Plenarvorträge - DPG-Tagungen

Metallphysik Donnerstag
M 25 Mechanische Eigenschaften III
Zeit: Donnerstag 10:15–11:15 Raum: H4
M 25.1 Do 10:15 H4
Modelling modulus mismatch strengthening for dislocation dynamics
simulations — •Volker Mohles — Institut für Materialphysik,
Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster
Modulus mismatch strengthening is investigated by simulating the
glide of dislocations through obstacle fields and determining the critical
resolved shear stress. For the interaction between dislocations and
the modulus mismatched particles a heuristic stress function is assumed.
This is necessary because a an accurate treatment is not known; moreover
the computational effort for such a treatment would be too high at
present. The heuristic stress function accounts for the interaction’s essential
properties, like symmetry operations and the dependence on the
magnitude of the Burgers vector. The coefficients of this function are
to be adjusted to atomistic simulations (Embedded Atom Method, e.g.
Nedelcu et al., Osetsky et al.).
M 25.2 Do 10:30 H4
Computer Simulations of carbon and vacancy related anelasticity
in Fe-Al. — Mikhail S. Blanter 1 , •Igor S. Golovin 2 , and
Hans-Rainer Sinning 2 — 1 Moscow State Academy of Instrumental
Engineering and Information Science, Moscow, Russia — 2 TU Braunschweig,
Institut fuer Werkstoffe, Langer Kamp 8, D-38106 Braunschweig
Special attention is paid in this research to the interpretation of the
S and X peaks (see previous abstracts) in Fe-Al alloys. Peculiarities of
carbon diffusion in Fe-Al alloys were studied as a function of interatomic
C-Fe, C-Al, C-C, and C-vacancy interactions. Parameters of carbon mobility
in solid solution were evaluated using temperature-dependent internal
friction measurements (the S and the X relaxation). The ordering of
Al atoms enhances C diffusion in the Fe-Al solid solution, while a high vacancy
concentration and carbon-vacancy interaction lead to a new relaxation
effect with higher activation energy (so-called the X peak). Parameters
of the carbon-vacancy interatomic interaction in D03 ordered Fe-Al
alloys and correspondingly parameters of the X peak depend on positions
which are occupied by vacancies. The employed atom-interaction model
is based on the long-range strain-induced (’elastic’) interaction supplemented
by a short-range ’chemical’ interaction. The model assumes that
the interactions of dissolved atoms affect both the distribution (shortrange
order) and energies of carbon atoms and consequently the activation
energy of their diffusion.
M 25.3 Do 10:45 H4
Mechanical Spectroscopy of Fe-(0-40at.%)Al alloys. — •Igor S.
Golovin 1 , Alexander Strahl 2 , Svetlana B. Golovina 2 , Tatjana
Pavlova 3 , and Hartmut Neuhäuser 2 — 1 TU Braunschweig,
Institut fuer Werkstoffe, Langer Kamp 8, D-38106 Braunschweig — 2 TU
Braunschweig, Institut für Metallphysik u. Nukleare Festkörperphysik,
Mendelssohnstr. 3, D-38106 Braunschweig — 3 Physics of Metals Department
of Tula State University, Tula, Russia
M 26 Nanoskalige Materialien IV
Iron-Aluminium alloys in ordered and quasi disordered states have
been investigated after various thermal (quenching, annealing) and mechanical
(cold work) treatments to find out the origin of a few internal
friction peaks observed. As main instrumentation the vibrating-reed
technique with simple beam and an tuning-fork shaped specimen and
inverted torsion pendulum were used. The aluminium concentration was
varied from 6 up to 40 at.%. The temperature and amplitude dependence
of damping and of Young’s modulus has been measured, during
heating / cooling cycles between 80 and 920K. Various damping peaks
including the Snoek-type peak (S peak), X peak, Zener (Z) peak and a
low temperature dislocation-related (D) peak have been systematically
studied with respect to alloy composition and ordering. The mechanisms
of these peaks are discussed. Additional alloying by Cr, Ti, Nb (less than
2%) was used to distinguish between carbon and vacancy contribution
to internal friction.
M 25.4 Do 11:00 H4
Mechanical Spectroscopy of Fe-Al-Cr, Fe-Al-Si, Fe-Al-Co
alloys. — •Alexander Strahl 1 , Igor S. Golovin 2 , Tatjana
Pavlova 3 , Heiko Bremers 1 , Christa Grusewski 2 , and Hartmut
Neuhäuser 1 — 1 TU Braunschweig, Institut für Metallphysik u.
Nukleare Festkörperphysik, Mendelssohnstr. 3, D-38106 Braunschweig
— 2 TU Braunschweig, Institut fuer Werkstoffe, Langer Kamp 8,
D-38106 Braunschweig — 3 Physics of Metals Department of Tula State
University, Tula, Russia
Our investigation of internal friction in binary Fe-Al alloys (see previous
abstracts) has been extended to ternary Fe-Al-Cr, Fe-Al-Si, and
Fe-Al-Co alloys with a fixed content of substitute atoms in iron: [Fe-
(Al,Cr)30, Fe-(Al,Si)25, Fe-(Al,Co)25 at.%]. The idea of studying internal
friction in these compositions is based on the opportunity to vary the
degree of order in the alloys and the formation of carbides: Si improves
D03 order in Fe-Al, Co increases the tendency to the B2 order into Fe-
Al, and substitution of Al by Cr decreases the order in Fe-Al and also
forms the chromium carbides. The structure of the alloys was carefully
examined using X-ray and TEM, the order-disorder transition intervals
by DSC measurements. Temperature and amplitude dependent internal
friction effects were studied in Hz and kHz ranges of resonance frequency
with a heating rate of 1K/min (the same heating rate was used in DSC
measurements).
Zeit: Donnerstag 11:45–12:45 Raum: H16
M 26.1 Do 11:45 H16
Synthesis and Copper Intercalation Studies of Nanostructured
Transition Metal Sulphides — •H. A. Therese, F. Rocker, E. W.
Finckh, J. Li, A. Gloskovskij, G. H. Fecher, G. Schönhense,
U. Kolb, and W. Tremel — Johannes Gutenberg - Universität, 55099
Mainz
Research on nanostructure materials has grown exponentially during
the last decade due to their interesting properties exhibited by quantum
confinement of electrons. In particular, the ability of layered materials to
curl up into nanotubes has drawn the attention of many scientists which
in turn opened up a new era in nanotechnology. Further, layered transition
metal chalcogenides have potential applications as cathode materials
for rechargeable high-energy density lithium batteries, as catalysts for hydrosulfurisation
or as lubricants. The main goal of our research is to synthesise
nanostructured transition metal sulphides and studying their behaviour
if intercalated by copper. Nanostructured MoS2 (amorphous) was
prepared by thermal decomposition of (NH4)2Mo3S13 x H2O at 720K in
sealed tubes and nanotubes of MoS2 were prepared by coating technique
using SiO2 tubes as template. Intercalation of Cu into MoS2 was carried
out by computer-controlled galvanostatic cathodic reduction of MoS2
with a three electrode arrangement. The samples were characterised by Xray
diffraction (XRD), High resolution transmission electron microscopic
(HRTEM) and X-ray absorption spectroscopic (XANES) techniques.
M 26.2 Do 12:00 H16
Agglomerationsverhalten von SiO2- und Al2O3-Nanopulvern in
wässrigen Lösungen verschiedener Ionenkonzentration zur Herstellung
von Nickeldispersionswerkstoffen — •Gabriele Vidrich,
Jean-Frederic Castagnet und Hans Ferkel — Institut für
Werkstoffkunde und Werkstofftechnik, TU Clausthal, Agricolastraße 6,
38678 Clausthal-Zellerfeld
Im Rahmen der Koabscheidung von keramischen Nanopulvern und Metallen
aus galvanischen Bädern ist das Dispersions- und Agglomerationsverhalten
der Partikel im Elektrolyten von wesentlicher Bedeutung, da