Emissionsmikroskopische Untersuchungen zur plastischen Verformung und Versetzungsmarkierung an NbFe2

By means of a homogenous compression device the Laves phase NbFe₂ was deformed plastically while being observed in an emission electron microscope. In connection with these experiments the possibility of marking dislocations was investigated emerging from the crystal by means of a thermal treatment under vacuum conditions in the emission electron microscope. Slip traces on the surfaces were observed only above a critical temperature (transition brittle-ductile). During a high temperature treatment under vacuum oxide nuclei grow on the surface. These nuclei seem to decorate dislocations emerging from the crystal. On surfaces of plastic deformed samples the oxide nuclei mark slip traces.     

Zur plastischen Verformung von Antimoneinkristallen im Druckversuch bei Raumtemperatur

The plastic deformation of antimony single crystals dynamically tested in compression at room temperature has been investigated. As macroscopic deformation mechanisms twinning, dislocation slip, and kinking have been observed. The critical resolved shear stress for basal slip and twinning was measured and the orientation dependence of the deformation mode was explained. It is shown that basal slip dominates compared to rhombohedral slip.     

Elektronenmikroskopische Untersuchungen zur Rißausbreitung bei der Zugverformung gewalzter Molybdän-Einkristalle

The effect of dislocation structure on mechanical properties, crack propagation and fracture was investigated in molybdenum single crystals predeformed by rolling to produce a homogeneously distributed dislocation structure or a cell structure. The rolled crystals were notched and deformed by tension at various temperatures (493, 293 and 193 K). It is shown, that the crystals with cell structure ((111) [112 ] orientation) have the higher strength, but the crystals with homogeneous structure ((001) [110] orientation) are more ductile. In cell structure cracks propagate catastrophically without pronounced necking. The homogeneous structure becomes unstable during tensile loading above the transition temperature, but crack propagation occurs slowly involving complete necking of the crystal. At low temperatures (193 K) cleavage fracture on {100} planes takes place both in the crystals with homogeneous and cell structure.     

Untersuchungen zur Stabilität verschiedener Methoden der tiegelfreien Zonenziehtechnik bei Silizium

This paper reflects on stability of two floating zone techniques, the downward zoned pedestal technique or upward zoned pedestal technique for silicon. It can be shown that stable conditions are only possible in upward zoned techniques.     

Änderung von Verformungseigenschaften der intermetallischen Verbindung MgZn2 im Homogenitätsbereich

Solid solution softening within the range of homogeneity of the intermetallic compound MgZn₂ appears to be due to variations of the dislocation density. This has been shown by independent measurements of dislocation velocity and dislocation density.     

Die Änderung der Molekül- und Kristallstruktur des N-Methyl-piperidinum-acet-meta-chlor-anilid-jodid durch Einlagerung von Wasser

N-Methyl-piperidinium-acet-meta-chloro-anilide-iodide crystallizes from water in the space group Pna2₁ with 4 formula units C₁₄H₂₀N₂OClJ and 4 H₂O molecules in the unit cell. The lattice constants are a = 12.413 Å, b = 19.798 Å and c = 6.919 Å. The change of the molecular conformation caused by water molecules was investigated by X-ray structure analysis.     

Untersuchungen zur Neubildung von Versetzungen bei der tiegelfreien Züchtung von Silizium-Einkristallen

During the crucible free growing of dislocation free silicon monocrystals frequently spontaneous generations of new dislocations are observed which cannot be attributed to perceptible reasons. By means of X-ray topographic and metallographic methods it is tried to localize the origin of these dislocation generations in the crystal. Their generation in areas of the crystal surface permits to suppose the existence of a temperature stress mechanism, which releases the generation of new dislocations in the plastic regions of the just formed crystal in consequence of high shocks of stress.     

Erholung und Rekristallisation des stabilen Austenits bei der Verformung durch Walzen

For the explanation of the processes which take place during a high-temperature thermomechanical treatment (HTTT) in the stable austenite hardness, grain structure and dislocation structure of a Fe 24Ni 0,5C alloy are examined in dependence of the degree and temperature of rolling deformation (ϵ = 13 to 52%; T_v = 830 and 1150°C). The observed structures can be represented by a recovery-recrystallization-diagram, that describes the influence of technological parameters on the recovery and the recrystallization of stable austenite.     

Beiträge zum Ätzen von Galliumarsenid (I) Strukturtheoretische Diskussion der erzeugten Ätzmorphologien

{111}-, {110}- and {100}-plates of GaAs have been etched in various etching solutions followed by comparing the obtained etching structures. The fundamentals of the discussion is the existing correlation between the morphology of etch pits and crystal structure. It is shown that a qualitative interpretation of the manifold etching phenomena on the above faces in a structure characteristic for GaAs can be given by including 1. the presence of primary defects as a constitutive property of real crystals and 2. the consideration of recordable influences of the surroundings.     

Die Anwendung des Quantimet zur Ätzgrubendichtebestimmung an Silizium-Einkristallen

A quantitative estimation of the structure of etched silicon crystals is possible with the microscope Quantimet by a fast counting the number of particles, i.e. etch pits on {111}-planes. Boundary conditions of the measuring technique are the requisite size of the etch pits of from > 3 … 5 μm, a plane specimen surface, the correct optical magnification, threshold and acceptance width. Sources of errors due to the structure result from the overlap of etch pits at dislocation densities > 10⁴ cm⁻² which leads to an underestimation of the number of etch pits because of the reduced signal output. An overestimation is most caused by an unwished contrast in the surface which yields additional signal outputs. The errors will be eliminated by using a calibration curved. Due to the short time which is necessary for counting, the Quantimet is well suitable for routine testings and for quantitative evaluation of the structure defects (etch pit density) in silicon, including consideration of possible errors.     

Gleitbanduntersuchungen während und nach Verformung der intermetallischen Verbindung MgZn2

Measurements of densities, lengths, offsets and velocities of slip bands have been performed by optical microscopy of surfaces of the single crystalline intermetallic compound MgZn₂ plastically deformed at temperatures from 245 to 427°C. From their shear strain dependence conclusions have been drawn concerning the behaviour of dislocations during deformation of this compound completely brittle at room temperature.     

Elektronenmikroskopische Untersuchungen zur Oxidkeimbildung an Reineisenoberflächen

During a high temperature treatment of pure α-iron crystals under vacuum conditions (po₂ = 1 · 10⁻⁴ … 1 · 10⁻⁶ torr) single oxide nuclei originate on the crystal surfaces. The oxide was identified as γ-Fe₂O₃. From the definite shape of the nuclei on (100) oriented α-iron and from their orientations relative to the iron lattice an epitaxial growth may be concluded, following the well-known relation (100)_Fe ∥ (100)_Oxide; [100]_Fe ∥ [110]_oxide. Grown-in dislocations, surface steps and grain boundaries of the matrix were decorated by the oxide nuclei. However, oxide nuclei did not originate at the emergent points of fresh dislocations.     

Beitrag zur Kenntnis der Beziehungen zwischen Aktivierungsmechanismus und Strukturänderungen in Festkörpern Untersuchungen zur Verteilung amorpher Bereiche auf schwinggemahlenen Quarzoberflächen

The thickness of the X-ray amorphous layers are estimated and compared with the data from literature. – The mean thickness of the layers is 10–30 nm and almost independent on the degree of amorphization and the specific surface.     

Ätzuntersuchungen an Verneuilspinellen

The quality of (100), (110), and (111) oriented spinel substrates in the composition range MgO × 3.3-3.5 Al₂O₃ is examined by chemical etching. The investigation shows that KHSO₄, H₃PO₄, and Na₂B₄O₇ cause dislocation etch pits on (111), and only KHSO₄ on (100) faces. The little rod-shaped defects revealed by etching on (100), (110), and (111) faces were found to be Al₂O₃ precipitates.