Ordering process in Cu-18Ni-26Zn alloy

An investigation was made of the effect of low-temperature annealing on the structure and properties of strips from a Cu-18Ni-26 Zn alloy. Specimens taken from strips cold rolled at reductions from 20 to 90% and specimens from recrystallized strips were annealed within the temperature range from 473 to 773 K for 10 h. Changes in the apparent elastic limit, yield strength, tensile strength, elongation, and hardness were determined. Electron-microscope observations of changes in the alloy structure during annealing were also made. It was found that annealing of the alloy at temperatures up to 673 K improved its mechanical properties, depending on the annealing temperature and time as well as on the degree of reduction. Maximum elastic limit, yield strength, tensile strength, elongation, and hardness values were obtained in specimens subjected to the highest reductions, which were annealed at a temperature of 573 K for up to 2h. It was proved that hardening of the alloy was responsible for the ordering process taking place during the annealing treatment. The structure of an ordered alloy is characterized by the dispersional distribution of super lattice domains in the disordered or short-range ordered matrix. Changes in mechanical properties of cold-worked specimens produced by the low-temperature annealing process result from changes caused by two overlapping processes: the recovery and ordering processes. An analysis of observed changes in the mechanical properties in relation to reduction and annealing temperature and time was made.