Changes

The high Cu content alloy materials are closest in their properties to pure copper materials. By defined addition of small amounts of alloying elements it is possible to increase the mechanical strength and especially the softening temperature of copper and at the same time decrease the electrical conductivity only insignificantly <xr id="fig:Influence of small additions on the electrical conductivity of copper"/> (Fig. 5.4). Silver, iron, tin, zinc, nickel, chromium, zirconium, silicon, and titanium are used. Usually the additive amounts are significantly below 3 wt%. This group of materials consists of mixed crystal as well as precipitation hardening alloys. The precipiytion hardening copper-beryllium and copper-chromium-zirconium materials are decribed later in a separate section.

From the large number of high-Cu alloys only the properties of selected ones are covered here ''(Tables 5.5 and 5.6)''. Some of these materials are not included in the EN standards system.

These newer copper based materials optimize properties such as electrical conductivity, mechanical strength, and relaxation, which are custom tailored to specific applications. Typical uses include contact springs for relays, switches, and connectors.

===5.1.4 Naturally Hard Copper Alloys===