Korean Journal of Materials Research ISSN:1225-0562(Print) 2287-7258(Online) 한국재료학회지

The high temperature deformation behavior of Ni₃Al and Ni3(Al,Mo) single crystals that were oriented near <112> was investigated at low strain rates in the temperature range above the flow stress peak temperature. Three types of behavior were found under the present experimental conditions. In the relatively high strain rate region, the strain rate dependence of the flow stress is small, and the deformation may be controlled by the dislocation glide mainly on the {001} slip plane in both crystals. At low strain rates, the octahedral glide is still active in Ni₃Al above the peak temperature, but the active slip system in Ni₃(Al,Mo) changes from octahedral glide to cube glide at the peak temperature. These results suggest that the deformation rate controlling mechanism of Ni₃Al is viscous glide of dislocations by the <110>{111} slip, whereas that of Ni₃(Al,Mo) is a recovery process of dislocation climb in the substructures formed by the <110>{001} slip. The results of TEM observation show that the characteristics of dislocation structures are uniform distribution in Ni₃Al and subboundary formation in Ni₃(Al,Mo). Activation energies for deformation in Ni₃Al and Ni₃(Al,Mo) were obtained in the low strain rate region. The values of the activation energy are 360 kJ/mol for Ni₃Al and 300 kJ/mol for Ni₃(Al,Mo).