Plastic deformation of single crystals of Ti5Si3 with the hexagonal D88 structure

The deformation behavior of Ti5Si3 single crystals with the hexagonal D88 structure has been investigated in compression as a function of crystal orientation in a temperature range from 1200 to 1500°C. Three different types of deformation modes: {1¯100}[0001] prismatic slip, {2¯1¯12}1/3<2¯1¯1¯3> pyramidal slip and {2¯1¯18}<8¯4¯4¯3> twinning were identified for the first time as being operative in Ti5Si3 at temperatures above 1300°C, depending on the loading axis orientation. The critical resolved shear stresses (CRSS) decrease steeply with increasing temperature for all deformation modes. The values of the CRSS for {1¯100}[0001] prismatic slip are considerably lower than those for {2¯1¯12}1/3<2¯1¯1¯3> pyramidal slip, but are comparable to those for {2¯1¯18}<8¯4¯4¯3> twinning. The favored deformation modes are discussed on the basis of anisotropic elasticity theory of dislocations.