LOW-TEMPERATURE DEFORMATION OF SINGLE-CRYSTALS OF A D0(19) COMPOUND WITH AN OFF-STOICHIOMETRIC COMPOSITION (TI-36.5 AT-PERCENT AL)

Deformation behaviour of a D0(19) compound with an off-stoichiometric composition of Ti-36.5 at.% Al has been studied as a function of orientation at temperatures from -196-degrees-C to room temperature in compression. The critical resolved shear stress (CRSS) for {1100BAR}[1120BAR] prism slip and (0001)[1120BAR] basal slip increases with decreasing temperature. a dislocations introduced by prism slip have a tendency to align along their screw orientation at -196-degrees-C, but the tendency becomes less marked with increasing temperature so that at room temperature these dislocations do not necessarily align along any particular crystallographic orientations. The CRSS for {1121BAR}[1126BAR] pyramidal slip shows a minimum in the CRSS-temperature curve at a temperature T(min) between -196 and -100-degrees-C. Most 2c + a dislocations are in screw orientation at temperatures below T(min) where the CRSS increases with decreasing temperature, whereas at temperatures above T(min), where the CRSS anomalously increases with increasing temperature, the relative density of 2c + a dislocations in edge orientation with respect to those in screw orientation increases with increasing temperature so that at room temperature the edges dominate the deformation structure.