Low-temperature deformation of single crystals of a DO19compound with an off-stoichiometric composition (Ti-36·5 at.% Al)

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Abstract
Deformation behaviour of a DO19, compound with an off-stoichiometric composition of Ti-36·5 at.% Al has been studied as a function of orientation at temperatures from −196°C to room temperature in compression. The critical resolved shear stress (CRSS) for {1100} 〈11 20〉 prism slip and (0001)〈1120〉 basal slip increases with decreasing temperature. a dislocations introduced by prism slip have a tendency to align along their screw orientation at −196°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 {1121} 〈1126〉 pyramidal slip shows a minimum in the CRSS-temperature curve at a temperature T min between −196 and −100°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.