Changes

Because of their good elastic spring properties and formability the copper-tin alloys CuSn6 and CuSn8 are standard materials for spring contact elements in electrome-chanical components such as connectors, switches, and relays <xr id="tab:tab5.9"/> (Tab. 5.9) and <xr id="tab:tab5.10"/>(Tab.5.10). Besides these other alloys such as CuSn4 and CuSn5 and the multi-metal tin bronze CuSn3Zn9 have significant usage – mainly in North America.

Figure 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"/> 5.13. The stress relaxation properties for CuSn alloys are good for up to 100°C, deteriorate however quickly for temperatures above 150°C.