The low-temperature plastic deformation of α-titanium and the core structure of a-type screw dislocations

Abstract

Abstract α-titanium single crystals, containing three different amounts of interstitial impurities, have been tested in compression at temperatures between 77 and 700 K. The mechanical behaviour is characterized by a strong temperature dependence of the yield stress for slip on the primary prismatic slip plane (1010)[1210], a strong dependence of the critical resolved shear stress on the orientation of crystal axis and the failure of the Schmid law, an anomaly at temperatures between 300 and 500 K which is associated with cross-slip into a first-order pyramidal plane, and the occurrence of two hardening stages on the deformation curves at low temperatures. Both conventional and in situ transmission electron microscopy examinations revealed that a large lattice friction opposes the motion of a-type screw dislocations at temperatures below 550 K. Since edge dislocations are found to be highly mobile, it appears that, at low temperatures, the yield stress of pure α-titanium is governed by a Peierls force act...