Dresden 2003 – scientific programme

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M: Metallphysik

M 41: Postersitzung

M 41.25: Poster

Thursday, March 27, 2003, 14:30–16:30, HSZ

Plastic deformation of MoSi₂ single crystals along ⟨ 110 ⟩ — •Christian Dietzsch, Martin Bartsch, and Ulrich Messerschmidt — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle/Saale, Germany

MoSi₂ single crystals have been deformed along a soft ⟨ 110 ⟩ compression axis to activate dislocations with ⟨ 100 ⟩ Burgers vectors. The flow stress shows a strong anomalous increase between 500 and 740 ^oC. The strain rate sensitivity is relatively high at low temperatures and above the anomaly range but very low within it. There, it depends inversely on the strain rate. The dislocation structures were studied by high-voltage transmission electron microscopy. While at lower temperatures the dislocations are curved, they become straight and crystallographically oriented in the anomaly range. The results are compared with those of deformation along a soft ⟨ 201 ⟩ direction, which activates dislocations with 1/2⟨ 111⟩ Burgers vectors. Based on the characteristics of the strain rate sensitivity and the dislocation shape, the flow stress anomaly is interpreted by a dissociation of the dislocations, which requires so-called conservative climb during the motion and leads to strain ageing effects.