DEFORMATION UNDER SINGLE SLIP OF ORDINARY DISLOCATIONS IN SINGLE-CRYSTAL TI-56AL

Single crystals of gamma-Ti-56Al were deformed in three different comp ression orientations: [(3) over bar 12 7], [<(1)over bar 63>], [(1) ov er bar 12 5]. The yield stress and the critical resolve shear stress ( CRSS) under single slip of ordinary dislocations between 673 and 1073 K not only exhibit anomalous hardening, but also depend on deformation orientations in single crystal gamma-Ti-56Al. Each yield stress curve exhibits positive temperature dependence with a maximum value near 10 73 K. The CRSS value of each curve for a given temperature was correla ted with the Schmid factor ratio between the octahedral cross slip pla ne and the primary slip plane. The deformed specimens from various ori entations and temperatures have been investigated by TEM using two bea m and weak beam techniques. The morphology of ordinary dislocations do es not change significantly from room temperature to 1073 K. The disso ciation of ordinary dislocations was observed under weak beam in the s pecimen deformed at 873 K. (C) 1997 Elsevier Science S.A.