Fe-6at%Si bicrystals were observed by in situ X-ray topography with a monochromatic beam during a compression test by surface reflection. The primary slip system was the same in both grains. As the specimen contained sub-grain boundaries, it had to be rocked during exposure in order to ensure imaging of the entire gauge length. Images were recorded both on X-ray films (rocking with the specimen) and using a fixed X-ray camera. The distortions of the images were used to investigate stress repartition in the whole specimen and local stress concentrations at points where slip bands met the grain boundary. In the present case, slip transfer through the grain boundary was apparently easy. However, a careful analysis of stresses within the specimen showed it was not the case. In Fe 6% Si, the creation and motion of slip bands was very sensitive to local stress. Transmission occurred on the most stressed surface, at the tip of slip bands containing a few hundred dislocations. The transmitted slip bands then propagate through the bulk of the specimen to less stressed areas. A careful analysis using all available experimental data is, thus, necessary in order to avoid misinterpretation.

Dislocation Transmission through a Σ = 3 Grain Boundary in Fe-6at%Si - in situ Experiments in Compression Specimen. A.Jacques, A.George, M.Polcarova, J.Bradler: Nuclear Instruments and Methods in Physics Research B, 2003, 200, 261-6

 Table 4

 Chemical Diffusivity in Ordered (L10) FePt

 a:     D (m2/s) = 6.76 x 10-4 exp[-3.17(eV)/kT]

 c:     D (m2/s) = 7.59 x 10-2 exp[-3.80(eV)/kT]