Mechanical properties of the ordering alloy Cu 2NiZn

Abstract

The mechanical properties characterizing the true stress-true strain curve of Cu 2NiZn are investigated as a function of the deformation temperature between 77 and 343 K and as a function of the quench temperature in compression as well as in tension. The behaviour of the yield stress could be explained in terms of the stress necessary to operate an initially edge-oriented Frank-Read source, consisting of a superlattice dislocation with a length of 1.45 μm and to destroy the short-range order across the slip plane. The behaviour of the strain hardening coefficient could be accounted for by the superposition of the strengthening due to interacting and non-interacting forest dislocations, formation of jogs and APB-tubes and long-range stresses. The stress σ III at the onset of stage III behaves according to the {111} cross-slip model for the disordered alloy. Its behaviour for the ordered alloy can be explained by movement of single dislocations, leaving sheets of APB in its wake. The mechanical properties of the ordered L1 0 and L1 2 structures behave about the same, whereas the behaviour of the disordered alloy is quite different. The same behaviour holds for the dislocation microstructure as observed by transmission electron microscopy.