Abstract
In-situ straining experiments have been carried out on NiAl single crystals, along soft orientations, at 143 and 300 K, in order to analyse the glide properties of (001) dislocations and the fracture process. The results show that dislocations slip either in {110} planes or in wavy slip surfaces as the result of intensive cross-slip, in agreement with atomistic calculations of the dislocation core structure along the screw orientation. Cross-slip also leads to the nucleation of high densities of prismatic loops. Dislocations exhibit kinked shapes with almost no screw portion, in agreement with results of atomistic and anisotropic elastic calculations. The local stress deduced from dislocation curvature is close to that measured in macroscopic experiments. Peierls frictional forces are low at 300 K, but higher at 144K on edge segments in planes close to {100}. The dislocations emitted at a crack tip are analysed and compared with those formed in atomistic simulations under similar conditions.
