A new high-strength (UTS:$90kg/mm^2$) and high-stiffness ($K_b:70kg/mm^2$) Cu-base alloy, comparable to a Cu-Be alloy (CDA 175), has been developed. The nominal composition of the alloy was Cu-22.7Zn-3.4A1-1.0Ni-0.3Si-0.1Zr, which was named as "PMC-707". The high strength coupled with good ductility was obtained mainly by grain size refinement by adding Si and Zr to Cu-22.7Zn-3.4Al-1.0Ni base.
It was found that the application of low-temperature annealing (150~ 230°C) on the cold-rolled plates resulted in the increase of hardness and the decrease of electrical resistivity with aging time. The increase of the hardness was due to the locking of dislocations by the solute atmosphere, while the electrical resistivity decreased primarily by the reduced stress fields caused by the decrease in point defect density at the elevated temperature exposure.
The apparent activation energy based on the variations of hardness and resistivity with aging time in the alloy was about 144 KJ/mole, which was about equal to the reported activation energy of the Zn diffusion in $\alpha$-brass, 180 KJ/mole.
In order to investigate the interaction between dislocation and solute atoms, dynamic strain aging behavior was examined on the recrystallized condition with varying test temperatures(-196~400°C). The apparent activation energy forming the jerky flow was about 0.46 eV, which was about equal to the reported activation energy of vacancy migration in $\alpha$-brass. The result indicated that the vacancy diffusion around dislocations played an important role in the dynamic strain aging behavior.
Dynamic strain aging behavior was also studied by the strain rate sensitivity. The strain rate sensitivity became negative at the critical strain for jerky flow.
In contrast to interstitial alloy, the total elongation did not decreased in this substitutional alloy at the temperatures dynamic strain aging occured.
