Abstract
Dislocation movements during plastic deformation of L12-ordered Ni3(Al, Ti) single crystals at temperatures between 90 and 873 K have been investigated in-situ by high voltage electron microscopy. Either or both of the two slip systems, {111} octahedral slip and {100} cube slip, operated depending upon the testing temperature and the orientation of tensile axis of the specimen. Movements of {111} slip dislocations were quick and jerly. Once screw dislocations ceased to move, they were immobilized instantaneously. Movements of {100} slip dislocations were smooth and viscous showing high friction stress for the cube slip. The present observations have shown that the positive temperature dependence of the yield stress of γ′-Ni3(Al, Ti) can not be attributable to the intersections between {100} and {111} slip dislocations but to the increasing difficulty of the movements of individual screw dislocations in the {111} slip system with increasing temperature.
