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For most electrical contact applications, gold alloys are used. Depending on the alloying metal, the melting is performed either under 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, Ag or non-precious metals like Ni, Co and Cu are the more commonly used ones (<xr id="tab:Physical Properties of Gold and Gold-Alloys"/>)<!--(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:Influence_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:tab2Mechanical Properties of Gold and Gold-Alloys"/>)<!--(Table 2.3)-->. <figtable id="tab:Commonly Used Grades of Gold"/><caption>'''Commonly Used Grades of Gold<!--(Table 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 Gold</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><br/><br/> <figtable id="tab:Physical Properties of Gold and Gold-Alloys"><caption>'''Physical Properties of Gold and Gold-Alloys'''</caption> {| class="twocolortable" style="text-align: left; font-size: 12px"|-!Material!Gold<br/>Content<br/>[wt.%]!Density<br/>[g/cm<sup>3</sup>]!Melting Point<br/>or Range<br/>[°C]!Electrical<br/>Resistivity<br/>[µΩ*cm]!Electrical<br/>Conductivity<br/>[MS/m]!Thermal<br/>Conductivity<br/>[W/(m*K)]!Temp. Coeff. of<br/>the electr. Resistance<br/>[10<sup>-3<sup/>/K]!Modulus of<br/>Elasticity<br/>[GPa]|-|Au (99,95)| >99,95|19,3|1064|2,32|43|317|4,0|79|-|AuAg8|92|18,1|1058|6,13|16,3|147|1,25|82|-|AuAg20|80|16,4|1035 - 1045|10,0|10|75|0,86|89|-|AuNi5|95|18,3|995 - 1018|13,5|7,4|53|0,71|83|-|AuCo5|95|18,2|1010 - 1015|55,6|1,8||0,68|88|-|AuCo5 (het.)|95|18,2|1010 - 1015|5,99|16,7||||-|AuAg25Cu5|70|15,2|950 - 980|12,2|8,2||0,75|89|-|AuAg20C10|70|15,1|865 - 895|13,3|7,5|66|0,52|87|-|AuAg26Ni3|71|15,4|990 - 1020|11,0|9,1|59|0,88|114|-|AuPt10|90|19,5|1150 - 1190|12,5|8,0|54|||-|AuAg25Pt6|69|16,1|1060|15,9|6,3|46|0,54|93|-|AuCu14Pt9Ag4|73|16,0|955|14,3 - 25|4 - 7||||-|}</figtable>
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<figtable id="tab:Mechanical Properties of Gold and Gold-Alloys"><caption>'''<!--Tab.2.3: -->Mechanical Properties of Gold and Gold-Alloys'''<figtable id="tab:tab2.3"/caption>
{| class="twocolortable" style="text-align: left; font-size: 12px"
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|}
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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:Contact_and_Switching_Properties_of_Gold_and_Gold_Alloys"/>)<!--(Table 2.4)-->. <figtable id="tab:Contact_and_Switching_Properties_of_Gold_and_Gold_Alloys"><caption>'''<!--Table 2.4: -->Contact and Switching Properties of Gold and Gold Alloys'''</caption><table border="1" cellspacing="0" styleclass="border-collapse:collapsetwocolortable"><tr><tdth><p class="s11">Material</p></tdth><tdth><p class="s12">Properties<th colspan="2"></p></tdth></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></figtable> Caused by higher gold prices over the past years , the development of alloys with further reduced gold content had a high priority. The starting point has been the AuPd system , which has continuous solubility of the two components. Besides the binary alloy of AuPd40 and the ternary one AuPd35Ag9 , other multiple component alloys were developed. These alloys typically have < 50 wt% Au and often can be solution hardened in order to obtain even higher hardness and tensile strength. They are mostly used in sliding contact applications. Gold alloys are used in the form of welded wire or profile (also called weldtapes), segments, contact rivets and stampings produced from clad stripmaterials. The selection of the bonding process is based on the cost for the joining process and most importantly on the economical aspect of using the least possible amount of the expensive precious metal component.
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<xr figure id="fig:fig2.4"/> Fig. 2.4: Phase diagram of gold-silver<figure id="fig:fig2.4">[[File:Phase diagram of gold-silver.jpg|rightleft|thumb|<caption>Phase diagram of gold-silver</caption>]]
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<xr figure id="fig:fig2.5"/> Fig. 2.5: Phase diagram of gold-copper<figure id="fig:fig2.5">[[File:Phase diagram of gold-copper.jpg|rightleft|thumb|<caption>Phase diagram of gold-copper</caption>]]
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<xr figure id="fig:fig2.6"/> Fig. 2.6: Phase diagram of gold-nickel<figure id="fig:fig2.6">[[File:Phase diagram of gold-nickel.jpg|rightleft|thumb|<caption>Phase diagram of gold-nickel</caption>]]
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<xr figure id="fig:fig2.7"/> Fig. 2.7: Phase diagram of gold-cobalt<figure id="fig:fig2.7">[[File:Phase diagram of gold-cobalt.jpg|rightleft|thumb|<caption>Phase diagram of gold-cobalt</caption>]]
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<xr figure id="fig:fig2.8"/> Fig. 2.8: Strain hardening of Au by cold working<figure id="fig:fig2.8">[[File:Strain hardening of Au by cold working.jpg|rightleft|thumb|<caption>Strain hardening of Au by cold working</caption>]]
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<xr figure id="fig:fig2.9"/> Fig. 2.9: Softening of Au after annealing for 0.5 hrs after 80% cold working<figure id="fig:fig2.9">[[File:Softening of Au after annealing for 0.5 hrs.jpg|rightleft|thumb|<caption>Softening of Au after annealing for 0.5 hrs after 80% cold working</caption>]]
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<xr figure id="fig:fig2.10"/> Fig. 2.10: Strain hardening of AuPt10 by cold working<figure id="fig:fig2.10">[[File:Strain hardening of AuPt10 by cold working.jpg|rightleft|thumb|<caption>Strain hardening of AuPt10 by cold working</caption>]]
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<xr figure id="fig:fig2.11"/> Fig. 2.11: Strain hardening of AuAg20 by cold working<figure id="fig:fig2.11">[[File:Strain hardening of AuAg20 by cold working.jpg|rightleft|thumb|<caption>Strain hardening of AuAg20 by cold working</caption>]]
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<xr figure id="fig:fig2.12"/> Fig. 2.12: Strain hardening of AuAg30 by cold working<figure id="fig:fig2.12">[[File:Strain hardening of AuAg30 by cold working.jpg|rightleft|thumb|<caption>Strain hardening of AuAg30 by cold working</caption>]]
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<xr figure id="fig:fig2.13"/> Fig. 2.13: Strain hardening of AuNi5 by cold working<figure id="fig:fig2.13">[[File:Strain hardening of AuNi5 by cold working.jpg|rightleft|thumb|<caption>Strain hardening of AuNi5 by cold working</caption>]]
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<xr figure id="fig:fig2.14"/> Fig. 2.14: Softening of AuNi5 after annealing for 0.5 hrs after 80% cold working<figure id="fig:fig2.14">[[File:Softening of AuNi5 after annealing for 0.5 hrs.jpg|rightleft|thumb|<caption>Softening of AuNi5 after annealing for 0.5 hrs after 80% cold working</caption>]]
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<xr figure id="fig:fig2.15"/> Fig. 2.15: Strain hardening of AuCo5 by cold working<figure id="fig:fig2.15">[[File:Strain hardening of AuCo5 by cold working.jpg|rightleft|thumb|<caption>Strain hardening of AuCo5 by cold working</caption>]]
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<xr figure id="fig:fig2.16"/> Fig. 2.16: Precipitation hardening of AuCo5 at 400°C hardening temperature<figure id="fig:fig2.16">[[File:Precipitation hardening of AuCo5 at.jpg|rightleft|thumb|<caption>Precipitation hardening of AuCo5 at 400°C hardening temperature</caption>]]
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<xr figure id="fig:fig2.17"/> Fig. 2.17: Strain hardening of AuAg25Pt6 by cold working<figure id="fig:fig2.17">[[File:Strain hardening of AuAg25Pt6 by cold working.jpg|rightleft|thumb|<caption>Strain hardening of AuAg25Pt6 by cold working</caption>]]
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<xr figure id="fig:fig2.18"/> Fig. 2.18: Strain hardening of AuAg26Ni3 by cold working<figure id="fig:fig2.18">[[File:Strain hardening of AuAg26Ni3 by cold working.jpg|rightleft|thumb|<caption>Strain hardening of AuAg26Ni3 by cold working</caption>]]
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<xr figure id="fig:fig2.19"/> Fig. 2.19: Softening of AuAg26Ni3 after annealing for 0.5 -hrs after 80% cold working<figure id="fig:fig2.19">[[File:Softening of AuAg26Ni3 after annealing for 0.5-hrs.jpg|rightleft|thumb|<caption>Softening of AuAg26Ni3 after annealing for 0.5 hrs after 80% cold working</caption>]]
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<xr figure id="fig:fig2.20"/> Fig. 2.20: Strain hardening of AuAg25Cu5 by cold working<figure id="fig:fig2.20">[[File:Strain hardening of AuAg25Cu5 by cold working.jpg|rightleft|thumb|<caption>Strain hardening of AuAg25Cu5 by cold working</caption>]]
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<xr figure id="fig:fig2.21"/> Fig. 2.21: Strain hardening of AuAg20Cu10 by cold working<figure id="fig:fig2.21">[[File:Strain hardening of AuAg20Cu10 by cold working.jpg|rightleft|thumb|<caption>Strain hardening of AuAg20Cu10 by cold working</caption>]]
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<xr figure id="fig:fig2.22"/> Fig. 2.22: Softening of AuAg20Cu10 after annealing for 0.5 hrs after 80% cold working<figure id="fig:fig2.22">[[File:Softening of AuAg20Cu10 after annealing for 0.5 hrs.jpg|rightleft|thumb|<caption>Softening of AuAg20Cu10 after annealing for 0.5 hrs after 80% cold working</caption>]]
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<xr figure id="fig:fig2.23"/> Fig. 2.23: Strain hardening of AuCu14Pt9Ag4 by cold working<figure id="fig:fig2.23">[[File:Strain hardening of AuCu14Pt9Ag4 by cold working.jpg|rightleft|thumb|<caption>Strain hardening of AuCu14Pt9Ag4 by cold working</caption>]]
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<xr figure id="fig:fig2.24"/> Fig. 2.24: Precipitation hardening of AuCu14Pt9Ag4 at different hardening temperatures after 50% cold working<figure id="fig:fig2.24">[[File:Precipitation hardening of AuCu14Pt9Ag4.jpg|rightleft|thumb|<caption>Precipitation hardening of AuCu14Pt9Ag4 at different hardening temperatures after 50% cold working</caption>]]
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==References==
[[Contact Materials for Electrical Engineering#References|References]]
[[de:Werkstoffe_auf_Gold-Basis]]