bluuebunny/crossref_metadata_2025 huggingface dataset:
Elektronenmikroskopische Untersuchung der Mikrostruktur von pseudoelastischen NiTi-Stents
Authors: Frotscher M. , Kröger A. , Somsen Ch. , Neuking K. , Steegmüller R. , Schüßler A. , Eggeler G.
Published: December 2013

Kurzfassung

Nickel-Titan-Formgedächtnislegierungen (NiTi-FGL) werden seit einigen Jahren kommerziell erfolgreich eingesetzt. Insbesondere im Bereich der Medizintechnik gibt es zahlreiche Anwendungen, bei denen sich NiTi etabliert hat. Ein Beispiel dafür sind Gefäßprothesen (Stents). Auch wenn NiTi-Stents zur Zeit nur einen Anteil von cirka 12% der weltweit mehr als 3,5 Millionen implantierten Stents pro Jahr ausmachen, wird der Markt für endo- und kardiovaskuläre Stents 2006 ein Volumen von 5,5 Milliarden Euro überschreiten [1, 2]. Bei der Stent-Produktion entstehen Oberflächendefekte, welche unter Ermüdungsbeanspruchung zur Rissbildung beitragen können. Für die Hersteller von Stents sind daher Oberflächenqualität und Mikrostruktur mit Hinblick auf die funktionalen Eigenschaften und Ermüdungsbeständigkeit wichtige Faktoren. In der vorliegenden Arbeit wurden NiTi-Stents mit Hilfe von raster- sowie transmissionselektronenmikroskopischen (TEM) Methoden untersucht. Die Probenpräparation für TEM-Untersuchung wurde mit Hilfe einer Fokussierbaren Ionenstrahlanlage (FIB) durchgeführt, weil aufgrund der geringen Dimensionen eine andere Probenpräparation extrem schwierig ist. Dieses Verfahren wird ausführlich beschrieben und die Ergebnisse diskutiert.
Metallographic Studies on a Defective Plate Heat Exchanger
Authors: Haubner Roland , Strobl Susanne
Published: December 2013

A defective plate heat exchanger is investigated and the main aim is to find the reason for that damage and how this can be avoided. The plates are made of stainless steel (Cr17Ni12Mo2; material No. 1.4401) and are brazed with pure copper.

After cutting and examination of the heat exchanger no relevant corrosion of the copper braze is observed. Metallographic investigations by light optical microscopy (LOM) show that copper has diffused into the steel plates (liquid metal embrittlement). Using various etchings the areas of the steel plates, which are influenced by the copper diffusion, become visible and also an additional phase is observed. Electron beam micro analysis (EBMA) show that this phase is a chromium-rich ferrite.
Charactersation of the Materials and Coatings Microstructure Using FIB and Ar+-Ion Etching
Authors: Wosik J. , Sonnleitner R. , Nauer G.E.
Published: December 2013

The revealing of the materials microstructure using Ar+ Ion Etching by a Precision Etching and Coating System (PECSTM) and Focus Ion Beam (FIB) techniques is described and discussed. The advantages and disadvantages of both methods in respect to materials preparation and characterisation are demonstrated on selected samples. Different kinds of materials were chosen for investigations to give a better overview on the both methods possibilities. FIB technique is very useful for the visualisation of crystallographical defects with high disorientation angle like twins, whereas PECS reveals even small crystallographical differences (subgrains, dislocation walls) induced through plastic deformation. For the optimum performance (etching and visualisation) the knowledge of the precise etching and visualisation parameters is necessary.
Schadensanalyse an Gewindeformern
Authors: Monetti Ch. , Schemmel I.
Published: December 2013

To optimize the internal thread molding process a failure analyses was done on coated molding tools with different times of service. The investigations should provide basic knowledge for the course of failure and the failure mechanism. The observed system consists of titanium nitride (TiN) coated tools and zinced work pieces. The morphological mutation of the tool surface was observed by scanning electron microscopy (SEM). The metallographic analyses revealed the processes beyond the contact surface, the degradation of the coating and of the substrate material causes by the tribological stress, as well as the metallic microstructure. Specimen in different phases of wear have been investigated and compared with each other. The interpretation of the obtained results allowed the clarification of the failure mechanism and revealed possibilities to acquire the failure history.
Elektronenmikroskopische und metallographische Untersuchungen an supraleitenden MgB2-Bändern mit mechanisch legiertem Precursor-Pulver
Authors: Schubert Margitta , Häßler Wolfgang , Rodig Christian , Herrmann Marko , Schröder Kerstin , Holzapfel Bernhard , Schultz Ludwig
Published: December 2013

Kurzfassung

Magnesiumdiborid ist ein kostengünstiger supraleitender Werkstoff mit einer Sprungtemperatur von 40 K. Technische Leiter in Draht- bzw. Bandform werden als Verbundwerkstoff des keramischen Supraleiters in einer metallischen Hülle mittels des Pulver-im-Rohr-Verfahrens (PIT) hergestellt. Als Precursorpulver wird hochenergiegemahlenes nanokristallines Pulver bestehend aus Mg, B und partiell reagiertem MgB2 eingesetzt. Metallographische und elektronenmikroskopische Untersuchungen an verschiedenen Leitern, die sich im Hüllwerkstoff bzw. im Precursorpulver oder in den Verarbeitungsparametern unterschieden, trugen dazu bei, wichtige Schlussfolgerungen für die technologische Verarbeitung und Eigenschaftsoptimierung der Bandleiter zu ziehen. Optimierte Bandleiter zeichnen sich durch eine kritische Stromdichte von 104 A/cm2 bei 4,2 K und 10 T aus.
Analysis of Merged LOM and SEM Pictures using Innovative Image Processing Methods
Authors: Thomser Corinna , Unger Michael , Zhang Zifang , Ohm Jens Rainer , Bleck Wolfgang
Published: December 2013

Multiphase steels play an important role for the automotive industry. Their mechanical properties are strongly influenced by the microstructure. A quantitative description of the microstructure is necessary in order to optimise the properties of multiphase steels through a precise microstructure design. Using only light optical microscopy (LOM), the characterisation of multiphase steels cannot be achieved sufficiently due to the fact that very fine metallographic constituents are present, which are smaller than the optical resolution limit. This problem can be solved by using scanning electron microscope (SEM) images in addition to the light optical images.

Within this work, we describe a method for automatic composing LOM and SEM images into a single feature image. In addition, a novel segment based approach is presented, which classifies different phases in images of multiphase steels. Thereby we use several features of the derived segments for the classification process.
Abhängigkeit der formcharakteristischen Parameter Rundheit und Kompaktheit verschiedener Graphitmorphologien von der Vergrößerung
Authors: Magenreuter T. , Velichko A. , Mücklich F.
Published: December 2013

Kurzfassung

Die Unterscheidung der verschiedenen Graphitmorphologien in Gusseisen wird schon seit einiger Zeit durch bildanalytische Untersuchungen erfolgreich vollzogen und ersetzt zunehmend den subjektiven Vergleich mit Richtreihenbildern gemäß den Normen ASTM A 247–67 bzw. DIN EN ISO 945.

In vorliegender Arbeit bildete die teilchenbasierte Methode die Grundlage für weitere Untersuchungen an reinen Proben aus Gusseisen mit Lamellen-, Vermikular- und Kugelgraphit (GJL, GJV bzw. GJS) sowie an Temperguss (GJM). Im Licht- (LM) und im Raster-Elektronen-Mikroskop (REM) wurden Gefügeaufnahmen gemacht und die beiden Formparameter Rundheit und Kompaktheit für verschiedene Vergrößerungen bestimmt. Die Abhängigkeiten der Formparameter von der Vergrößerung wurden dargelegt und diskutiert.

Weiterhin waren die gewonnen Messdaten Grundlage zum Aufbau eines Klassifikators, der für beliebige Vergrößerungen des zu untersuchenden Gefüges erstellt werden kann.

Dieser Klassifikator wurde darüber hinaus an verschiedenen Gefügebildern gestestet und seine Qualität in Bezug auf die Klassifizierung verschiedener Graphitmorphologien anhand der beiden formcharakteristischen Formparameter bewertet. Es ist vorstellbar, den Parameter Vergrößerung in eine Klassifizierungssoftware mit einzubauen.
Characterization of Q & T Steel Poleshoes Manufactured by Sand Casting
Authors: Asensio-Lozano J. , Álvarez-Antolín J. F. , Panta-Mesones J. T. , Vander-Voort G. F.
Published: December 2013

This paper presents a study of the microstructural and mechanical characterization of the GS 35 CrMoV 10 4 alloy employed in the manufacture of sand-cast poleshoes for 4-pole synchronous electric power generators working at a frequency of 60 Hz. In addition, the most appropriate treatment for ensuring compliance with the technical specifications defined in DIN Standard No. 1.7755 has been designed.
Quantification of the Impact of Strontium on the Solidification Path of the Aluminum-Silicon-Copper Alloys Using Thermal Analysis Technique
Authors: Djurdjevic Mile , Byczynski Glenn , Schechowiak Carola , Stieler Hagen , Pavlovic Jelena
Published: December 2013

The impact of strontium on the solidification path of the AlSi6Cu4 aluminium alloy was examined. Strontium levels up to 210 ppm have been considered. The purpose of this study is: (i) to optimize the amount of strontium additions in AlSi6Cu4 melt in order to achieve the necessary degree of silicon modification and (ii) to observe the effects of strontium level on the other characteristic solidification temperatures of this alloy, with special emphasis on the nucleation temperature of copper rich phases. This investigation showed that a strontium level of approximately 140 ppm was sufficient to modify eutectic morphology of silicon in thermal analysis test samples. Increasing the strontium levels up to 210 ppm raises the nucleation temperature of copper rich phases, leading also to the higher area fraction of those phases.
Elektronenmikroskopische Darstellung elektrolytischer Oxidschichten auf AA2214
Authors: Schneider Michael , Kübel Christian , Yezerska Olga , Viola Alain , Augros Myriam
Published: December 2013

Kurzfassung

Die Legierung AA2214 gehört zu den mittel- bis hochfesten, aushärtbaren Knetlegierungen, die in der Luftfahrtindustrie eine wesentliche Rolle als Konstruktionswerkstoff spielen. Zum Zwecke des Korrosions- und Verschleißschutzes werden diese Legierungen sehr häufig anodisiert. Transmissionselektronenmikroskopische Untersuchungen an Schwefelsäureanodisierschichten zeigen deutlich den Einfluss der Anodisierspannung auf die Porengröße. Im Werkstoffgefüge auftretende intermetallische Phasen werden durch den Anodisierprozess weitgehend aufgelöst. Geringe Anteile an Legierungselementen sind jedoch im Oxid noch nachweisbar. Während des anschließenden Verdichtungsprozesses werden die offenen Poren verschlossen. Bereits nach 15 min ist dieser Vorgang weitgehend abgeschlossen. Dabei gibt es keine signifikante Gradierung der Verdichtung über die Oxidschichtdicke.
Mikrostrukturelle Beobachtungen bei der thermischen Ermüdung der Mg-Legierung AZ31
Authors: Krauß Martin , Scholtes Berthold
Published: December 2013

Kurzfassung

Bei der thermisch-mechanischen Ermüdungsbeanspruchung von AZ31 werden in Abhängigkeit der Zyklenzahl sowie der Temperaturamplitude bzw. der Obertemperatur charakteristische Veränderungen der Mikrostruktur beobachtet. Bei niedrigen Lastspielzahlen steht hierbei die Bildung von Gleitbändern und Verformungszwillingen im Vordergrund, während bei mittleren und höheren Lastspielzahlen neben Erholungs- und Rekristallisationsvorgängen auch Texturänderungen zu beobachten sind. Rissbildungs- und Rissausbreitungsprozesse sind eher hohen Lastspielzahlen zuzuordnen. Es werden charakteristische Beispiele gezeigt, welche die Schädigungsentwicklung in der Mikrostruktur bis zum Versagen dokumentieren.
Effect of Different Heat Treatment Conditions on the Microstructure and Mechanical Properties of Inconel 718 Nickel Based Super Alloy Used in Petroleum Production
Authors: Nascimento Jôneo Lopes do , Barbosa Cássio , Fernandes José Luiz
Published: December 2013

The development of the oil and gas industry in Brazil in the last decades has led to petroleum extraction in deeper water and extremely corrosive environments, associated to the presence of H2S, CO2 and chlorides, as well as mechanical loads caused by the wave's movement and sea streams. In these adverse conditions the search for new materials with adequate properties for this kind of application is intense.

In the present work a study is carried out on the microstructure and mechanical properties of the super alloy Inconel 718 subjected to different temperatures and times of solution and aging heat treatments. This material, usually used in the fabrication of aircraft motor and energy generation turbines, in the present case is proposed for the fabrication of bolts used in the fixation of submarine pipes for oil extraction.

The use of techniques like optical microscopy, automatic image analysis, scanning electron microscopy (SEM) and hardness and tensile tests, allowed the identification of the ideal conditions for heat treating this material for this kind of application.
The Impact of Major Alloying Elements and Refiner on the SDAS of Al-Si-Cu Alloy
Authors: Djurdjevic Mile , Pavlovic Jelena , Byczynski Glenn
Published: December 2013

This paper investigates the effect of some major alloying elements (silicon and copper) and the effect of grain refiner (titanium boride) on the size of the secondary dendrite arm spacing (SDAS) in series of Al-Si-Cu alloys. It has been shown that both silicon and copper have significant influence on this solidification parameter. The addition of grain refining master alloys to aluminium alloys is common practice in many commercial foundries aiming to reduce the grain size of Al-Si alloys. However, it was shown in the present paper that master alloy based on TiB had an unexpected impact on the SDAS, decreasing the size of SDAS. In addition, there is a minimum of SDAS corresponding to the presence of 0.12 wt% of titanium in Al-Si alloy. Such findings could have important implications for Al-Si alloys in particular, due to their wide spread applications in the automotive industry.
The Investigation of Crystallization of a-Si Films Deposited on Different Orientations by Solid Phase Epitaxy Process
Authors: Lee Kyuyoul , Kim Chungkeun , Chang Youngchul , Gall Stefan , Rech Bernd
Published: December 2013

In the experiment of this study, amorphous silicon (a-Si) films deposited by electronbeam evaporation method on (100) p+, (110) p+ and (111) p+ Si wafer substrates were crystallized at 600 °C by the solid phase epitaxy method. The times for generating the nuclei were different from one another depending on crystallized directions of the substrates, because the number of dangling bonds existing on the surface of the substrates and also the intervals of lattices are different from one another depending on the direction of crystallization. The crystallized Si film showed lots of defects. With increasing annealing time, the number of defects decreased. Also, it included more cracks. However, crystallization of the a-Si film on the (111) Si substrate was not epitaxial growth. The crystallized Si film was composed of crystal grains smaller than 1 μm.
Nutzung des instrumentierten Kerbschlagbiegeversuches zur Bestimmung von Parametern der Bruchzähigkeit
Authors: Herold H. , Streitenberger M. , Cammarota G.P. , Casagrande A. , Morri A. , Garagnani G.
Published: December 2013

Kurzfassung

Es gibt viele Ansätze zur Korrelation der Kerbschlagarbeit mit Bruchparametern. Die meisten davon liefern empirische oder halbtheoretische Gleichungen, die diesen Zusammenhang belegen.

In der vorliegenden Arbeit wird die dynamische Streckgrenze genutzt, um die Gültigkeit der Beziehung zwischen der an spitzgekerbten Proben ermittelten Kerbschlagarbeit KV [J] und der Bruchzähigkeit KIC [MPa √m] herzustellen. Dazu werden drei Bustähle (1.0570 – 1.0511 – 1.8900) und die Ti-Legierung Ti-AI6-V4 Vergleichend betrachtet.

Bei den Stählen stimmen die experimentell ermittelten Werte der Bruchzähigkeit mit denen anhand der abgeleiteten Gleichung berechneten überein. Für die Legierung Ti-Al6-V4 stimmen die Werte nicht überein, besonders nicht bei Raumtemperatur, wenn der Beitrag der α- Phase größer ist.
Mechanical Properties of Ferrochrome Based Hardfacing Layers Coated on AISI 1020 Steel Obtained by the Aid of Plasma Transfer Arc (PTA) Process
Authors: Çay Vedat Veli , Ozan Sermin , Topuz Polat , Kolukisa Sedat
Published: December 2013

Mechanical properties of ferrochrome based hardfacing layers coated on AISI 1020 steel obtained by the aid of Plasma Transfer Arc (PTA) was experimentally studied. Ferrochrome powders were mixed with sodium silicate gel to avoid spreading. The mixture was laid to 1.5 × 8 × 100 mm slots machined on AISI 1020 steel. Hardfacing layer was performed by PTA process under pure Argon as protective gas with 130 A/20 V power supply. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), micro hardness and abrasive tests were employed for the evaluation of ferrochrome alloyed coating. Hardfacing was successfully performed under given conditions. Microstructural changes and formations (phases) significantly improved hardness, abrasive wear resistance and integrity of hardfacing layer.
Embrittlement of 1.25 Ni-Cr Case Hardenable Steel Used for Gear Assembly
Authors: Jha Abhay K. , Sreekumar K.
Published: December 2013

1.25 Ni-1.0Cr-0.1Mo case hardenable steel of EN353 grade is used for manufacturing gears. One such gear assembly was used in the azimuth control gearbox of an antenna system. After about six months in operation, the gear failed with a big noise in the gearbox during operation. The gearbox when opened showed disintegrated teeth of both gear and pinion, which was found, crushed and resulted in multiple smaller pieces. Globular shaped metallic pieces were also found in the gearbox.

Detailed metallurgical investigation indicated that the fracture of the gear teeth occurred under impact of extraneous globular shaped metallic pieces of plain carbon steel entrapped in the gearbox. Inter-granular mode of fracture developed could be attributed to embrittlement of material.
Microstructural Features of AZ31 Deformed at High Temperatures
Authors: Poletti C. , Warchomicka F. , Okruch R. , Knoblich H.
Published: December 2013

An as-cast AZ31 magnesium alloy was investigated using light microscopy (LOM) and electron backscatter diffraction (EBSD) methods to quantify and describe the deformation mechanisms activated at high temperatures. Compression tests were carried out by means of a Gleeble®1500 device in the range of 320–500°C and 0.03–10 s-1 of strain rate. Deformed samples were simulated by finite elements method to correlate the microstructure with the local deformation parameters. EBSD measurements were used to distinguish and quantify the new recrystallized grains and to characterize the misorientation distribution. These results helped to determine the grain size distribution with the temperature and the strain rate by LOM pictures. Dynamic recrystallization is denoted by necklace microstructure, and twinning promotes the recrystallization nucleation. At high temperature and slow strain rate recovery takes place followed by continuous dynamic recrystallization.
Influence of Welding Speed on Microstructure and Mechanical Properties of AZ31 Magnesium Alloy Laser Weldments
Authors: Babu N. Kishore , Ashfaq M.
Published: December 2013

CO2 laser welds were prepared on 3 mm thick sheets of continuous cast and rolled AZ31 magnesium alloy, using different welding speeds (3 m/min, 4 m/min and 5 m/min). The microstructure and composition analysis of weld metal was examined using optical and scanning electron microscopy (HR-SEM, EPMA and EDS/X). Room temperature hardness and tensile properties of the weldments in the as-welded condition were studied and correlated with the microstructure. The microstructure of fusion zone consists of two parts: the equiaxed zone in the middle part and the columnar zone adjacent to fusion boundary. It has been shown that the average width of columnar grains in the fusion zone is increased with decreasing the welding speed. Microstructural examination showed that the equiaxed grain size in the fusion zone was the least in the welds made using 5 m/min welding speed. It has been shown that welds prepared with 5 m/min welding speed exhibited increase in hardness, yield strength and ductility when compared with other welds.
Grain Size Distributions in Normal Grain Growth
Authors: Zöllner Dana , Streitenberger Peter
Published: December 2013

An analytical distribution function characterising the grain sizes of polycrystalline microstructures is presented. Contrary to standard mathematical probability functions that are still often used for description of experimentally obtained size distributions, this one is based on a statistical mean-field theory of grain growth and is fully consistent with the fundamental physical conditions of total-volume conservation and the existence of a finite average grain volume. It is found that this distribution function describes the grain size distribution obtained by Monte Carlo Potts model simulations better than standard mathematical distributions. Additionally, two-dimensional plane sections from the simulated three-dimensional grain structures are considered and compared with experimental data, and the analytic size distribution function is also compared with an experimental grain size distribution for pure iron obtained by serial sectioning.
Lichtmikroskopische Auswertung der Wirksamkeit thermoplastischer Elastomere als Verarbeitungshilfsmittel in der Blasfolienextrusion von PE-LLD
Authors: Müller Marco , Wagner Manfred H.
Published: December 2013

Kurzfassung

Der vorliegende Beitrag ist dem wissenschaftlichen Wirken von Herrn Dr.-Ing. Jörg Trempler gewidmet und ist gleichzeitig verbunden mit persönlichem Dank, den einer der Autoren für die eigene erhaltene Ausbildung an dieser Stelle ausdrücken möchte. Dieser Artikel diskutiert die Eignung thermoplastischer Elastomere als Kunststoffverarbeitungshilfsmittel in der Blasfolienextrusion von PE-LLD zur Verschiebung von Schmelzflussinstabilitäten in Richtung höherer Verarbeitungsgeschwindigkeit. Ziel ist es, Oberflächendefekte wie den sog. Sharkskin-Effekt zu verzögern, so dass höhere Verarbeitungsgeschwindigkeiten und damit eine höhere Produktivität erreicht werden können. Als Additive kommen verschiedene thermoplastische Elastomere sowohl auf Silicon- als auch auf Urethanbasis zum Einsatz.

Neben der lichtmikroskopischen Auswertung der Folienprodukte wird die Veränderung des rheologischen Verhaltens der Kunststoffschmelze durch die Additive anhand rheometrischer Verfahren (z. B. Kapillarrheometrie) untersucht. In diesem Zusammenhang kommt auch die Methode nach Mooney zur Bestimmung des Gleitanteils beim Durchströmen einer Kunststoffschmelze durch eine Düse zum Einsatz.
Chromium Grain-Boundary Segregation and Effect of Ion Beam Cleaning on Ni-Fe-Cr Alloys
Authors: Saraf L.V.
Published: December 2013

The grain boundaries play important role to control the mechanical strength of ternary alloys. From spacecrafts to naval vessels to nuclear reactors, stress corrosion cracking, brittleness, oxidation mostly originates at the grain boundaries and cause long term structural stability problems in most of the metallic structures [1]. Ni-Fe-Cr based ternary metal alloys have been widely studied for more than fifty years [2, 3]. Despite of vast amount of research, chromium diffusion in stainless steel or other Ni-Fe-Cr based ternary alloys is still an open scientific problem with challenges in structural stability and corrosion resistance [4]. Particularly, austenite Ni-Fe-Cr is looked upon favorably in space and jet engine industry for their improved resistance to stress corrosion cracking [5]. In solid oxide fuel cells (SOFC), Ni-alloys are frequently used as interconnects and seals [6]. In this communication, simultaneous energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) mapping is utilized to study chemical and structural aspects of chromium segregation in Ni-Fe-Cr alloy. A focused Ga-ion beam is also utilized to study the effect of ion beam cleaning on EBSD image quality (IQ) and inverse pole figure (IPF) maps of Ni-Fe-Cr alloy
Metallographische Probenpräparation von verlöteten Solarzellen
Authors: Eberlein Dirk , Schmitt Peter , Voos Patrick
Published: December 2013

Kurzfassung

Die Photovoltaik ist ein junger Industriezweig der stark wachsend auf innovative Technologien setzt. Nicht nur die Verbesserung der Solarzellwirkungsgrade, sondern auch der Einsatz neuer Modultechnologien ist von großer Bedeutung. Das Verschalten von mehreren Solarzellen wird standardmäßig via Weichlöten durchgeführt. Die vorliegende Arbeit stellt ein Verfahren dar, mit welchem die Qualität dieser Lötstellen auf Solarzellen untersucht werden kann. Dies stellt ein gutes Werkzeug in der Forschung und Entwicklung neuer Kontaktierungstechnologien, sowie in der Qualitätssicherung dar.
γ↔∊ Transformation Behavior of Austenitic-Martensitic FeMn(Cr) Steels
Authors: Weiß A. , Tranta F. , Scheller P.R. , Kovalev A.
Published: December 2013

Three differently alloyed austenitic FeMn(Cr) steels have been examined with a focus on the occurrence of ∊ martensite. Studies primarily focus on the detection of ∊ martensite by means of metallographic and X-ray methods as well as by means of dilatometric and DSC measurements. Dilatometric and DSC measurements have also been carried out to determine ∊ martensite formation and dissolution temperatures. Examination results including thermodynamic calculations serve to characterize the formation and dissolution of ∊ martensite in FeMn(Cr) steels.
The Characterisation of a Powder Metallurgically Manufactured TNM™ Titanium Aluminide Alloy Using Complimentary Quantitative Methods
Authors: Schloffer M. , Schmoelzer T. , Mayer S. , Schwaighofer E. , Hawranek G. , Schimansky F.-P. , Pyczak F. , Clemens H.
Published: December 2013

In order to be able to use intermetallic titanium aluminide in industrial applications, a quick and affordable method of quantitatively analysing their microstructures is required. In the presented work it was able to demonstrate on a powder metallurgical manufactured TNM™ alloy of nominal composition Ti-43.5Al-4Nb-1Mo-0.1B (at.%), that by electrolytic-polishing and colour etching a quick and cost effective quantitative microstructural analysis may be carried out via light-optical microscopic images. In doing so, the phase fractions and microstructural constituents of the various types of microstructures present are determined using complementary analysing techniques. Both light-optical and scanning electron microscopic images were captured from each of three different types of microstructures. These were then quantitatively evaluated using an image analysis program. The results were compared with those obtained from X-ray diffraction experiments. The possibilities and limits of the quantitative phase evaluation of light-optical microscopic images of colour etched microstructures are also explained and their relationship to the choice of parameters used for the colour etching and electro-polishing operations discussed.
Dynamic Recovery and Recrystallization during Hot-Working in an Advanced TiAl Alloy
Authors: Schmoelzer T. , Liss K.-D. , Rester M. , Yan K. , Stark A. , Reid M. , Peel M. , Clemens H.
Published: December 2013

Intermetallic TiAl alloys are light-weight high-temperature materials and intended to partly replace Ni based alloys in jet engines. Due to difficult forming operations, component prices are high and limit the possible field of application. During hot-working, recovery and recrystallization effects determine the microstructural evolution and thereby the mechanical properties of the finished part as well as its behavior during deformation. To study the occurring phenomena, in-situ diffraction experiments with high-energy X-rays were conducted. By means of this method, the dominating processes were identified. The results were validated through electron back scatter diffraction experiments.
Microstructure and EPR Studies of 13% Chromium Steels after Various Heat Treatments and the Influence of MnS on the EPR Test
Authors: Strobl S. , Haubner R. , Linhardt P.
Published: December 2013

Current collector rings (X12Cr13 stainless steel, Mat. No. 1.4006) exhibited different susceptibilities for staining, if provided from different manufacturers. The electrochemical potentiokinetic reactivation test (EPR test) revealed sensitisation as the reason for the insufficient corrosion behaviour. In the initial state, steel SS-1 shows a tempered structure and some ferrite with a sensitisation of max. 2.7%; steel SS-2 with a ferritic structure and carbides at the grain boundaries contains MnS and Ti(C,N) and exhibits sensitisation of ≈80%. After establishing a defined starting condition for both steels by solution annealing at 1050°C for 30 min, the steels were hardened in oil, air or cooled slowly in the furnace. Moreover, such oil-quenched samples were annealed at various conditions (800 or 750°C for 45 or 24 h), and the influence on sensitisation was determined via EPR test. The oil-quenched samples revealed the lowest degrees of sensitisation. Some unusual EPR results for SS-2 could be correlated with the dissolution of MnS during the test.
The Materialographic Preparation and Microstructure Characterization of Lithium Ion Accumulators
Authors: Hafner C. , Bernthaler T. , Knoblauch V. , Schneider G.
Published: December 2013

Lithium ion accumulators are widely used already in numerous electronic devices. However, a great deal of research will still be required as to their use as a reliable and efficient energy storage unit in the automotive industry. Their characterization using physical and electrochemical methods has made great progress and was published already. In contrast, the classical materialographic characterization of their microstructure by means of microscopy is applied only to a small extent nowadays. Access by the public to relevant results is scarcely possible.

Properties like capacity and power as well as safety und stability also depend very much on the cell design (e. g. geometry, layer thicknesses) and microstructure (e. g. volume fraction, grain size) of the materials employed. A microstructure analysis by microscopy is intended to provide for a more profound comprehension of the connection between the basic parameters and function here. A challenge is posed by the preparation of a microsection to reveal a representative image of the microstructure without artefacts. The process of materialographic preparation and the potential of various microscopy techniques for visualizing and quantifying the cell components and ageing effects are presented here. The opportunities of characterizing the basic parameters specific to the cells furnishes new knowledge on the properties of battery materials and, hence, will be of great utility for future examinations and further developments of the lithium ion technology.
The Phase and Microstructural Analysis of Protective Oxide Coatings on Molybdenum
Authors: Traxler H. , Jörg R. , Zabernig M. , Sigl L.S.
Published: December 2013

Due to their high sensitivity to oxygen, the use of refractory metals requires an effective protection against oxidation. In the case of molybdenum this is achieved by using a silicon and boron based coating commercially marketed under the trade name SIBOR®. In the moduction of a SIBOR®-coating, a mixture of Si, B and C is plasma sprayed in air onto the Mo-surface to be protected and subsequently annealed in hydrogen. Previous investigations have shown that in doing so a stationary coating of Mo-borides and Mo-silicides is formed. However, the exact phase arrangement and composition has until now remained unclear.

Energy dispersive X-ray spectroscopy (EDS) in the scanning electron microscope (SEM) is able to analyse the silicides in SIBOR®, although due to the overlapping of the Mo- and B-spectral partial a clear identification of the borides was not possible. Using a combination of electron back scatter diffraction (EBSD) and wavelength dispersive X-ray spectroscopy (WDS) it is, however, shown that SIBOR® is made up of a series of sub-layers of Mo2B and MoB followed by Mo5Si3 and MoSi2, and that the other phases of the Mo-Si-B ternary system, i.e. Mo3Si and Mo5SiB2(T2), do not occur.

Notably, the two borides and the Mo5Si3 exhibit a structure which is polycrystalline in the lateral direction yet normal to the surface forms of only a single layer of crystallites. In contrast, the final MoSi2-layer has a polycrystalline structure both in the lateral and in the normal directions. Furthermore, Mo5Si3 and MoSi2 both exhibit marked textures.
Investigations on High Temperature MgB2 Superconductor Wires and Tapes with New Sheath Materials and the Correlation of Their Microstructures and Properties
Authors: Schubert Margitta , Häßler Wolfgang , Rodig Christian , Herrmann Marco , Kario Anna Urszula , Scheiter Juliane , Prescher Heiko , Holzapfel Bernhardt , Schultz Ludwig
Published: December 2013

Long superconducting MgB2 wires and tapes were produced by the “powder in a tube” method (PIT) using a mechanically alloyed nano-powder consisting of Mg, B and MgB2 as the precursor material. Both single-core (SC) and multi-core (MC) conductors were made by swaging and wire drawing the powder contained within a new type of sheath material (ODS-Cu) which, amongst others, also has the advantage of thermally stabilising the conductor.

Metallographic investigations on specimens of the conductors in the as-drawn condition and after heat treatment were carried out both to monitor the manufacturing process as well as to gain information regarding important parameters such as the changes in hardness and ductility of the sheath and filament occurring during the forming process and the effect which they have on the final properties of the conductors. The metallographic and scanning electron microscopic (SEM) investigations of the microstructures were carried out on longitudinal (LS) and cross (XS) sections of the conductors which made it possible to understand the correlation between the microstructures and properties of the conductors and to draw important conclusions in order to be able to achieve the optimum design and best electrical properties for the finished conductors. By heat treating the cold formed conductor in the temperature range 500–650°C, very good superconducting properties were able to be produced with critical temperatures (Tc) of 36 K and critical current densities (jc) of 104 A/cm2 in fields of 11 T (parallel to the tape surface), measured at 4.2 K. Using this new sheath material, a conductor of over 100 m in length was able to be manufactured.
Effect of Austempering Temperature and Time on the Kinetics and Microstructure of Austempered Compacted Graphite Cast Irons
Authors: Teymourian M. , Boutorabi S.M.A.
Published: December 2013

After starting the austempering nucleation of bainitic ferrite was observed within a very short time. Samples that austempered for 2 min.showed martensite in the microstructure. By increasing the austempering time from 30 min to 90 min the retained austenite decomposes and X-ray diffraction observations revealed the greatest volume fraction of retained austenite up to 17.3 and 23.8 percent when austempered for 30 min. Micro-hardness of the bainitic ferrite increased up to 370 and 500 HV and micro-hardness of the retained austenite increased up to 300 and 400 HV at the austempering temperatures of 300°C and 400°C respectively. In comparison to austempered ductile iron, the austempered compacted graphite cast iron shows higher rate of bainitic reaction. Bainite formation driving force and consequently the rate of austempering process are higher in compacted graphite cast irons.
Vibratory Polishing of a Nickel-Based Superalloy (MAR 247) Using VibroMet 2
Authors: Watermeyer P.
Published: December 2013

Preparation artifacts such as scratches, surface deformation and smearing are often difficult to remove by conventional grinding and polishing.

Vibratory polishing is a mechanical process. It provides a very gentle polishing treatment. This final preparation step provides for a removal of ground specimen surfaces without causing deformations. The sample surface was examined on the basis of different mechanical and chemical/mechanical preparation steps with regard to its suitability for subsequent examinations using a scanning electron microscope (for example EBSD measurements).
Examination of the Microstructure and Properties of Low-Frequency Electromagnetic Casting 6060 Aluminum Alloy Billets and Bars
Authors: Markovic S. , Stakic M. , Manasijevic S. , Kamberovic Z. , Radisa R. , Korac M.
Published: December 2013

This study investigated the advantages of using low-frequency electromagnetic casting (LFEC) process compared to conventional direct chill DC casting of aluminum alloy and considered possible energy savings. The obtained results have indicated that casting in low-frequency electromagnetic field offers a series of advantages regarding the quality of aluminum billet, such as smooth billet surface, uniform grain size on the cross section, finer macrostructure and balanced distribution of intermetallic phases in the alloy. This guarantees their good properties in further processing, i.e. pressing, drawing, anodizing, plasticization etc. If the material is properly prepared for melting and for the technological process of casting and if primary aluminum is used as the basic raw material, the 6xxx-series billets can be extruded with no or minor prior thermal homogenization. This is a significant argument for using low-frequency electromagnetic casting (LFEC) process, which allows for significant savings in energy and labor and simplifies the manufacturing process as well.
Preparation and Etching Methods for a Light-Optical Microscopy Analysis of Extrusion Seams and Microstructural Contrasting for Aluminum Alloys EN AW-6063 and EN AW-6082
Authors: Reeb A. , Ohl A. , Poser K. , Kloppenborg T. , Brosius A. , Tekkaya A.E. , Weidenmann K.A.
Published: December 2013

To begin with, a visualization of the seam location as well as of the microstructure of the entire profile cross-section is necessary in order to evaluate the stability of extrusion processes and the resulting relationships between process, microstructure, and properties of extrusion profiles characterized by an extrusion seam. The investigations aim at determining appropriate preparation and etching methods for a light-optical microscope analysis of the longitudinal as well as the transversal extrusion seam in the alloys EN AW-6063 and EN AW-6082 and – in the best case – a simultaneous microstructural contrasting. For this purpose, different chemical etching techniques have been applied. A reliable uncovering of the seam was possible for both alloys using a HF solution. Etching with Weck's reagent after NaOH pre-etching turned out to be a promising method for microstructural contrasting of the EN AW-6063 alloy. The transversal extrusion seam could not be rendered visible by means of conventional etching methods. In this context, extrusion of both alloys (EN AW-6082 and EN AW-6063) applying the billet-to-billet extrusion method in line with visioplastic analyses allowed for an indirect representation of the extrusion seam.
Microstructural Investigation of Melt-Spun NiTi Based Ribbons
Authors: Mehrabi K. , Bruncko M. , Kneissl A.C.
Published: December 2013

In order to get small-dimensioned shape memory alloys (SMAs) with good functional and mechanical properties, a rapid solidification technique was employed. This paper discusses the use of different melt-spinning procedures for the preparation of proper thin NiTi ribbons.

Metallographic characterization of SMAs is an important way to evaluate material properties, therefore the effect of alloy composition and different conditions of melt-spinning process (crucible, melting time and temperature) on the various inclusions and microstructure of NiTi alloys was investigated. Specimens for metallographic studies were cut from the longitudinal cross sections of melt-spun ribbons. The microstructures and different phases were examined by optical, scanning and transmission electron microscopy and the influence of the processing methods on microstructures of ribbons will be discussed.
The Joint Application of Various Microscopy Techniques for the Evaluation of Area Fraction of Structural Components – Theoretical Assumptions and Practical Aspects
Authors: Richter J.
Published: December 2013

The paper discusses employing a variety of microscopical techniques and their limitations in the context of the evaluation of the area fraction of structural components. The idea of the joint application of several types of microscopes to area fraction assessment depending on the sizes of objects being evaluated is introduced. The relevant measuring schemes and formulae for the correct calculation of the total area fraction in two, three, four or five stage analyses using light and electron microscope techniques are presented together with practical examples and results. In this joint approach the advantages of each microscope type are utilized while avoiding the drawbacks. A concept of the local area fraction is suggested and applied in the quantitative evaluation of a carbide phase in an economical niobium high-speed steel. The appropriate variants of the joint method are recommended for various size scales and size distributions of objects to be analyzed. The methods described enable an accurate evaluation of area fraction in cases where the possibilities of single microscope techniques are insufficient.
Structural Changes in Cobalt Solid-Solution Crystals Due to Milling
Authors: Podlesak H. , Gläser C. , Wielage B. , Hösel D. , Neugebauer R.
Published: December 2013

A detailed microstructural study was carried out using a field emission-scanning electron microscope with the aim of analysing the effect of surface work-hardening which occurs when milling the cobalt based hard facing alloy ”Stellite 12“. The strengthening was determined to be caused by the formation of two-dimensional structural defects in the cobalt solid-solution matrix. The assumption that a stress induced martensitic transformation of the crystalline areas of the cubic cobalt phase into thin hexagonal cobalt platelets occurs was confirmed by X-ray diffraction phase analysis. In addition, it was assumed that stacking faults would be formed. For the microscopic investigation, the channeling effect achieved by imaging using a conventional ring-shaped back scattered electron detector proved most useful. Because of needed high quality of polished sections, an optimised method of preparation was developed.
Metallographic Analysis of the Dead Metal Zone In Metal Cutting With a Rounded-Edge Tool
Authors: Öztürk S. , Uysal A. , Altan E.
Published: December 2013

The experimental results show that a small dead region is seen in front of the rake face during cutting with a rounded-edge cutting tool. Although this fact was accepted, metallographic analysis of the dead metal zone had never been conducted. A quick stop device was used to obtain chip root samples that are representative of the deformation taking place during dynamic (actual) cutting conditions. A metallographic analysis was performed on selected specimens to identify the microstructure and formation. The photomicrographs were analyzed and an effort made to explain the dead metal zone microstructure.
Quantitative Analysis of Microstructure in Low Carbon Steel after Thermomechanical Process in (α+γ) Region
Authors: Kolan C. , Wrońska A. , Lis A. , Golański G.
Published: December 2013

This paper presents results of quantitative analysis of ferrite grains in low carbon steel C15V with microalloying addition of vanadium. Thermomechanical treatment in the intercritical (α+γ) region was performed using the dilatometer DIL805A. On the basis of dilatometric researches the critical temperatures of α ↔ γ transformation for C15V steel during heating with v5−8=0.5 K/s and cooling with v8−5=1 K/s were estimated. The steel deformation was carried out with application of two different variants: deformation in (α+γ) region after cooling from full austenitization temperature and deformation in (α+γ) region after heating from ambient temperature (ferritic-bainitic microstructure). The effects of these treatments were observed by means of a light optical microscope in bright and polarized field.

The quantitative analysis of microstructure was investigated using Image Pro Plus (IPP) program. Characteristic parameters for ferrite grains such as: field area, average diameter, shape factor were estimated. For each of these parameters, histograms and maps of average grain diameter distribution were performed using STATISTICA 9 and IPP programs. It was observed that deformation in the intercritical range (α+γ) promotes the occurrence of many ferrite nucleus in the obtained structures, especially at grain boundaries. For low carbon steel this results in formation of very fine microstructure.
Evaluation of Porosity of Precision Castings Made of High-Temperature Creep Resisting Nickel Superalloys
Authors: Roskosz S.
Published: December 2013

The subject matter of the paper is the quantitative evaluation of gaseous and shrinkage porosity in construction elements of a low-pressure aircraft engine turbine using quantitative metallography methods. The research material consisted of blades and blade segments with a polycrystalline structure made of IN 713C and MAR M247 superalloys.

One of the major problems that occur in the precision castings is their porosity: gaseous, which is the result of emission of dissolved gases from the superalloy during solidification, and shrinkage, being the result of shrinkage of the superalloy and from a lack of feeding of the interdendritic space.

The comprehensive procedure of porosity evaluation includes: an automatic decimal-to-binary conversion of pores, a selective quantitative evaluation of gaseous and shrinkage porosity, the development of measuring conditions of quantitative metallography parameters, and the application of structural maps showing the varied porosity distribution over the cross-sections of castings of blades and blade segments.

The developed practical procedure of selective measurement of gaseous and shrinkage porosity in the examination of precision castings made of high-temperature creep resisting nickel superalloys is presented.
Effect of Growth Velocity on Solute Distribution and Electrical Conductivity in a Directionally Solidified Cu–8 %Ag Alloy
Authors: Lee W.-H. , Kang B.-H. , Kim K.-Y. , Cho H.
Published: December 2013

A Cu–8 %Ag alloy was directionally solidified at different growth velocities to investigate the relationship between the solute distribution and the electrical conductivity of the material. The temperature gradient was fixed at 6.1 K/mm, and the growth rate was varied from 1 µ m/s to 200 µ m/s The planar interface was not observed in this experimental range, although cellular and dendritic interface morphologies were observed. As the growth velocity was increased, the initial silver content decreased, while the silver content near the dendrite boundary increased. The lattice parameter of the Cu – Ag alloy increased with increases in the number of silver sites in the copper lattice as measured via a calculation using the VASP (Vienna Ab-initio Package Simulation) code. The lattice parameter also decreased with increases in the growth velocity due to the decrease in silver content in the matrix. Higher electrical conductivity was obtained with higher growth velocities.