Deformation mechanisms in ordered Cu₂NiZn: The role of elastic and antiphase boundary energy anisotropies

Abstract

The ordered Cu₂NiZn alloy shows a change in antiphase domain structure according to the ordering temperature. At low annealing temperatures there are isotropic domains and at high temperatures there are cube-oriented domains characteristic of highly anisotropic boundary energies. The material is always elastically anisotropic and hence it is possible, within the same alloy, to compare the influences of the two types of anisotropy on dislocation microstructures and deformation behaviour.

At low temperatures, and for disordered materials, strengthening is dominated by dipole and multipole formation and tangled dislocation arrays. At elevated temperatures the ordered alloys show extensive glide on planes near {110} as well as some on {001}. For the material with cube-oriented domain boundaries there is some evidence to support point blocking of dislocations by cross-slip onto cube planes, leading to a higher work hardening at intermediate temperatures. Glide on {110} planes is favoured by the elastic anisotropy which allows easier bowing out of an initially screw-oriented dislocation segment. The multiplicity of slip systems available at elevated temperature is determined more by the elastic anisotropy than by the antiphase boundary energy anisotropy.