In-situ straining experiments in NiAl along soft orientations, and comparison with atomistic simulations

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 calculation s of the dislocation core structure along the screw orientation. Cross-slip also leads to the nucleation of high densities of prismatic loops. Disloca tions exhibit kinked shapes with almost no screw portion, in agreement with results of atomistic and anisotropic elastic calculations. The local stres s deduced from dislocation curvature is close to that measured in macroscop ic experiments. Peierls frictional forces are low at 300 K, but higher at 1 44 K on edge segments in planes close to {100}. The dislocations emitted at a crack tip are analysed and compared with those formed in atomistic simul ations under similar conditions.