Abstract
	The morphology of the room-temperature tensile tested structure of the stoichiometric directionally solidified Ni3Al was investigated using the optical and SEM microscopy analysis. The brittle intergranular fracture was dominant on fracture surfaces, however the transgranular cleavage, as well as domains of localised higher ductility with ductile transgranular or mixed fracture were observed in fractographic analysis. Comparison of the width and the spacing of bands and steps on the metallographic samples and on the cleavage fracture supports the possibility of the plastic deformation mode by the mechanical twinning produced beside the motion and slip of dislocations in the intermetallic alloys Ni3Al.