The locking of 〈110〉 edge dislocations on {001} in L1₂ordered compounds: High-resolution electron-microscopy observations

Abstract

Abstract In the 〈110〉{001} slip system in L12 ordered alloys, both screw and edge dislocations may become locked by dissociating into nonplanar structures. In this paper the structure of edge dislocations in the [110](001) primary cube system in Ni3Ga and Ni3(Al, Ti) single crystals has been observed with weak-beam and lattice-imaging microscopy. Near 600°C the edge superdislocations are locked in the double Lomer—Cottrell lock; near 700°C the edge dislocations are locked in nonplanar structures formed by climb dissociations. Both structures have been observed directly by high-resolution electron microscopy. The implications of the locking of the edge dislocations on the operation of 〈110〉{001} and 〈110〉{111} slip systems are discussed.