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→5.1.4.3 Copper-Nickel-Zinc Alloys (German Silver)
Despite its lower electrical conductivity, the good spring properties, high corrosion resistance, and the good workability make copper-nickel-zinc alloys a frequently used spring contact carrier in switches and relays. As illustrated in the phase diagram the most commonly used materials are in the " -range which means that they are single-phase alloys ''(Fig. 5.14)''. The formability and strength properties of german silver are comparable to those of the copper-tin alloys. The work hardening and softening behavior is illustrated on the example of CuNi12Zn24 in Figures 5.15 and 5.16.
The relaxation behavior of Cu-Ni-Zn alloys is superior to the one for the tin bronzes. Additional advantages are the very good weldability, brazing
properties, and the high corrosion resistance of these copper-nickel-zinc alloys.
Fig. 5.14: Copper rich region of the ternary copper-nickel-zinc phase diagram with indication of the more commonly available german silver materials
Table 5.11: Physical Properties of Copper-Nickel-Zinc Alloys (2 teile!)
Table 5.12: Mechanical Properties of Copper-Nickel-Zinc Alloys (2 teile!)
Fig. 5.15: Strain hardening of CuNi12Zn24 by cold working
Fig. 5.16: Softening of CuNi12Zn24 after 3 hrs annealing after 50% cold working
=====5.1.4.4 Copper-Silver-(Cadmium) Alloys (Silver Bronze)=====
Besides the low-allowed CuAg0.1 other copper materials with higher silver contents (2-6 wt%) are also used as contacts carrier materials. Some of them contain additionally 1.5 wt% Cd. The phase diagram (Fig. 5.17) shows that in principle the CuAg alloys can be precipitation hardened, but the possible increase in mechanical strength is rather small.