Papers by Author: H.R. Sinning

Abstract: The annealing behaviour of temperature-dependent mechanical spectra (vibrating-reed technique) was studied on electrodeposited ultrafine-grained nickel as well as on Ni nanocomposites with small (7 nm) SiO₂ or larger (25 nm) Al₂O₃ nanoparticles. From the response of the different phenomena involved – Young’s modulus, high-temperature damping background, dislocation-and hydrogen-induced low-temperature loss peaks, and magnetomechanical effects – information is obtained on processes such as recovery, grain growth, hydrogen trapping, and dislocation generation by thermal stresses, which are influenced by both kinds of nanoparticles in different ways.

Abstract: Carbon-containing Fe - Si and Fe - Si - Al alloys were studied with respect to the carbonrelated Snoek-type and Zener relaxation using different mechanical spectroscopy techniques. In all alloys the temperature-dependent profile of the Snoek peak, relative to that in pure iron, is modified on its high-temperature side by the substitutional atoms. At least two components, an Fe - C - Fe (which correspond to C atom jumps (diffusion) in areas where it is surrounded by Fe atoms only) and Fe - C - Me peaks, where Me = Si, Al, can be distinguished in the Snoek-peak profile. In both binary Fe - Al and Fe - Si and ternary Fe - Si - Al alloys, a higher annealing temperature prior to quenching leads to an increase in the Fe - C - Fe and a decrease in the Fe - C - Me component of the Snoek peak. Heating to 1173K and above often lowers the peak height due to thermal vacancies. Low-temperature (<670K) ageing of quenched Fe - Si - Al and Fe – Si specimens reduces both the Fe – C - Fe and Fe – C – Al / Si peaks. Ageing at T > 670 K changes the temperature- as well as the amplitude-dependent parts of internal friction due to a redistribution of carbon between solid solution and dislocations. Both the Snoek-type peak height and the dislocation mobility – as can be concluded from the slope of the amplitude-dependent internal friction – increase, and a new peak appears at temperatures higher than that of the Snoek peak, which probably is a Snoek-Köster peak resulting from the motion of weakly pinned dislocations. A Zener peak appears if the concentration of substitutional atoms is > 6 at. %. The Zener peak relaxation strength is much lower in ternary alloys than in the binary ones probably due to mutual compensation of elastic distortions in presence of Al and Si atoms which are bigger and smaller, respectively, than Fe atoms.

Abstract: Measurements of the H-induced damping peak in Zr-based multi-component metallic glasses, with different tendency to quasicrystal formation, are added to previous reviews of the properties of this damping peak in metallic glasses, and also compared to Ti-Zr-Ni quasicrystals. The results, mainly discussed in terms of a Snoek-type relaxation mechanism for both structure types, indicate a negative correlation between the degree of icosahedral order and the temperature of the damping peak, so that improved damping properties of hydrogen-absorbing bulk metallic glasses can apparently be expected from stronger deviations from icosahedral short-range order.

Abstract: The use of mechanical spectroscopy to characterize the quasicrystalline state of solid matter is reviewed. After a general, chronological survey of existing mechanical spectroscopy studies, which include elastic properties as well as various relaxation phenomena between lowtemperature tunneling processes and high-temperature background damping, three subjects are considered in more detail: (i) the nature of intrinsic relaxation phenomena, including relaxation peaks in Al-Pd-Mn single quasicrystals, (ii) hydrogen-induced loss peaks in Zr/Ti-based quasicrystals and their use as a probe, and (iii) the study of nano-quasicrystalline structures and amorphousquasicrystalline transitions. It is shown that by combined studies of different elastic and anelastic phenomena, mechanical spectroscopy can be a valuable tool to obtain information about the nature and motion of defects, about the type of local atomic order, and about phase transformations and different processes leading to the formation of quasicrystalline order.