TEM study of the friction stress acting on edge dislocations in Ni3Al

Highly curved edge dislocations gliding on primary (111) planes are frequently observed in addition to the dominance of screw dislocations in L12 ordered Ni3Al deformed at 400 °C, a temperature within the anomalous temperature regime. The detailed analysis of transmission electron microscopic (TEM) images using tilting experiments proves that the superlattice dislocations of near-edge character contain superjogs consisting of segments dissociated on both (111) planes and cube cross-slip planes. Based on the TEM observations and on stress calculations two processes are proposed for the formation of the superjogs: firstly, a double cross-slip process of the screws via the cube cross-slip plane and secondly, the reaction of primary dislocations gliding on (111) with primaries cross-slipped onto (010). Since these superjogs contain segments on the cube cross-slip plane their mobility is low causing a high friction stress acting on the edge dislocations gliding on (111); as a consequence work hardening will be affected.