抄録
The effect of Co addition up to 1.5 at% on the temperature dependence of yield stress in Ni3Ge with Ll2 structure has been investigated. Flow stress measurements were made on (Ni, Co)3Ge single crystals with several different orientations. Slip systems were determined by two-surface trace analysis after compression at various temperatures between −196 and 600°C. Comparing the result of (Ni, Co)3Ge with that of the binary Ni3Ge, we obtained the following conclusions: The mechanical behavior of (Ni, Co)3Ge is essentially the same as that of the binary Ni3Ge. However, the Co addition lowers the peak-strength temperature of the binary Ni3Ge at which the slip system changes from (111)[10\bar1] into (001)[1\bar10]. The drop of this temperature is orientation-dependent and governed by the relative change in critical resolved shear stress between the (111)[10\bar1] slip system and the (001)[1\bar10] slip system due to Co addition. The change in CRSS for the (111)[10\bar1] slip system due to Co is discussed in terms of a mechanism in which a part of the leading, a⁄3[2\bar11] superlattice Shockley partial cross-slips from a (111) plane onto a (010) plane.
