temperature Control Using Induction and Heater Heating Combined with Coolant Cooling
Authors: Chen S. C. , Jong W. R. , Chang J. A. , Chang Y. J.
Published: December 2013

In this study, both electrical heater heating and electromagnetic induction heating combined with coolant cooling are developed to achieve a dynamic mold surface temperature control. Simulation tool was also developed by integration of both thermal and electromagnetic analysis modules of ANSYS. The capability and accuracy of simulations on the heater heating and induction heating were verified with experiments. To evaluate the feasibility and efficiency of heater heating and induction heating on the mold surface temperature control, a mold plate, roughly about an inset size of cellular phone housing, installed with five heaters and designed with four cooling channel with coolant running through, was utilized for the demo experiments varying mold surface temperature between 110 °C and 200 °C. During induction heating/cooling case, it takes 4 s to increase mold surface temperature from 110 to 200 °C and it takes another 21 s for mold surface to cool down to 110 °C. The mold plate surface temperature can be raised at about 22.5 °C/s and cooled down at 4.3 °C/s within the mentioned temperature range. Mold plate temperature distribution exhibits good uniformity as well in all stage of heating/cooling process. For heaters heating, it takes 37 s to increase mold surface temperature from 110 to 200 °C and it takes another 30 s for mold surface to cool down to 110 °C. The temperature rising rate is only about 2.4 ° C/s. Induction heating is more efficient in mold surface temperatures control than electrical heating and it does eliminate the weld line mark when applied to a tensile test mold with double gate design prior to melt injection.
Visualization of Melt-Flow Behavior Inside the Runner in Ultra High Speed Injection Molding
Authors: Hasegawa S. , Yokoi H.
Published: December 2013

Ultra-high-speed injection molding is a highly effective technique for realizing very thin-walled molded parts; its application to the production of new high value-added products is anticipated. The melt-flow behavior in ultra-high-speed injection molding is expected to differ from that in conventional molding. However, thus far, very few studies pertaining to the phenomena occurring within cavities and runners at such high filling speeds have been reported, thus necessitating the direct observation of melt-flow behavior inside the molds.

In this study, we attempted to dynamically visualize the melt-flow behavior at the runner split portion, especially under ultra-high-speed injection molding. Visualization experiments were conducted using a glass-inserted mold, which was modified from the original visualization mold structure in order to improve the pressure endurance of the glass-inserted visible area. This paper discusses the visualization analyses of melt-flow behavior in two types of experimental split runner systems (three inclined split runners and cross-shaped runners in a cascade layout). The behavior at the runner split area was studied under low to ultra-high-filling rates. The analyses clarified the effects of inertia at the runner branching point, which has not been verified in general injection molding, and the consequent changes in the filling behavior.
A New Scheme for Controlling Part Cooling in Injection Molding
Authors: Hernandez J. M. , Dubay R. , Pramujati B.
Published: December 2013

Part cooling parameters such as coolant flow rate and coolant temperature has been shown to have an important influence on the part quality in plastic injection molding. Molders commonly manipulate the coolant flow rate in an unclear manner to adjust part quality and reduce the overall cycle time. Manipulating such parameters effectively can indirectly control part quality when deviations in the injection processing variables occur if it is done in a controlled manner. In this investigation, coolant flow rate is selected to be the manipulated variable that affects an average temperature of the part surface as it cools within the mold cavity. The average part temperature is the controlled variable and its control represents the indirect control of part quality. Experiments were conducted to quantify the effects of coolant flow rate on the part surface temperature demonstrating that it is highly nonlinear and its control would require an advanced control scheme. An adaptive online modeling algorithm that uses information from temperature and flow rate sensors was developed to continuously retune a predictive controller for controlling the part surface temperature. Good control performance was obtained from the adaptive strategy for tracking setpoint changes in the part temperature and when the cooling cycle was reduced from 16 to 14 s.