An Overview of the Temperature Dependence of the Strength of the Ni3Al System
AbstractMany L12 ordered alloys including the Ni3Al intermetallic system are noted for their anomalous temperature dependence of strength. It is also generally accepted that this dependence is due to a thermally assisted cross-slip, work hardening based model [1,2]. An alternative antiphase boundary (APB) based model has long been dismissed by the research community because prior calculations of APB energy, and some measurements, have shown that the appropriate APB energy of Ni3Al should remain constant with temperature [3]. These aspects will be reviewed briefly and will serve as a basis for a presentation of some more recent results. These will include the strain rate insensitivity of strength versus temperature in the increasing strength temperature region, a result that is, in our view, rather contradictory to the thermally assisted cross-slip model. Some very recent calculations of equilibrium APB energies will also be reviewed in the context of the strength dependence issue. These results show that the equilibrium APB energy increases with temperature. The question of what role, if any, equilibrium APB plays in the deformation and strengthening process will be discussed.