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 precipitation 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 (<xr id="tab:Physical Properties of Selected High Cu Content Copper Alloys"/><!--(Tab. 5.5)--> and <xr id="tab:Mechanical Properties of Selected High Cu Content Copper Alloys"/><!--(Tab. 5.6)-->). Some of these materials are not included in the EN standards system.

The low alloyed materials CuAg0.1 and CuCd1 are mostly used as overhead drive cables , where they have to meet sustained loads at elevated temperatures without softening.

The materials CuFe0.1 and CuSn0.15 have a high electrical conductivity. The mechanical strength of both is relatively low but stays almost constant at temperatures up to 400°C. The They are used as substrates for power semiconductors and also as carriers for stationary contacts in higher energy switchgear.

CuFe2 is a material exhibiting high electrical conductivity and good formability. During an annealing process , Fe-rich precipitations are formed in the " -Cu matrix , which change changes the mechanical properties very little but increase increases the electrical conductivity significantly. Besides being used as a contact carrier material in switching devices, this material has broader applications in automotive connectors and as a substrate in the semiconductor technology.

CuNi2Si has high mechanical strength, good formability, and at the same time high electrical conductivity. This combination of advantageous properties is achieved by a defined finely dispersed precipitation of nickel silicides. CuNi2Si is used mainly in the form of stamped and formed parts in thermally stressed electromechanical components for automotive applications.

Alloys like brasses (CuZn), tin bronzes (CuSN), and German silver (CuNiZn), for which the required hardness is achieved by cold working, are defined as naturally hard alloys. Included in this group are also the silver bronzes (CuAg) with 2 – 6 wt% of Ag.

Besides the naturally hard copper materials , precipitation hardening, copper alloys play also an important role as carrier materials for electrical contacts. By means of a suitable heat treatment, finely dispersed precipitations of a second phase can be achieved, which increases the mechanical strength of these copper alloys significantly.

For spring contact components , the interdependent relations between electrical conductivity and fatigue strength, or electrical conductivity and relaxation behavior are of main importance. The first case is critical for higher load relay springs. CuAg2 plays an important role for these applications. The latter is critical for components that are exposed to continuing high mechanical stresses like for example in connectors. The spring force must stay close to constant over the expected life time of the parts, even at elevated temperatures from the environment or current carrying. In this case , the relaxation behavior of the copper materials, which may cause a decrease in spring force over time, must be considered. Besides this , easy forming during manufacturing must be possible; this means , that bending operations can also be performed at high mechanical strength values.

The increasing requirements on spring components in connectors, especially for use in automotive applications, such as higher surrounding temperatures, increased reliability, and the trend towards miniaturization led to a change of materials from traditionally CuZn30 and CuSn4 to CuNiSi alloys, for example. These CuNiSi alloys and the newer heavy duty copper alloys like CuNi1Co1 , are significantly improved with regards to mechanical strength, relaxation behavior and electrical conductivity.

Technical grade pure nickel commonly contains 99.0 to 99.8 wt% Ni and up to 1 wt% Co. Other ingredients are iron and manganese (<xr id="tab:Physical Properties of Nickel and Nickel Alloys"/><!--(Tab. 5.21)--> and <xr id="tab:Mechanical Properties of Nickel and Nickel Alloys"/><!--(Tab. 5.22)-->). Work hardening and softening behavior of nickel are shown in [[#figures11|(Figs. 5 – 6)]]<!--Figs. 5.45 and 5.46-->.

[[File:Strain hardening of technical pure nickel by cold working.jpg|right|thumb|Figure 5: Strain hardening of technical pure nickel by cold working]]

[[File:Softening of technical grad nickel after annealing for 3 hrs.jpg|right|thumb|Figure 6: Softening of technical grad nickel after annealing for 3 hrs after 50% cold working]]