Q. Feng et Sh. Whang, Deformation of Ti-56At.%Al single crystals oriented for single slip by 1/2< 110] ordinary dislocations, ACT MATER, 48(17), 2000, pp. 4307-4321
Anomalous hardening by single (111) slip of ordinary dislocations (1/2[110]
) has been investigated using gamma -Ti-56Al single crystals. The uniaxial
compressive deformation was conducted in four different orientations, [(3)
over bar 12 7], [(1) over bar 6 3], [(1) over bar 12 5] and [(1) over bar 7
2] between 196 K and 1173 K. It was found that the single slip of ordinary
dislocations in this alloy occurred in three different orientations, [(3)
over bar 12 7], [(1) over bar 6 3] and [(1) over bar 12 5] between 673 K an
d 1073 K. Strong orientation dependence in CRSS for the three deformation o
rientations is associated with the magnitude of the Schmid factor for cross
-slip in the (110) plane. The dislocation structure of the deformed specime
ns showed that the cross-slip in the (110) plane increased with temperature
in all three orientations. The main dislocation structures from (110) cros
s-slip at these temperatures were double cross-slip configurations, dipoles
and dislocation loops. The anomalous hardening by ordinary dislocations at
high temperatures can be explained well by the (110) cross-slip model. Bas
ed on the model, the activation energy for the (110) cross-slip was found t
o be 0.45 eV. In addition, the Cottrell-Stokes type temperature-change expe
riments were conducted under the single slip of ordinary dislocations at 67
3 K and 873 K. The results show that the yielding behavior isn't thermally
reversible probably due to (110) cross-slip in this alloy. (C) 2000 Publish
ed by Elsevier Science Ltd on behalf of Acta Metallurgica Inc.