Ni Al, an interrnetallic compound with the B2 ordered structure. exhibits potential as a viable high temperature structural material. However. before this material (and other interrnerallics) can be of practical use a number of technical problems must be overcome. including lack of ductility al the room temperature. In an attempt lO address the brittleness of NiAI. and based on a premise that grain refinement may lead lo significant ductility improvements mechanical alloying and nanocrysialline synthesis were used to produce fine-grained NiAI. The mechanically alloyed NiAI with an average grain size of about 0.5 μm, unlike its coarse grained. cast counterpart, exhibits a notable room temperature compressive ductility due to two contributing microstructural factors: i) the development of the< 110> texture during hol extrusion leading to the activation of additional slip systems. and ii) the predominance of low angle grain boundaries. In the nanocrystalline form, NiAI with an average grain size in the range from 2 lo I O nm, exhibits measurable room temperature ductility in biaxial disc bend tests. unlike its coarse-grained counterpart. This observation can be explained assuming that diffusional, rather than dislocation, mechanisms control plastic deformation of the nanocrysralline NiAI. The emphasis of the present paper is on rationalizing the improved room temperature ductility in mechanically alloyed and nanocrystalline NiAI. The most significant conclusion of the present discussion - contrary lo widespread beliefs - is that the grain size plays only an indirect role in controlling ductility.

The CuAl5 single crystal with the initial orientation (I 10)[00I] was cold rolled and subsequently compressed in a channel die in such a way that the new direction of plastic flow was parallel to the transverse direction of initial rolling and the compressed plane was parallel to the former rolling plane. The dislocation slip was the only deformation mechanism during rolling. The dislocation substructure after rolling was uniform. During the compression in a channel die, additionally, the deformation twinning as well as the shear band formation took place. The recrystallization commenced and proceded within the shear bands. After that. the recrystallization proceeded by the nucleation and growth of new grains within the areas with high density of deformation twins. The recrystallized regions of the former shear bands were filled by fine grains while the regions amongst them exhibited much bigger grains. The recrystallization texture was formed according to the theory of the oriented growth.

The formation of texture and microstructure in polycrystalline Cu and Cu-5 wt. % Al alloy during two modes of homogenous rolling have been compared. Two samples of each metal were rolled. One sample was rolled unidirectionally, while the other by reverse rolling. Some differences in the textures depending on the rolling mode have been observed in the range of deformation of the Cu-5 wt. % Al alloy where intensive twinning took place. It was also found that the texture of reverse rolling was more homogeneous across the thickness of the rolled alloy sheet than the texture of unidirectionally rolled material. No clear effect of the rolling mode on microstructure has been observed.