The defect structure in polycrystalline polytwinned FePd intermetallics with the L10 ordered structure, after room-temperature tensile testing to failure, was studied by transmission electron microscopy. The active deformation modes which were responsible for the accommodation of plastic strain included the octahedral glide of ordinary dislocations with the Burgers vector, b = ½<110>, and mechanical twinning on octahedral planes: the ordered twinning systems 1/6<112>{111}. Super-dislocations, with b = <011>, were infrequently observed and were identified as being by-products of the transfer of mechanical twins across the polytwinned interfaces; which produced glissile ordinary dislocations. The ordinary dislocation glide and the mechanical twinning were complementary deformation modes, which had to operate in a synergistic manner in alternating twin-related lamellae of the polytwinned grains in order to achieve general plasticity in the polycrystalline FePd.

Transmission Electron Microscopy of Room Temperature Deformed Polytwinned L10-Ordered FePd. H.Xu, J.M.K.Wiezorek: Acta Materialia, 2004, 52[2], 395-403