Tensile deformation and fracture behaviour in NbSi2 and MoSi2 single crystals Original Research Article

Tensile deformation behaviour in NbSi2 and MoSi2 single crystals with the C40 and C11b structure, respectively, was examined in a temperature range up to 1500 °C and compared with that under compression, focusing on the temperature dependence of the critical resolved shear stress (CRSS), elongation/fracture strain and crack initiation process. Two different types (Type A and Type B) of geometry of NbSi2 tensile specimens were used to evaluate elongation and fracture behaviour. No difference in the CRSS for the 000121̄1̄0 slip of NbSi2 and that for the {011)<100] slip in MoSi2 was found in both modes of tension and compression. In contrast, the ductile-brittle transition temperature (DBTT) depended strongly on the loading mode and the type of geometry. Elongation and process for crack initiation in NbSi2 changed remarkably depending on the deformation temperature. Four new slip systems of 101̄01312̄10, 101̄11312̄10, 101̄00001 and 112̄Y112X (X×Y=−6) were found near the crack path in NbSi2 deformed at 1000 °C.