The Effect of Co on the Temperature Dependence of Yield Stress in Ni₃Ge Single Crystals

Abstract

The effect of Co addition up to 1.5 at% on the temperature dependence of yield stress in Ni₃Ge with L1₂ 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 maximum-yield stress temperature of the binary Ni₃Ge at which the slip system changes from (111)[\bar101] into (001)[\bar110]. The drop of this temperature is orientation-dependent and governed by the relative change in critical resolved shear stress between the (111)[\bar101] slip system and the (001)[\bar110] slip system due to Co addition.