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College Park, Maryland      June 6 - 10 , 2004

WP57: In-situ deformation studies using HIPPO/CRATES

S.C. Vogel, T. Medina, E. Meyer, D.J. Williams (Los Alamos National Laboratory), T. Brissier (Los Alamos National Laboratory; HTW Saarbruecken, 66117 Saarbruecken, Germany), C. Hartig, J. Laakmann, O. Meyer, H. Mecking (TU Hamburg-Harburg, 21071 Hamburg, Germany)

In-situ neutron diffraction deformation studies of metals, alloys and composites using strain derived from peak-shifts are well established for more than two decades. However, the peak-shift measures by definition only the elastic strain. To obtain further insight into the deformation mechanisms which are active to achieve a given amount of plastic deformation, the texture is also an important quantity. The texture, or orientation distribution function (ODF), is accessible via peak intensity changes in a diffraction experiment. The texture changes are differently for instance for slip, twinning or grain boundary sliding, allowing differentiation between these mechanisms by a neutron diffraction experiment. Understanding of the deformation mechanisms is of fundamental interest for modeling of materials behavior. We describe the system HIPPO/CRATES which allows to study in-situ both the anisotropic elastic strain evolution via the change in peak shift as well as the change in texture via the changes in peak intensity. CRATES, a load-frame for the High Pressure Preferred Orientation diffractometer HIPPO at LANSCE, allows to apply uni-axial stresses up to 100 kN in tension or compression to a specimen. It is equipped with rotation and translation stages for increase of pole figure coverage and alignment, respectively. HIPPO's large detector area allows to measure the full ODF with few sample rotations and provides anisotropic elastic strain information for 20 to 100 different diffraction vectors. First results from an investigation of metals with a hexagonal close packed crystal structure (Mg and Zr alloys) are presented.

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