Svetlana Nestorovic

Influence of alloying and secondary annealing on anneal hardening effect at sintered copper alloys

This paper reports results of investigation carried out on sintered copper alloys (Cu, 8 at%; Zn, Ni, Al and Cu-Au with 4 at%Au). The alloys were subjected to cold rolling (30, 50 and 70%) and annealed isochronally up to recrystallization temperature. Changes in hardness and electrical conductivity were followed in order to investigate the anneal hardening effect. This effect was observed after secondary annealing also. Au and Al have been found to be more effective in inducing anneal hardening effect.

Influence of degree of deformation in rolling on anneal hardening effect of a cast copper alloy

This paper reports results of investigations carried out on a cast copper alloy containing 8 at.% Al. The alloy, and pure copper for the sake of comparison, were subjected to cold rolling with a final reduction of 30, 50 or 70%.The cold rolled copper and copper alloy samples were isochronally and isothermally annealed up to the recrystallization temperature. The hardness, strength and electrical conductivity were measured and X-ray and DSC analyses performed.Anneal hardening effect was observed in the alloy in the temperature range 180–300°C, followed by an increase in the electrical conductivity. The amount of strengthening increases with increasing degree of prior cold work. The X-ray analysis shows a change in the lattice parameter during annealing when anneal hardening effect was observed. The DSC analysis shows the exothermic character of this effect.

Properties improvement and microstructure changes during thermomechanical treatment in sintered Cu–Au alloy

Abstract The changes in hardness, microhardness, electrical conductivity and microstructure of the sintered Cu–4%Au (mole fraction) alloy during thermomechanical treatment were studied. Following the primary strain hardening, an annealing of rolled alloy in the temperature range of 60–350 °C provided additional strengthening due to the anneal hardening effect. An increase in properties took place in two stages, and the best combination of properties was achieved in the alloy pre-rolled with 40% reduction after annealing at 260 °C. Significant microstructural changes followed the changes of properties in the course of the thermomechanical treatment.

Influence of time of annealing on anneal hardening effect of a cast CuZn alloy

Investigated cast copper alloy containing 8at%Zn of a solute. For comparison parallel specimens made from cast pure copper. Copper and copper alloy were subjected to cold rolling with different a final reduction of 30,50 and 70%. The cold rolled copper and copper alloy samples were isochronally and isothermally annealed up to recrystallization temperature. After that the values of hardness, strength and electrical conductivity were measured and X-ray analysis was performed. These investigations show that anneal hardening effect at alloys was attained under recrystallization temperature in the temperature range of 180-3000C, followed with an increase in hardness. The amount of strengthening increase with increasing degree of prior cold work. Also the X-ray analysis show the change of lattice parameter during annealing when anneal hardening effect was attained.

Effect of deformation and oxygen content on mechanical properties of different copper wires

Investigations were done at dip-forming, contirod and SCR copper wire rods. These continuously cast and hot rolled copper wire rods (8 mm in diameter) were cold drawn in two drawing programmes (soft and hard drawn) to various diameters without any intermediate annealing. The results of influence of deformation and oxygen content on the flow stress, tensile elongation and number of twist to failure are given. Strength and strain hardening rates of hard-drawn wires always were higher than the soft-drawn wires. Oxygen effect on the ductility of copper wires measured with the tensile elongation and the number of twist to failure is not clear at large drawing prestrains.