Large-scale volcanic deformation recently detected by radar interferometry (InSAR) provides new information and thus new scientific challenges for understanding volcano-tectonic activity and magmatic systems. The destabilization of such a system at depth noticeably affects the surrounding environment through magma injection, ground displacement and volcanic eruptions. To determine the spatiotemporal evolution of the Lazufre volcanic area located in the central Andes, we combined short-term ground displacement acquired by InSAR with long-term geological observations. Ground displacement was first detected using InSAR in 1997. By 2008, this displacement affected 1800 km2 of the surface, an area comparable in size to the deformation observed at caldera systems. The original displacement was followed in 2000 by a second, small-scale, neighbouring deformation located on the Lastarria volcano. We performed a detailed analysis of the volcanic structures at Lazufre and found relationships with the volcano deformations observed with InSAR. We infer that these observations are both likely to be the surface expression of a long-lived magmatic system evolving at depth. It is not yet clear whether Lazufre may trigger larger unrest or volcanic eruptions; however, the second deformation detected at Lastarria and the clear increase of the large-scale deformation rate make this an area of particular interest for closer continuous monitoring. / Vulkanische Deformationen in großem Maßstab, die mittels InSAR gemessen wurden, liefern neue Informationen und dadurch einen neuen Blickwinkel auf vulkan-tektonische Aktivitäten und das Verständnis von langlebigen, magmatischen Systemen. Die Destabilisierung eines solchen Systems in der Tiefe beeinflusst dauerhaft die Oberfläche durch Versatz des Bodens, magmatische Einflüsse und vulkanische Unruhen. Mit der Kombination aus kleinräumigem Bodenversatz gemessen mittels InSAR, numerischer Modellierung und langfristigen geologischen Beobachtungen, analysieren wir die Gegend um den Vulkan Lazufre in den Zentralanden, um die raumzeitliche Entwicklung der Region zu bestimmen. Bodenversatz wurde hierbei im Jahr 1997 mittels Radar-Interferrometrie (InSAR) gemessen, was eine Fläche von 1800 km² ausmacht, vergleichbar mit der Größe der Deformation des Kraters. Im Jahr 2000 wurde zusätzlich eine kleinräumige Deformation am Nachbarvulkan Lastarria entdeckt. Wir sehen räumliche als auch zeitliche Verbindungen zwischen der Deformation des Vulkans und vulkanischen Strukturen innerhalb der betroffenen Gegend. Wir folgern daraus, dass diese Beobachtungen der Ausdruck eines langlebigen, magmatischen Systems in der Tiefe an der Oberfläche sind. Es ist noch nicht klar, ob Lazufre größere vulkanische Unruhen, wie zum Beispiel Eruptionen auslösen könnte, aber die Deformation am Vulkan Lastarria und ein Anstieg der großräumigen Deformationsrate, machen diese Region interessant für eine zukünftige, kontinuierliche Überwachung.

Metallic glasses are amorphous alloys that do not possess long-range structural order in contrast to crystalline alloys. Ni-free Ti-based bulk metallic glasses (BMGs) have potential for biomedical applications due to their attractive properties such as high strength, good corrosion resistance and excellent micro-formability, which cannot be obtained for conventional crystalline alloys. In this PhD thesis, Ni-free Ti-based BMGs, i.e. Ti40Zr10Cu34Pd14Sn2 and Ti40Zr10Cu36-xPd14Inx (x = 0, 2, 4, 6, 8), were prepared in the shape of rods by suction casting. Both alloy classes were systematically characterized in terms of glass forming ability, thermal stability, phase formation and mechanical properties. The largest diameter obtained in the fully glassy state for Ti40Zr10Cu34Pd14Sn2 alloy is 3 mm and for Ti40Zr10Cu36-xPd14Inx (x = 2, 4, 6, 8) alloys is 2 mm. Base alloy (Ti40Zr10Cu36Pd14) contains some crystalline phase(s) in the glassy matrix for a 2 mm diameter rod. The structural transformations of Ti40Zr10Cu34Pd14Sn2 BMG upon heating were thoroughly analyzed by utilizing different combination of methods. Firstly, we used differential scanning calorimetry (DSC), X-Ray diffraction (XRD) and transmission electron microscopy (TEM) to investigate the first crystallization event. The main products of the first crystallization are possibly -(Ti, Zr) and Cu3Ti (orthorhombic) phases. Secondly, we employed in situ x-ray diffraction in transmission mode using synchrotron beam to deeply study the thermally-induced structural changes like relaxation, glass transition and crystallization. Since the first peak in the diffraction patterns reflects the structure of the glassy phase on the medium-range scale, the position, width and intensity of this peak in diffraction patterns are fitted through Voigt function below 800 K. All the peak position, width and intensity values show a nearly linear increase with increasing temperature to the onset temperature of structural relaxation, Tr = 510 K. However, these values start to deviate from the linear behavior between Tr and glass transition temperature Tg. The changes in the free volume, which was arrested during rapid quenching of the BMG, and the coefficient of volumetric thermal expansion prove that the aforementioned phenomenon is closely related to the structural relaxation. Above 800 K, three crystallization events are detected and the first exothermic event is due to the formation of metastable nanocrystals. For the Ti40Zr10Cu34Pd14Sn2 alloy, 2 mm diameter rods exhibit the best combination of mechanical properties (e.g. large plastic strain and high yield strength) among all the diameters (ø2, ø3 and ø4 mm) under the room-temperature compression tests. With the aim to improve its room-temperature mechanical properties, the processes of pre-annealing and cold rolling have been applied for the 2 mm diameter rods. Annealed and quenched specimens below Tg and in the supercooled liquid region (between Tg and onset crystallization temperature Tx) do not lead to the enhancement of the plasticity compared to as-cast alloys due to annihilation of excess free volume and crystallization. Cold rolling can effectively improve the plasticity of this BMG by inducing structural heterogeneities. Rolled samples up to a thickness reduction of 15% result in the largest plasticity of 5.7%. Low yield strength and visible work hardening ability are observed in the both 10%-rolled and 15%-rolled samples. The deformation behavior of Ti40Zr10Cu34Pd14Sn2 BMG at the elevated temperatures slightly below Tg and in the supercooled liquid region has been investigated. The stress-strain relations for this BMG over a broad range of temperatures (298 ~716 K) and strain rates (10-5 to 10-3 s-1) were established in uniaxial compression. Under compression tests at the highest test temperature of 716 K, the Ti-based BMG partially crystallizes and low strain rates can lead to the formation of larger volume fractions of crystals. In order to further improve the plasticity of Ti-Zr-Cu-Pd BMGs and simultaneously reduce the content of Cu (considering harmful element for the human body), the Ti40Zr10Cu36-xPd14Inx (x = 2, 4, 6, 8) BMGs have been newly developed with different short- or medium-range order in the structure. The compressive global strain of Ti40Zr10Cu36-xPd14Inx (x = 0, 2, 4, 6, 8) can be significantly improved from 4.5% for the In-free alloy to 10.2% for x = 4. However, a further increase of the indium content to 8 at.% results in a decrease of the plasticity. Among all the monolithic Ni-free Ti-based BMGs reported so far, the novel Ti40Zr10Cu32Pd14In4 BMG shows the largest plasticity. Inspired by the dislocation concept in crystalline materials, we propose a strategy for the design of ductile BMGs through minor substitution using relatively large atoms, which make the bonding nature become more metallic and with it less shear resistant. Such a locally modified structure results in topological heterogeneity, which appears to be crucial for achieving enhanced plasticity. This strategy is verified for Ti-Zr-Cu-Pd glassy alloys, in which Cu was replaced by In, and seems to be extendable to other BMG systems. The atomic-scale heterogeneity in BMGs is somewhat analog to defects in crystalline alloys and helps to improve the overall plasticity of BMGs.

NiAl ist eine intermetallische Verbindung mit kubischer B2-Struktur. Unterhalb der Spröd-duktil-Übergangstemperatur, die bei Normaldruck bei etwa 300°C liegt, können nach dem Von-Mises-Kriterium nicht ausreichend viele unabhängige Gleitsysteme zur homogenen plastischen Verformung aktiviert werden, da die Bruchspannung unterhalb der kritischen Schubspannung zur Aktivierung des sekundären Gleitsystems liegt. Um NiAl trotzdem massiv plastisch verformen zu können, muss die Verformung bei hohem Druck erfolgen. Dies ist beispielsweise möglich bei der Verformung mittels Gleichkanal- Winkelpressen (ECAP) oder Hochdrucktorsion (HPT). Hierbei werden sehr hohe Verformungsgrade erreicht. In dieser Arbeit wird nun die Gefüge- und Texturentwicklung bei Verformung mittels HPT bei Temperaturen zwischen Raumtemperatur und 500°C in Abhängigkeit von Temperatur und hydrostatischem Druck sowie Verformungsgrad untersucht und mit den entsprechenden Größen bei der Verformung mit ECAP verglichen. Es zeigt sich, dass bei der HPT-Verformung die für kubisch-raumzentrierte Metalle typische Schertextur auftritt; zudem findet sich ab einer Verformungstemperatur von 100°C eine geneigte Würfellage, die durch dynamische Rekristallisation entstanden ist und deren Intensität mit der Verformungstemperatur ansteigt. Auch bei den ECAP-Proben findet man die typische Schertextur, eine Würfeltextur tritt nicht auf. Bei beiden Prozessen kommt es zur Kornfeinung, die beeinflusst wird von Verformungstemperatur, Druck und Verformungsgrad. Eine verbesserte Duktilität kann im Zugversuch nicht festgestellt werden, während eine gesteigerte Festigkeit durch Mikro- härtemessungen bestätigt wird. Bei genügend hoher Verformung findet man auch nach der Verformung von Einkristallen eine typische Schertextur. / NiAl is an intermetallic compound with a cubic B2 structure. Below the brittle-to-ductile transition temperature at about 300°C under ambient pressure the number of independent slip systems that have to be activated for a homogeneous plastic deformation is not sufficiently high according to the von Mises criterion. This is because the fracture stress is smaller than the critical yield stress for the activation of the secondary slip system. Despite this, severe plastic deformation is possible under a high pressure. It can be realized by deforming by equal channel angular pressing (ECAP) or high pressure torsion (HPT). Thereby a very high degree of deformation is reached. In this work, texture and microstructure evolution after deformation by HPT at different tem- peratures between room temperature and 500°C and at different hydrostatic pressures and degrees of deformation are analysed and compared to texture and microstructure after ECAP. After deformation by HPT, a texture typical for sheared body-centred metals is found; besides, for a deformation temperature of 100°C and higher an oblique cube component appears. It develops by dynamic recrystallization and grows with increasing deformation temperature. The shear texture also arises in the ECAP deformed samples, but no oblique cube texture is found. Both processes lead to grain refinement, which is influenced by deformation temperature, pressure, and degree of deformation. Tensile testing doesn’t show an enhanced ductility, but an improved strength is confirmed by microhardness measurements. If the degree of deformation is high enough, a shear texture can even be found after deforming single crystals.

Wirtschaftliche und ökologische Rahmenbedingungen zwingen die Forschung immer weiter, die Betriebseigenschaften von Maschinenelementen zu verbessern. Für hydrodynamische Gleitlager wird die Abweichung der zylindrischen Form untersucht, um gezielt Betriebsparameter zu begünstigen. Untersuchungen mit ALP3T dienen der Ermittlung lastfallabhängiger Vorzugsgeometrien. Weiterführende Simulationsuntersuchungen mit Creo Simulate ermöglichen im Anschluss die praxisnahe Formgenerierung. Eine Überführung der Ergebnisse zwischen den beiden Programmen liefert die lastfall- und formabhängigen Betriebsparameter des Gleitlagers. Mit Hilfe der Kopplung können in iterativen Simulationsschritten Fehler reduziert und somit lastfallspezifische Lagergeometrien präsentiert werden. Ferner lässt sich für das Gleitlager ein Demonstrator konzipieren, der diese Lagergeometrien aufbringt.

A ring mesh is a large-scale manufacturable structure with versatile applications in architecture and for protective systems. However, the static and dynamic numerical simulation of a large-scale ring mesh is a resource-intensive task due to the many nonlinear contact points between the individual rings. To characterize the rigid body behavior of the ring mesh, in this paper, a representative volume element is loaded under different in-plane directions. The Green-Lagrangian strain tensor components are obtained as a result. An implicit one-step algorithm is used for this dynamic relaxation issue, modified by the use of stiff springs. Static convergence positions of a representative volume element are determined in several multiaxial tensile directions. The obtained deformation parameters can be used to simulate large deformations of large-scaled ring meshes.

Gelöster Wasserstoff in Metallen führt in vielen Fällen zu einer Reduzierung der Güte von mechanischen Eigenschaften. Dies äußert sich auf vielfältige Weise und wird unter dem Begriff Wasserstoffversprödung zusammengefasst. Für ein grundlegendes Verständnis dieses Phänomens müssen die Vorgänge im Metall auf mikroskopischer Skala ergründet werden. Im Rahmen dieser Arbeit wurde daher ein Aspekt der Wasserstoffversprödung, die Interaktion von Wasserstoff mit Versetzungen, näher untersucht. Zur Untersuchung des Einflusses von Wasserstoff auf die Versetzungsbildung wurden verschiedene Verformungsexperimente an Palladium und Vanadium durchgeführt. Prinzipielle Vorgänge der Defektbildung wurden durch Versuche an einzelnen Versetzungen unter Verwendung von Nanoindentation und Zugexperimenten im ETEM durchgeführt, um einen breiten Überblick zu erlangen. Zusätzlich wurden zum besseren Verständnis der Vorgänge Molekulardynamiksimulationen von derartigen Versuchen ausgeführt. Zur Untersuchung der Interaktion von Versetzungen miteinander wurden Säulen im Mikrometerbereich verformt und Blech durch Kaltwalzen verformt. Des Weiteren wurde durch Hochdruck-Torsion maximale Verformungen realisiert. Die verwendeten Modellmaterialien erlauben es verschiedene prinzipielle Vorgänge der Defektbildung zu untersuchen und so einen breiten Überblick über prinzipielle Vorgänge im kfz Gitter (Palladium) bzw. krz Gitter (Vanadium) zu erhalten.

NiAl ist eine intermetallische Verbindung mit kubischer B2-Struktur. Unterhalb der Spröd-duktil-Übergangstemperatur, die bei Normaldruck bei etwa 300°C liegt, können nach dem Von-Mises-Kriterium nicht ausreichend viele unabhängige Gleitsysteme zur homogenen plastischen Verformung aktiviert werden, da die Bruchspannung unterhalb der kritischen Schubspannung zur Aktivierung des sekundären Gleitsystems liegt. Um NiAl trotzdem massiv plastisch verformen zu können, muss die Verformung bei hohem Druck erfolgen. Dies ist beispielsweise möglich bei der Verformung mittels Gleichkanal- Winkelpressen (ECAP) oder Hochdrucktorsion (HPT). Hierbei werden sehr hohe Verformungsgrade erreicht. In dieser Arbeit wird nun die Gefüge- und Texturentwicklung bei Verformung mittels HPT bei Temperaturen zwischen Raumtemperatur und 500°C in Abhängigkeit von Temperatur und hydrostatischem Druck sowie Verformungsgrad untersucht und mit den entsprechenden Größen bei der Verformung mit ECAP verglichen. Es zeigt sich, dass bei der HPT-Verformung die für kubisch-raumzentrierte Metalle typische Schertextur auftritt; zudem findet sich ab einer Verformungstemperatur von 100°C eine geneigte Würfellage, die durch dynamische Rekristallisation entstanden ist und deren Intensität mit der Verformungstemperatur ansteigt. Auch bei den ECAP-Proben findet man die typische Schertextur, eine Würfeltextur tritt nicht auf. Bei beiden Prozessen kommt es zur Kornfeinung, die beeinflusst wird von Verformungstemperatur, Druck und Verformungsgrad. Eine verbesserte Duktilität kann im Zugversuch nicht festgestellt werden, während eine gesteigerte Festigkeit durch Mikro- härtemessungen bestätigt wird. Bei genügend hoher Verformung findet man auch nach der Verformung von Einkristallen eine typische Schertextur. / NiAl is an intermetallic compound with a cubic B2 structure. Below the brittle-to-ductile transition temperature at about 300°C under ambient pressure the number of independent slip systems that have to be activated for a homogeneous plastic deformation is not sufficiently high according to the von Mises criterion. This is because the fracture stress is smaller than the critical yield stress for the activation of the secondary slip system. Despite this, severe plastic deformation is possible under a high pressure. It can be realized by deforming by equal channel angular pressing (ECAP) or high pressure torsion (HPT). Thereby a very high degree of deformation is reached. In this work, texture and microstructure evolution after deformation by HPT at different tem- peratures between room temperature and 500°C and at different hydrostatic pressures and degrees of deformation are analysed and compared to texture and microstructure after ECAP. After deformation by HPT, a texture typical for sheared body-centred metals is found; besides, for a deformation temperature of 100°C and higher an oblique cube component appears. It develops by dynamic recrystallization and grows with increasing deformation temperature. The shear texture also arises in the ECAP deformed samples, but no oblique cube texture is found. Both processes lead to grain refinement, which is influenced by deformation temperature, pressure, and degree of deformation. Tensile testing doesn’t show an enhanced ductility, but an improved strength is confirmed by microhardness measurements. If the degree of deformation is high enough, a shear texture can even be found after deforming single crystals.

Metallic glasses are amorphous alloys that do not possess long-range structural order in contrast to crystalline alloys. Ni-free Ti-based bulk metallic glasses (BMGs) have potential for biomedical applications due to their attractive properties such as high strength, good corrosion resistance and excellent micro-formability, which cannot be obtained for conventional crystalline alloys. In this PhD thesis, Ni-free Ti-based BMGs, i.e. Ti40Zr10Cu34Pd14Sn2 and Ti40Zr10Cu36-xPd14Inx (x = 0, 2, 4, 6, 8), were prepared in the shape of rods by suction casting. Both alloy classes were systematically characterized in terms of glass forming ability, thermal stability, phase formation and mechanical properties. The largest diameter obtained in the fully glassy state for Ti40Zr10Cu34Pd14Sn2 alloy is 3 mm and for Ti40Zr10Cu36-xPd14Inx (x = 2, 4, 6, 8) alloys is 2 mm. Base alloy (Ti40Zr10Cu36Pd14) contains some crystalline phase(s) in the glassy matrix for a 2 mm diameter rod. The structural transformations of Ti40Zr10Cu34Pd14Sn2 BMG upon heating were thoroughly analyzed by utilizing different combination of methods. Firstly, we used differential scanning calorimetry (DSC), X-Ray diffraction (XRD) and transmission electron microscopy (TEM) to investigate the first crystallization event. The main products of the first crystallization are possibly -(Ti, Zr) and Cu3Ti (orthorhombic) phases. Secondly, we employed in situ x-ray diffraction in transmission mode using synchrotron beam to deeply study the thermally-induced structural changes like relaxation, glass transition and crystallization. Since the first peak in the diffraction patterns reflects the structure of the glassy phase on the medium-range scale, the position, width and intensity of this peak in diffraction patterns are fitted through Voigt function below 800 K. All the peak position, width and intensity values show a nearly linear increase with increasing temperature to the onset temperature of structural relaxation, Tr = 510 K. However, these values start to deviate from the linear behavior between Tr and glass transition temperature Tg. The changes in the free volume, which was arrested during rapid quenching of the BMG, and the coefficient of volumetric thermal expansion prove that the aforementioned phenomenon is closely related to the structural relaxation. Above 800 K, three crystallization events are detected and the first exothermic event is due to the formation of metastable nanocrystals. For the Ti40Zr10Cu34Pd14Sn2 alloy, 2 mm diameter rods exhibit the best combination of mechanical properties (e.g. large plastic strain and high yield strength) among all the diameters (ø2, ø3 and ø4 mm) under the room-temperature compression tests. With the aim to improve its room-temperature mechanical properties, the processes of pre-annealing and cold rolling have been applied for the 2 mm diameter rods. Annealed and quenched specimens below Tg and in the supercooled liquid region (between Tg and onset crystallization temperature Tx) do not lead to the enhancement of the plasticity compared to as-cast alloys due to annihilation of excess free volume and crystallization. Cold rolling can effectively improve the plasticity of this BMG by inducing structural heterogeneities. Rolled samples up to a thickness reduction of 15% result in the largest plasticity of 5.7%. Low yield strength and visible work hardening ability are observed in the both 10%-rolled and 15%-rolled samples. The deformation behavior of Ti40Zr10Cu34Pd14Sn2 BMG at the elevated temperatures slightly below Tg and in the supercooled liquid region has been investigated. The stress-strain relations for this BMG over a broad range of temperatures (298 ~716 K) and strain rates (10-5 to 10-3 s-1) were established in uniaxial compression. Under compression tests at the highest test temperature of 716 K, the Ti-based BMG partially crystallizes and low strain rates can lead to the formation of larger volume fractions of crystals. In order to further improve the plasticity of Ti-Zr-Cu-Pd BMGs and simultaneously reduce the content of Cu (considering harmful element for the human body), the Ti40Zr10Cu36-xPd14Inx (x = 2, 4, 6, 8) BMGs have been newly developed with different short- or medium-range order in the structure. The compressive global strain of Ti40Zr10Cu36-xPd14Inx (x = 0, 2, 4, 6, 8) can be significantly improved from 4.5% for the In-free alloy to 10.2% for x = 4. However, a further increase of the indium content to 8 at.% results in a decrease of the plasticity. Among all the monolithic Ni-free Ti-based BMGs reported so far, the novel Ti40Zr10Cu32Pd14In4 BMG shows the largest plasticity. Inspired by the dislocation concept in crystalline materials, we propose a strategy for the design of ductile BMGs through minor substitution using relatively large atoms, which make the bonding nature become more metallic and with it less shear resistant. Such a locally modified structure results in topological heterogeneity, which appears to be crucial for achieving enhanced plasticity. This strategy is verified for Ti-Zr-Cu-Pd glassy alloys, in which Cu was replaced by In, and seems to be extendable to other BMG systems. The atomic-scale heterogeneity in BMGs is somewhat analog to defects in crystalline alloys and helps to improve the overall plasticity of BMGs.

We consider a microscopic field theoretical approach for interacting active nematic particles. With only steric interactions the self-propulsion strength in such systems can lead to different collective behaviour, e.g. synchronized self-spinning and collective translation. The different behaviour results from the delicate interplay between internal nematic structure, particle shape deformation and particle–particle interaction. For intermediate active strength an asymmetric particle shape emerges and leads to chirality and self-spinning crystals. For larger active strength the shape is symmetric and translational collective motion emerges. Within circular confinements, depending on the packing fraction, the self-spinning regime either stabilizes positional and orientational order or can lead to edge currents and global rotation which destroys the synchronized self-spinning crystalline structure.

No description available.