Effect of substitutational elements on plastic deformation behaviour of NbSi 2-based silicide single crystals with C40 structure

Abstract

Plastic deformation behaviour of binary NbSi 2 and ternary NbSi 2-based silicide single crystals with the C40 structure was examined at high temperatures and compared with the results in MoSi 2 with the C11 b and TiSi 2 with the C54 structure, focusing on anomalous strengthening. Addition of substitutional alloying elements affected the anomalous strengthening in NbSi 2-based silicides; addition of Mo and W strongly affected the anomalous strengthening, while Ti and Al additions showed little effect. The substitutional impurity atoms may gather and form a dragging atmosphere around 1/3〈21̄1̄0] moving dislocations containing a superlattice intrinsic stacking fault in NbSi 2-based silicides, resulting in anomalous stress increase. The effect of the dragging atmosphere and diffusion path of additional elements on an anomalous strengthening is discussed, focusing on the atomic arrangement on slip planes and the phase stability of the C40 structure with respect to the C11 b and C54 structures.