Effect of substitutational elements on plastic deformation behaviour of NbSi2-based silicide single crystals with C40 structure

Plastic deformation behaviour of binary NbSi2 and ternary NbSi2-based silic ide single crystals with the C40 structure was examined at high temperature s and compared with the results in MoSi2 with the Cl1(b) and TiSi2 with the C54 structure, focusing on anomalous strengthening. Addition of substituti onal alloying elements affected the anomalous strengthening in NbSi2-based silicides: addition of Mo and W strongly affected the anomalous strengtheni ng, while Ti and Al additions showed little effect. The substitutional impu rity atoms may gather and form a dragging atmosphere around 1/3[2<(11)over bar>0] moving dislocations containing a superlattice intrinsic stacking fau lt in NbSi2-based silicides, resulting in anomalous stress increase. The ef fect of the dragging atmosphere and diffusion path of additional elements o n an anomalous strengthening is discussed, focusing on the atomic arrangeme nt on slip planes and the phase stability of the C40 structure with respect to the Cl1(b) and C54 structures. (C) 2000 Acta Metallurgica Inc. Publishe d by Elsevier Science Ltd All rights, reserved.