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Created page with "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 d..."
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. 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 ''(Table 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 (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 sufficient
resistance against the formation of corrosion layers ''(Table 2.3)''. 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 ''(Table 2.4)''.
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 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 the
least 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
''(Table 2.5)''.
Table 2.3: Mechanical Properties of Gold and Gold-Alloys
Table 2.1: Commonly Used Grades of Gold
Table 2.2: Physical Properties of Gold and Gold-Alloys
Fig. 2.2:
Influence of 1-10 atomic% of different
alloying metals on the electrical resistivity of gold
(according to J. O. Linde)
Fig. 2.3:
Phase diagram
of goldplatinum
Fig. 2.4:
Phase diagram
of gold-silver
Fig. 2.5:
Phase diagram
of gold-copper
Fig. 2.6: Phase diagram of gold-nickel
Fig. 2.7: Phase diagram of gold-cobalt
Fig. 2.8:
Strain hardening
of Au by cold working
Fig. 2.9:
Softening of Au after annealing
for 0.5 hrs after 80%
cold working
Fig. 2.10:
Strain hardening of
AuPt10 by cold working
Fig. 2.11:
Strain hardening
of AuAg20 by cold working
Fig. 2.12:
Strain hardening of
AuAg30 by cold working
Fig. 2.13:
Strain hardening of AuNi5
by cold working
Fig. 2.14:
Softening
of AuNi5 after annealing
for 0.5 hrs after 80%
cold working
Fig. 2.15:
Strain hardening
of AuCo5 by cold working
Fig. 2.16:
Precipitation hardening of
AuCo5 at 400°C hardening
temperature
Fig. 2.17:
Strain hardening
of AuAg25Pt6 by cold working
Fig. 2.18:
Strain hardening
of AuAg26Ni3 by cold working
Fig. 2.19:
Softening
of AuAg26Ni3 after
annealing for 0.5 hrs
after 80% cold
working
Fig. 2.20:
Strain hardening of
AuAg25Cu5
by cold working
Fig. 2.21:
Strain hardening of
AuAg20Cu10
by cold working
Fig. 2.22:
Softening
of AuAg20Cu10 after
annealing for 0.5 hrs
after 80% cold working
Fig. 2.23:
Strain hardening of
AuCu14Pt9Ag4
by cold working
Fig. 2.24:
Precipitation
hardening of
AuCu14Pt9Ag4
at different
hardening
temperatures
after 50%
cold working
Table 2.4: Contact and Switching Properties of Gold and Gold Alloys
Table 2.5: Application Examples and Forms of Gold and Gold Alloys
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. 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 ''(Table 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 (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 sufficient
resistance against the formation of corrosion layers ''(Table 2.3)''. 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 ''(Table 2.4)''.
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 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 the
least 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
''(Table 2.5)''.
Table 2.3: Mechanical Properties of Gold and Gold-Alloys
Table 2.1: Commonly Used Grades of Gold
Table 2.2: Physical Properties of Gold and Gold-Alloys
Fig. 2.2:
Influence of 1-10 atomic% of different
alloying metals on the electrical resistivity of gold
(according to J. O. Linde)
Fig. 2.3:
Phase diagram
of goldplatinum
Fig. 2.4:
Phase diagram
of gold-silver
Fig. 2.5:
Phase diagram
of gold-copper
Fig. 2.6: Phase diagram of gold-nickel
Fig. 2.7: Phase diagram of gold-cobalt
Fig. 2.8:
Strain hardening
of Au by cold working
Fig. 2.9:
Softening of Au after annealing
for 0.5 hrs after 80%
cold working
Fig. 2.10:
Strain hardening of
AuPt10 by cold working
Fig. 2.11:
Strain hardening
of AuAg20 by cold working
Fig. 2.12:
Strain hardening of
AuAg30 by cold working
Fig. 2.13:
Strain hardening of AuNi5
by cold working
Fig. 2.14:
Softening
of AuNi5 after annealing
for 0.5 hrs after 80%
cold working
Fig. 2.15:
Strain hardening
of AuCo5 by cold working
Fig. 2.16:
Precipitation hardening of
AuCo5 at 400°C hardening
temperature
Fig. 2.17:
Strain hardening
of AuAg25Pt6 by cold working
Fig. 2.18:
Strain hardening
of AuAg26Ni3 by cold working
Fig. 2.19:
Softening
of AuAg26Ni3 after
annealing for 0.5 hrs
after 80% cold
working
Fig. 2.20:
Strain hardening of
AuAg25Cu5
by cold working
Fig. 2.21:
Strain hardening of
AuAg20Cu10
by cold working
Fig. 2.22:
Softening
of AuAg20Cu10 after
annealing for 0.5 hrs
after 80% cold working
Fig. 2.23:
Strain hardening of
AuCu14Pt9Ag4
by cold working
Fig. 2.24:
Precipitation
hardening of
AuCu14Pt9Ag4
at different
hardening
temperatures
after 50%
cold working
Table 2.4: Contact and Switching Properties of Gold and Gold Alloys
Table 2.5: Application Examples and Forms of Gold and Gold Alloys