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M: Metallphysik

M 49: Grenzfl
ächen I

M 49.3: Vortrag

Dienstag, 8. März 2005, 15:15–15:30, TU H2038

In situ measurements of grain boundary migration with a high magnetic field polarization microscopy probe — •Peter Konijnenberg, Dmitri A. Molodov, and Günter Gottstein — Institut für Metallkunde und Metallphysik, RWTH-Aachen, 52074 Aachen

A space resolving high magnetic field polarization microscopy probe has been developed to track grain boundaries at the surface of magnetically anisotropic metals during magnetic annealing at high field strengths. It is known from experiments that also in non-ferromagnetic anisotropic materials a sufficient driving force for grain boundary migration can be provided by external high magnetic fields.Two major advantages in this approach are a constant, adjustable and accurately known driving force and the possibility to drive plane grain boundaries with a uniform and well defined boundary structure.

In essence this probe comprises a conventional polar magneto-optic Kerr setup; a remote controlled monochromatic polarizing microscope with CCD camera in field direction and a sample chamber equipped with a resistance heated sample stage perpendicular to the field direction. With a diameter of 50mm this device fits inside bore holes of commonly accessible resistive high field magnets. The current configuration was tested for sample temperatures up to 673K and fields of 25T.

The first ever in-situ boundary migration observation during magnetic annealing is presented. Absolute boundary mobilities and energies of various asymmetric tilt and twist boundaries in high purity Zn (99.99+%) bicrystals as well as grain growth kinetics data from polycrystalline samples are discussed as a function of temperature and driving force.