Plastic Behaviour in Ni3(Al, X) Single Crystal–Temperature, Strain-rate, Orientation and Composition–

The shear stress data for L12 single crystals for more than 50 kinds have been already complied. The fact that the ternary additive is inevitable to facilitate the single crystal growth of Ni3Al is rather fortunate for us, because its selection is widely different by individual workers, and this situation enables us to evaluate the effect of ternary elements on the plastic behaviour in Ni3(Al, X) single crystals. Referring to the comprehensive data for polycrystalline Ni2(Al, X), the solid solution hardening of the CRSS for octahedral slip at low temperatures and the positive temperature dependence of the CRSS for octahedral slip are evaluated mostly on Ni3(Al, X) single crystals in terms of the effects of compositions including both the deviation from stoichiometry and the ternary additions, and the effect of orientations of the stress axis. Above the temperature showing the maximum strength, the behaviour of the CRSS for cube slip controlled by Peierls mechanism and the CRSS for octahedral slip controlled by viscous motion of dislocations are analysed in terms of the dependent variables of temperature, strain-rate, orientation and compositions. Comparison of the plastic deformation is also extended to other L12 compounds such as Ni3Ga, Ni3Ge, Co3Ti and Pt3Al, which exhibit a big contrast each other. Also pointed out is the areas where the future research and development will be needed.