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Plastic Deformation of Cr Single Crystals in Triple-Q State Compressed at 77 K

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Document pages: 23 pages

Abstract: A series of compression tests on chromium single crystals at 77 K was carried out in order to investigate the slip activity in the first 2-4 of plastic strain. Macroscopic samples of about 3×3×10 mm were polished mechanically and electrolytically and their orientations prior to and after deformation were determined by electron backscatter diffraction to assess the magnitudes and directions of crystal rotations. The crystals compressed in the direction close to [001] deformed primarily by slip on the most highly stressed (-101)[111] and (101)[-111] systems. Loading the crystals in the directions close to the [011]-[-111] edge of the stereographic triangle resulted in preferential twinning on {112}〈111〉 systems. For loading in the center-triangle direction, the slip morphology was dominated by anomalous slip on the low-stressed (0-11) plane in contrast to the prediction of the Schmid law. Diffraction contrast imaging in TEM reveals the presence of [100] screw junctions between intersecting 1 2[111] and 1 2[-111] screw dislocations. Using molecular statics simulations, we show that this junction is not removed under the applied stress. Instead, the three dislocations move on the (0-11) plane, which results in the anomalous slip.

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