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Pure Gold is besides Platinum the chemically most stable of all precious metals. In its pure form it is not very suitable for use as a contact material in electromechanical devices because of its tendency to stick and cold-weld at even low contact forces. In addition it is not hard or strong enough to resist mechanical wear and exhibits high materials losses under electrical arcing loads <xr id="tab:tab2Contact_and_Switching_Properties_of_Gold_and_Gold_Alloys"/><!--(Tab. 2.4"/)-->. This limits its use in form of thin electroplated or vacuum deposited layers.
For most electrical contact applications gold alloys are used. Depending on the alloying metal the melting is performed either under in a reducing atmosphere or in a vacuum. The choice of alloying metals depends on the intended use of the resulting contact material. The binary Au alloys with typically <10 wt% of other precious metals such as Pt, Pd, or Ag or non-precious metals like Ni, Co, and Cu are the more commonly used ones <xr id="tab:tab2.2Physical_Properties_of_Gold_and_Gold_Alloys"/> ''<!--(Table Tab. 2.2)''-->.On one hand these alloy additions improve the mechanical strength and electrical switching properties but on the other hand reduce the electrical conductivity and chemical corrosion resistance <xr id="fig:fig2.2Influence_of_1_10_atomic_of_different"/>''<!--(Fig. 2.2)'' --> to varying degrees.
Under the aspect of reducing the gold content ternary alloys with a gold content of approximately 70 wt% and additions of Ag and Cu or Ag and Ni resp., for example AuAg25Cu5 or AuAg20Cu10 are used which exhibit for many applications good mechanical stability while at the same time have sufficientresistance against the formation of corrosion layers <xr id="tab:tab2.3Mechanical Properties of Gold and Gold-Alloys"/>''<!--(Table 2.3)''-->. '''Table 2.1: Commonly Used Grades of Gold'''
<figtable id="tab:Commonly Used Grades of Gold">
<caption>'''Commonly Used Grades of Gold<!--(2.1)-->'''</caption>
<table class="twocolortable">
<tr><th><p class="s11">Designation</p></th><th><p class="s11">Composition Au</p><p class="s11">(min. content)</p></th><th><p class="s11">Impurites ppm</p></th><th><p class="s12">Remarks on forms and application</p></th></tr><tr><td><p class="s11">Electronic Glod</p><p class="s11">Gold</p></td><td><p class="s11">99.999</p></td><td><p class="s11">Cu < 3</p><p class="s11">Ag < 3</p><p class="s11">Ca < 1</p><p class="s11">Mg <1</p><p class="s11">Fe < 1</p></td><td><p class="s12">Wires, strips, alloying metal for semiconductors, electronic components</p></td></tr><tr><td><p class="s11">Pure Gold</p></td><td><p class="s11">99.995</p></td><td><p class="s11">Cu < 10</p><p class="s11">Ag < 15</p><p class="s11">Ca < 20</p><p class="s11">Mg < 10</p><p class="s11">Fe < 3</p><p class="s11">Si < 10</p><p class="s11">Pb < 20</p></td><td><p class="s12">Granulate for high purity alloys, strips, tubing, profiles</p></td></tr><tr><td><p class="s11">Ingot Grade-Gold</p></td><td><p class="s11">99.95</p></td><td><p class="s11">Cu < 100</p><p class="s11">Ag < 150</p><p class="s11">Ca < 50</p><p class="s11">Mg < 50</p><p class="s11">Fe < 30</p><p class="s11">Si < 10</p></td><td><p class="s12">Alloys, commonly used grade</p></td></tr></table>
</figtable>
<div class="multiple-images">
<figtable id="tab:tab2.2Physical_Properties_of_Gold_and_Gold_Alloys">
[[File:Physical Properties of Gold and Gold-Alloys.jpg|left|thumb|<caption>Tab 2.2 Physical Properties of Gold and Gold-Alloys</caption>]]
</figtable>
<figure id="fig:fig2.2Influence_of_1_10_atomic_of_different">
[[File:Influence of 1-10 atomic of different.jpg|left|thumb|<caption>Fig 2.2 Influence of 1-10 atomic% of different alloying metals on the electrical resistivity of gold (according to J. O. Linde)</caption>]]
</figure>
<div class="clear"></div>
<figtable id="tab:tab2Mechanical Properties of Gold and Gold-Alloys"><caption>'''<!--Tab.2.3":-->Mechanical Properties of Gold and Gold-Alloys'''</caption>
{| class="twocolortable" style="text-align: left; font-size: 12px"
|-
</figtable>
Other ternary alloys based on the AuAg system are AuAg26Ni3 and AuAg25Pt6. These alloys are mechanically similar to the AuAgCu alloys but have significantly higher oxidation resistance at elevated temperatures <xr id="tab:tab2.4Contact_and_Switching_Properties_of_Gold_and_Gold_Alloys"/>''<!--(Table 2.4)''-->.
<figtable id="tab:tab2.4Contact_and_Switching_Properties_of_Gold_and_Gold_Alloys"><caption>'''<!--Table 2.4: -->Contact and Switching Properties of Gold and Gold Alloys'''</caption>
<table class="twocolortable">
<tr><th><p class="s11">Material</p></th><th><p class="s12">Properties<th colspan="2"></p></th></tr><tr><td><p class="s11">Au</p></td><td><p class="s12">Highest corrosion resistance, low</p><p class="s12">hardness</p></td><td><p class="s12">High electr. conductivity,</p><p class="s12">strong tendency to cold welding</p></td></tr><tr><td><p class="s11">AuAg8</p></td><td><p class="s12">High corrosion resistance, low thermo</p><p class="s12">e.m.f.</p></td><td><p class="s12">Low contact resistance</p></td></tr><tr><td><p class="s11">AuPt10</p><p class="s11">AuPd5</p></td><td><p class="s12">Very high corrosion resistance</p></td><td><p class="s12">High hardness</p></td></tr><tr><td><p class="s11">AuAg10 - 30</p></td><td><p class="s12">Mostly corrosion resistant</p></td><td><p class="s12">Higher hardness</p></td></tr><tr><td><p class="s11">AuNi5</p><p class="s11">AuCo5</p></td><td><p class="s12">High corrosion resistance, low</p><p class="s12">tendency to material transfer</p></td><td><p class="s12">High hardness</p></td></tr><tr><td><p class="s11">AuAg25Pt6</p></td><td><p class="s12">High corrosion resistance, low contact resistance</p></td><td><p class="s12">High hardness</p></td></tr><tr><td><p class="s11">AuAg26Ni3</p><p class="s11">AuAg25Cu5</p><p class="s11">AuAg20Cu10</p></td><td><p class="s12">Limited corrosion resistance</p></td><td><p class="s12">High hardness</p></td></tr><tr><td><p class="s11">AuPd40</p><p class="s11">AuPd35Ag10</p><p class="s11">AuCu14Pt9Ag4</p></td><td><p class="s12">High corrosion resistance</p></td><td><p class="s12">High hardness and mechanical</p><p class="s12">wear resistance</p></td></tr></table>
Gold alloys are used in the form of welded wire or profile (also called weldtapes), segments, contact rivets, and stampings produced from clad strip
materials. The selection of the bonding process is based on the cost for the joining process, and most importantly on the economical aspect of using theleast possible amount of the expensive precious metal component.
Besides being used as switching contacts in relays and pushbuttons, gold alloys are also applied in the design of connectors as well as sliding contacts for potentiometers, sensors, slip rings, and brushes in miniature DC motors <xr id="tab:tab2.5Application Examples and Forms of Gold and Gold Alloys"/>''<!--(Table 2.5)''-->.
<figtable id="tab:tab2.5Application Examples and Forms of Gold and Gold Alloys"><caption>'''<!--Table 2.5: -->Application Examples and Forms of Gold and Gold Alloys'''</caption>
<table class="twocolortable">
<xr id====Picture===="fig:Phase diagram of goldplatinum"/> Fig. 2.3: Phase diagram of goldplatinum
<xr id="fig:Phase diagram of gold-silver"/> Fig. 2.4: Phase diagram of gold-silver
<xr id="fig:Phase diagram of gold-copper"/> Fig. 2.5: Phase diagram of gold-copper
<xr id="fig:Phase diagram of gold-nickel"/> Fig. 2.6: Phase diagram of gold-nickel
<xr id="fig:Phase diagram of gold-cobalt"/> Fig. 2.7: Phase diagram of gold-cobalt
<xr id="fig:Strain hardening of Au by cold working"/> Fig. 2.8: Strain hardening of Au by cold working
<xr id="fig:Softening of Au after annealing for 0.5 hrs"/> Fig. 2.9: Softening of Au after annealing for 0.5 hrs after 80% cold working
<xr id="fig:Strain hardening of AuPt10 by cold working"/> Fig. 2.10: Strain hardening of AuPt10 by cold working
<xr id="fig:Strain hardening of AuAg20 by cold working"/> Fig. 2.11: Strain hardening of AuAg20 by cold working
<xr id="fig:Strain hardening of AuAg30 by cold working"/> Fig. 2.12: Strain hardening of AuAg30 by cold working
<xr id="fig:Strain hardening of AuNi5 by cold working"/> Fig. 2.13: Strain hardening of AuNi5 by cold working
<xr id="fig:Softening of AuNi5 after annealing for 0.5 hrs"/> Fig. 2.14: Softening of AuNi5 after annealing for 0.5 hrs after 80% cold working
<xr id="fig:Strain hardening of AuCo5 by cold working"/> Fig. 2.15: Strain hardening of AuCo5 by cold working
<xr id="fig:Precipitation hardening of AuCo5 at"/> Fig. 2.16: Precipitation hardening of AuCo5 at 400°C hardening temperature
<xr id="fig:Strain hardening of AuAg25Pt6 by cold working"/> Fig. 2.17: Strain hardening of AuAg25Pt6 by cold working
<xr id="fig:Strain hardening of AuAg26Ni3 by cold working"/> Fig. 2.18: Strain hardening of AuAg26Ni3 by cold working
<xr id="fig:Softening of AuAg26Ni3 after annealing for 0.5-hrs"/> Fig. 2.19: Softening of AuAg26Ni3 after annealing for 0.5 hrs after 80% cold working
<xr id="fig:Strain hardening of AuAg25Cu5 by cold working"/> Fig. 2.20: Strain hardening of AuAg25Cu5 by cold working
<xr id="fig:Strain hardening of AuAg20Cu10 by cold working"/> Fig. 2.21: Strain hardening of AuAg20Cu10 by cold working
<xr id="fig:Softening of AuAg20Cu10 after annealing for 0.5 hrs"/> Fig. 2.22: Softening of AuAg20Cu10 after annealing for 0.5 hrs after 80% cold working
<xr id="fig:Strain hardening of AuCu14Pt9Ag4 by cold working"/> Fig. 2.23: Strain hardening of AuCu14Pt9Ag4 by cold working
<xr id="fig:fig2.24Precipitation hardening of AuCu14Pt9Ag4"/> Fig. 2.24: Precipitation hardening of AuCu14Pt9Ag4 at different hardening temperatures after 50% cold working
<div class="multiple-images">
<figure id="fig:fig2.3Phase diagram of goldplatinum">
[[File:Phase diagram of goldplatinum.jpg|left|thumb|<caption>Phase diagram of goldplatinum</caption>]]
</figure>
<figure id="fig:fig2.4Phase diagram of gold-silver">
[[File:Phase diagram of gold-silver.jpg|left|thumb|<caption>Phase diagram of gold-silver</caption>]]
</figure>
<figure id="fig:fig2.5Phase diagram of gold-copper">
[[File:Phase diagram of gold-copper.jpg|left|thumb|<caption>Phase diagram of gold-copper</caption>]]
</figure>
<figure id="fig:fig2.6Phase diagram of gold-nickel">
[[File:Phase diagram of gold-nickel.jpg|left|thumb|<caption>Phase diagram of gold-nickel</caption>]]
</figure>
<figure id="fig:fig2.7Phase diagram of gold-cobalt">
[[File:Phase diagram of gold-cobalt.jpg|left|thumb|<caption>Phase diagram of gold-cobalt</caption>]]
</figure>
<figure id="fig:fig2.8Strain hardening of Au by cold working">
[[File:Strain hardening of Au by cold working.jpg|left|thumb|<caption>Strain hardening of Au by cold working</caption>]]
</figure>
<figure id="fig:fig2Softening of Au after annealing for 0.95 hrs">
[[File:Softening of Au after annealing for 0.5 hrs.jpg|left|thumb|<caption>Softening of Au after annealing for 0.5 hrs after 80% cold working</caption>]]
</figure>
<figure id="fig:fig2.10Strain hardening of AuPt10 by cold working">
[[File:Strain hardening of AuPt10 by cold working.jpg|left|thumb|<caption>Strain hardening of AuPt10 by cold working</caption>]]
</figure>
<figure id="fig:fig2.11Strain hardening of AuAg20 by cold working">
[[File:Strain hardening of AuAg20 by cold working.jpg|left|thumb|<caption>Strain hardening of AuAg20 by cold working</caption>]]
</figure>
<figure id="fig:fig2.12Strain hardening of AuAg30 by cold working">
[[File:Strain hardening of AuAg30 by cold working.jpg|left|thumb|<caption>Strain hardening of AuAg30 by cold working</caption>]]
</figure>
<figure id="fig:fig2.13Strain hardening of AuNi5 by cold working">
[[File:Strain hardening of AuNi5 by cold working.jpg|left|thumb|<caption>Strain hardening of AuNi5 by cold working</caption>]]
</figure>
<figure id="fig:fig2Softening of AuNi5 after annealing for 0.145 hrs">
[[File:Softening of AuNi5 after annealing for 0.5 hrs.jpg|left|thumb|<caption>Softening of AuNi5 after annealing for 0.5 hrs after 80% cold working</caption>]]
</figure>
<figure id="fig:fig2.15Strain hardening of AuCo5 by cold working">
[[File:Strain hardening of AuCo5 by cold working.jpg|left|thumb|<caption>Strain hardening of AuCo5 by cold working</caption>]]
</figure>
<figure id="fig:fig2.16Precipitation hardening of AuCo5 at">
[[File:Precipitation hardening of AuCo5 at.jpg|left|thumb|<caption>Precipitation hardening of AuCo5 at 400°C hardening temperature</caption>]]
</figure>
<figure id="fig:fig2.17Strain hardening of AuAg25Pt6 by cold working">
[[File:Strain hardening of AuAg25Pt6 by cold working.jpg|left|thumb|<caption>Strain hardening of AuAg25Pt6 by cold working</caption>]]
</figure>
<figure id="fig:fig2.18Strain hardening of AuAg26Ni3 by cold working">
[[File:Strain hardening of AuAg26Ni3 by cold working.jpg|left|thumb|<caption>Strain hardening of AuAg26Ni3 by cold working</caption>]]
</figure>
<figure id="fig:fig2Softening of AuAg26Ni3 after annealing for 0.195-hrs">
[[File:Softening of AuAg26Ni3 after annealing for 0.5-hrs.jpg|left|thumb|<caption>Softening of AuAg26Ni3 after annealing for 0.5 hrs after 80% cold working</caption>]]
</figure>
<figure id="fig:fig2.20Strain hardening of AuAg25Cu5 by cold working">
[[File:Strain hardening of AuAg25Cu5 by cold working.jpg|left|thumb|<caption>Strain hardening of AuAg25Cu5 by cold working</caption>]]
</figure>
<figure id="fig:fig2.21Strain hardening of AuAg20Cu10 by cold working">
[[File:Strain hardening of AuAg20Cu10 by cold working.jpg|left|thumb|<caption>Strain hardening of AuAg20Cu10 by cold working</caption>]]
</figure>
<figure id="fig:fig2Softening of AuAg20Cu10 after annealing for 0.225 hrs">
[[File:Softening of AuAg20Cu10 after annealing for 0.5 hrs.jpg|left|thumb|<caption>Softening of AuAg20Cu10 after annealing for 0.5 hrs after 80% cold working</caption>]]
</figure>
<figure id="fig:fig2.23Strain hardening of AuCu14Pt9Ag4 by cold working">
[[File:Strain hardening of AuCu14Pt9Ag4 by cold working.jpg|left|thumb|<caption>Strain hardening of AuCu14Pt9Ag4 by cold working</caption>]]
</figure>
<figure id="fig:fig2.24Precipitation hardening of AuCu14Pt9Ag4">
[[File:Precipitation hardening of AuCu14Pt9Ag4.jpg|left|thumb|<caption>Precipitation hardening of AuCu14Pt9Ag4 at different hardening temperatures after 50% cold working</caption>]]
</figure>
==References==
[[Contact Materials for Electrical Engineering#References|References]]
[[de:Werkstoffe_auf_Gold-Basis]]
