Münster 1997 – scientific programme

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M: Metallphysik

M 10: Kristallplastizit
ät I

M 10.6: Talk

Tuesday, March 18, 1997, 17:10–17:30, S 8

Deformation Instabilities in Oriented Lamellar Two-Phase Titanium Aluminides — •P. Szászvári, H. Heinrich, and G. Kostorz — Institut für Angewandte Physik, ETH Zürich, CH-8093 Zürich

The mechanical properties of uniaxially aligned polysynthetically twinned two-phase γ −α₂ titanium aluminides are characterised by a strong orientation dependence. If the lamellae are oriented parallel or perpendicular to the deformation axis, the yield stress is particularly high. For these orientations serrations in the stress-strain curves occur, whereas they are absent for other orientations of the lamellae to the compression axis. Compared with Ti-48 at.% Al the deformation instabilities are reduced by alloying with 1 at.% Cr. The propagation of deformation by twinning across lamellar interfaces is proposed to be responsible for serrated flow in these materials. The transfer of deformation across the boundaries of the lamellae is strongly influenced by the tetragonality of the γ phase and the Schmid factors of the slip systems and twinning systems.