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→Copper-Silver-(Cadmium) Alloys (Silver Bronze)
====<!--5.1.4.2-->Copper-Tin Alloys (Tin Bronze)====
Because of their good elastic spring properties and formability, the copper-tin alloys CuSn6 and CuSn8 are standard materials for spring contact elements in electromechanical components, such as connectors, switches and relays (<xr id="tab:Physical Properties of Copper-Tin Alloys"/><!--(Tab. 5.9)--> and <xr id="tab:Mechanical Properties of Copper-Tin Alloys"/><!--(Tab.5.10)-->). Besides these, other alloys such as CuSn4, CuSn5 and the multi-metal tin bronze CuSn3Zn9 have significant usage – mainly in North America. <!--5.10--><xr id="fig:Phase diagram of the Cu-Sn system for the range of 0 – 30 wt% Sn"/> shows the copper rich side of the phase diagram for the CuSn system. The mechanical property values achieved by cold forming are superior to these of the brass alloys (<xr id="fig:Mechanical properties of tin bronze depending on the tin content (cold working 0 and 50%)"/><!--(Fig. 5.11)-->). They increase significantly with increasing Sn content. The work hardening and softening behavior are shown for the example of CuSn8 in <xr id="fig:Strain hardening of CuSn8 by cold working"/><!--Figures 5.12--> and <xr id="fig:Softening of CuSn8 after 3 hrs annealing after 50% cold working"/><!--Fig. 5.13-->. The stress relaxation properties for CuSn alloys are good for up to 100°C, deteriorate however quickly for temperatures above 150°C.
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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 α -range which means that they are single-phase alloys (<xr id="fig:Copper rich region of the ternary copper-nickel-zinc phase diagram with indication of the more commonly available german silver materials"/><!--(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 <xr id="fig:Strain hardening of CuNi12Zn24 by cold working"/><!--Figures 5.15--> and <xr id="fig:Softening of CuNi12Zn24 after 3 hrs annealing after 50% cold working"/><!--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
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<figure id="fig:Copper rich region of the ternary copper-nickel-zinc phase diagram with indication of the more commonly available german silver materials">
[[File:Copper rich region of the termary copper nickel zinc phase diagram.jpg|right|thumb|Figure 10: Copper rich region of the ternary copper-nickel-zinc phase diagram with indication of the more commonly available german silver materials]]
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====<!--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 additional 1.5 wt% Cd. The phase diagram <xr id="fig:Phase diagram of copper-silver for the range of 0 – 40 wt% silver"/><!--(Fig. 5.17)--> shows, that in principle the CuAg alloys can be precipitation hardened, but the possible increase in mechanical strength is rather small.
Copper-silver alloys have good spring properties and compared to other spring materials have a high electrical conductivity (<xr id="tab:tab5.13"/> <!--(Tab. 5.13)--> and <xr id="tab:tab5.14"/><!--(Tab. 5.14)-->). The mechanical strength values in the strongly worked condition are comparable to those of the copper-tin alloys. Work hardening and softening behavior are shown for the example of CuAg2 [[#figures5|(Figs. 13 – 15)]]<!--(Figs. 5.18 – 5.20)-->. For the relaxation behavior, the silver bronzes are superior to German silver and tin bronze.
Because of their good spring properties combined with high electrical conductivity, silver bronzes are suitable for the use contact springs in relays
<sup>1)</sup> t: Strip thickness max. 0.5 mm
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