The unstable behaviour of the nominally stable single crystal samples of f.c.c. metals and alloys subdued to uniaxial straining is due, first of all. to two factors: the deviation of the crystallographic orientation from the nominal [uvw] direction, and imperfection of the inner structure, being the source of 'texture in a single crystal'. It is evident that in deformed single crystals the only parameter, which has an essential effect on plastic anisotropy, is crystallographic orientation. Thus. it is possible to evaluate the variation of crystallographic orientation at the tensile test indirectly, basing on the change of the strain ratio. This statement explains the significance of the strain ratio r vs. strain c function in the analysis of instability of crystallographic orientation in single crystals subdued to the tensile test. In the previous papers the authors have revealed the change of the strain ratio with the strain in several low stacking fault energy copper alloys and silver, and in medium s.f.e. copper. The present paper constitutes. in a way, a supplement to these results. describing the instability of the strain ratio and crystallographic orientation in the high stacking fault energy nickel single crystals. The present paper should be considered as an attempt to explain the different characteristics of instability in nominally stable [ 100], [111] and [110] f.c.c. single crystals.

Using SHSB technique, composites "in situ" based on intermetallic phase Ni3Al reinforced with particles of titanium carbides or borides were fabricated. The reinforcing phase was generated by spontaneous exothermic reaction proceeding in metal bath in a metaVnon-metal powdered briquette. Thus fabricated composites were free from porosity, possessed high thermodynamic stability and were characterised by absence of chemical reactions at the matrix-reinforcing particle phase boundary, which effectively prevented structure degradation under high-temperature service conditions. The nucleation of the reinforcing phase in molten metal matrix produced clean interfacial surface, free from the presence of oxides and adsorbed gas, and better wettability and coherence between the matrix and reinforcing particles. Owing to the possibility of controlling the parameters of the reaction kinetics during composite synthesis it was possible to generate particles of a required diameter, volume content and distribution and to obtain, consequently, the required level of the mechanical and tribological properties. An important advantage of this method is the possibility of finally shaping by means of casting process the elements and parts of machines. In accordance with ANSI H35. I we use such nomenclature of composite for example Ni3AVfi05p - matrix Ni3AI, type of reinforcement TiC, vol fraction 5%, p - particles.