Plastische Verformung von Kobalteinkristallen

Abstract

Kobalteinkristalle wurden bei mehreren Temperaturen im Zngversuch plastisch verformt. Auch bei tiefen Temperaturen war die Verformbarkeit der Einkristalle sehr gut. Verfestigungskurve und elektronenmikroskopisches Gleitlinienbild gleichen qualitativ denjenigen anderer hexagonaler Metalle und konnen in gleicher Weise gedeutet werden. Neben der Abgleitung auf der Basisebene werden bei den untersuchten Kristallorientierungen 11 122)und {11~4}-Zwillingsebenen beobachtet. Die geometrischen Verhaltiiisse bei dieser sogenannten anomalen Zwillingsbildung werden diskutiert.Kobalt single crystals were plastically deformed in tension at various temperatures. The ductility of the crystals remained good even at lorn temperatures. The work-hardening curves and the elektron microscopy slip line patterns are qualitatively similar to those of other hexagonal metals and may be similarly interpreted. Besides plastic shear on the basal plane, {11%?} and (1134) twin planes are observed for the investigated crystal orientations. The geometry of this so-called anomalous twin formation is discussed.

Modeling analysis of the influence of plasticity on high pressure deformation of hcp-Co

“…5,8 Elastic properties have been obtained under ambient pressure using ultrasonic techniques 38 and at high pressure using inelastic x-ray scattering 19,20,39 ͑IXS͒, Raman spectroscopy, 3 impulsive stimulated light scattering, 23 and first-principles techniques. 5 The plastic properties of hcp-Co have been investigated under ambient pressure for both coarse grains [40][41][42][43][44] and nanocrystalline samples. [45][46][47] High pressure diamondanvil cell ͑DAC͒ radial diffraction ͑RDX͒ experiments have been reported, 22 but lacked an interpretation based on the interplay between elastic and plastic mechanisms.…”

Magnetization and Magnetostriction of Hexagonal Cobalt Single Crystals with Internal Stresses

“…The crystal was grown using the method described by Seeger et al [9]. The angle plo between the c-axis and the cylinder axis was 43' before and 50" after plastic deformation.…”

“…The measurements were carried out on a cylindrical cobalt single crystal (r = 2 mm, 1 = 80 mm) before and after plastic deformation (at room temperature). The crystal was grown using the method described by Seeger et al [9]. The angle plo between the c-axis and the cylinder axis was 43' before and 50" after plastic deformation.…”

“…According t o electron microscope slip-line studies on deformed cobalt single crystals [9] the dislocation density increases linearly with the resolved shear strain. One finds [9] N = 3. 5 x lo8 (0.029 + a) [~m -~] .…”

Quantitative Studies on the Amorphization of Quasicrystals by Means of High Voltage Electron Microscopy

“…This justifies the assumption of a spherical displacement surface (cf. von Jan and Seeger [13]). Additionally, we assume for this displacement surface a step-like functional dependence on the energy, E,,, transferred from the electrons to the (quasi)crystal atoms: an atom, or the created QI, is permanently displaced if E,, exceeds the displacement threshold energy, Ei!, and recombines spontaneously with its QV if E,, is smaller than, or equal to, Ei:.…”