High-temperature creep behavior in Ni3(Al, Ta) single crystals with different orientations

Abstract

High temperature creep behavior of a nickel-rich Ni3(Al, Ta) with the Ll2 structure is investigated in order to clarify the influence of crystallographic orientation. The single crystals with four different orientations are deformed in compressive creep at the temperatures ranging from 1123 to 1273 K under a constant load with initial shear stresses being from 35 to 120 MPa for the (111)[101] slip system. The results show a distinct orientation dependence of creep strength, although shape of creep curves, stress exponent and the activation energy seem to be independent on orientation. It is shown, however, that the internal stress measured by strain transient dip tests is found to be orientation-dependent and that the creep behavior is independent on orientation if these are analyzed with the effective stress instead of the applied shear stress.