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→5.1.4.1 Copper-Zinc Alloys (Brasses)
====5.1.4.1 Copper-Zinc Alloys (Brasses)====
Copper-zinc alloys are widely used as contact carrier materials in switching devices for electrical power engineering because of their high electrical conductivity, the higher mechanical strength combined with good formability compared to pure copper ''(Tables 5.7 and 5.8)'', and at the same time their reasonable economic costs. Especially suitable are the brasses with up to 37 wt% Zn content which are according to the phase diagram all made up from the " -phase of the CuZn system ''<xr id="fig:Phase diagram of copper-zinc for the range of 0-60 wt% zinc"/>(Fig. 5.5)''. It is important to note the strong dependence of the electrical conductivity and mechanical strength on the zinc content ''<xr id="fig:Mechanical properties of brass depending on the copper content (after cold working of 0 and 50%)"/>(Fig. 5.6)''.
The main disadvantages of these alloys are with increasing zinc content the also increasing tendency towards tension crack corrosion and the poorer stress relaxation properties compared to other copper alloys.
than the standard brass alloys. Even so this material is a naturally hardening alloy, a suitable heat treatment allows to further increase its strength.
<xr id="fig:Phase diagram of copper-zinc for the range of 0-60 wt% zinc"/> Fig. 5.5: Strain hardening of Ag 99.95 by cold working
<xr id="fig:Mechanical properties of brass depending on the copper content (after cold working of 0 and 50%)"/> Fig. 5.6: Mechanical properties of brass depending on the copper content (after cold working of 0 and 50%)
<xr id="fig:Strain hardening of CuZn36 by cold forming"/> Fig. 5.7: Strain hardening of CuZn36 by cold forming
<xr id="fig:Softening of CuZn36 after 3 hrs annealing after 25% cold working"/> Fig. 5.8: Softening of CuZn36 after 3 hrs annealing after 25% cold working
<div class="multiple-images">
<figure id="fig:Phase diagram of copper-zinc for the range of 0-60 wt% zinc">
Fig. 5.5: Phase diagram of copper-zinc for the range of 0-60 wt% zinc
[[File:Phase diagram of copper zinc.jpg|rightleft|thumb|Phase diagram of copper-zinc for the range of 0-60 wt% zinc]]</figure>
<figure id="fig:Mechanical properties of brass depending on the copper content (after cold working of 0 and 50%)">
Fig. 5.6: Mechanical properties of brass depending on the copper content (after cold working of 0 and 50%)
[[File:Mechanical properties of brass depending on the copper content.jpg|rightleft|thumb|Mechanical properties of brass depending on the copper content (after cold working of 0 and 50%)]]</figure>
<figure id="fig:Strain hardening of CuZn36 by cold forming">
Fig. 5.7: Strain hardening of CuZn36 by cold forming
[[File:Strain hardening of CuZn36 by cold forming.jpg|right|thumb|Strain hardening of CuZn36 by cold forming]]
</figure>
<figure id="fig:Softening of CuZn36 after 3 hrs annealing after 25% cold working">
Fig. 5.8: Softening of CuZn36 after 3 hrs annealing after 25% cold working
[[File:Softening of CuZn36 25.jpg|right|thumb|Softening of CuZn36 after 3 hrs annealing after 25% cold working]]
</figure>
</div>
<div class="clear"></div>
====5.1.4.2 Copper-Tin Alloys (Tin Bronze)====
