A weak-beam analysis of dissociation modes of superlattice dislocations in Ni3(Al, Ti)

Dislocation mechanisms and their influence on mechanical properties (e.g. flow stress and work-hardening) can be studied in detail by critical prestraining experiments. In this study, the influence of prestrain on the flow stress of an Ni3(Al, Ti) alloy with L12 long-range order structure was investigated. The yield strength has a positive temperature dependence (it increases with increasing temperature) from room temperature (RT) up to 450 °C. Prestraining of Ni3(Al, Ti) single crystals at 800 °C activated the primary ± a[110](001) cube slip system. Climb dissociated segments interconnect superlattice dislocations of Lomer-Cottrell (LC) type. A subsequent additional deformation at RT introduced superlattice dislocations of the primary ± a[101](111) glide system. This subsequent deformation results in almost the same flow stress as the flow stress found in single crystals subjected to RT deformation only. Prestraining was found to have a huge influence on work-hardening. This is consistent with dislocation interactions of cube and octahedral glide systems. It is concluded that yielding is an intrinsic property of dislocation motion due to extended core configurations.