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Appendix B. Site Reports—Europe 181
superconductor. Mechanical alloying of Ag and Cr 2 O 3 powders is followed
by cold pressing, annealing in dry hydrogen, hot pressing at 500°C, and
finally hot extrusion at 700°C. The mechanical alloying times were
apparently too short in the initial study to provide a uniform distribution of
the 40 nm Cr 2 O 3 particles. A bimodal grain structure was observed with
mean sizes of 10 µm and 0.3 µm composed of 60% pure Ag grains and 40%
Ag grains with the nc oxide dispersoids. Even so, significant Hall-Petch
hardening was observed at room temperature, along with increased creep
resistance at 500°C in the dispersion-hardened Ag. Another project focuses
on mechanical alloying of Ll 2 –(Al,Cr) 3 Ti intermetallic with Y 2 O 3 nanoscale
dispersoids of 5 nm size.
Dr. Roland Scholl
Fraunhofer Institute, Institute for Applied Materials
Research, Department for Powder Metallurgy and
Composite Materials
Dr. Scholl described an in situ data acquisition and monitoring system for
a planetary ball mill. This is important for studies of the mechanical
alloying/milling processes used for formation of nanocrystalline materials.
The device measures the temperature and pressure via a transmitter in the lid
of the milling vial. This was done for a Fritsch “pulverisette 5” planetary
mill; the work was partially supported by Fritsch. An example was given for
milling of Ti and C powders to form TiC. Good time resolution, about 10
ms, is available to monitor the reactions, which can occur during milling and
provide feedback to optimize the milling parameters.
After the formal presentations and discussions, the WTEC visitors were
given a tour of the IFW laboratories. We observed very impressive state-ofthe-art
facilities for processing, characterization, and property testing. The
dedicated EELS facility referred to in the work of Dr. Golden (above) was
particularly noteworthy.