Investigation of slip transmission behavior across grain boundaries in polycrystalline Ni₃Al using nanoindentation

The influence of grain boundaries on material deformation in Ni₃Al was investigated by relating the material pile-up at grain boundaries and the propagation of slip across grain boundaries to the misorientation between the corresponding grains. Indentation tests were carried out using micro- and nanoindentation at distances shorter than the radius of indent size from a grain boundary on Ni₃Al. The indents were observed using scanning electron microscopy and non-contact-mode atomic force microscopy. Repeated experimentation did not reveal a rising trend of hardness near grain boundaries, indicating that hardness is not a sensitive parameter to measure grain boundary strengthening effects. However, it was observed that the slip transfer behavior across a grain boundary has a strong dependence on a local misorientation factor m′ relating the misorientation of slip planes and slip directions on either side of the grain boundary. This result agrees with the fundamental assumption in the physical explanation of the Hall–Petch effect.