Precious Metal AuCo5
AuCo5 is a cobalt-hardened gold contact alloy — roughly 5 % cobalt in gold — that adds wear resistance while retaining gold's low, stable contact resistance.
Reference datasheet — AuCo5 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the H04 condition
AuCo5 tempers and conditions
AuCo5 is supplied in 4 conditions, soft to hard. H04 is the default FabDigit quotes; the values on this page are for it.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Pick for deep forming, riveting, cladding/bonding of contact buttons and for wire that must be bent tightly before hardening. | 130 | 330 | 30 | 95 HV | 13 % IACS |
Half hard | Compromise temper for formed contact clips that still need moderate bend forming after rolling or drawing. | 450 | 550 | 8 | 160 HV | 13.5 % IACS |
H04Default Full hard | Standard stock condition for contact springs, probe and connector wire needing high contact force retention and wear resistance. | 650 | 750 | 3 | 200 HV | 14 % IACS |
Cold worked + age hardened | Highest hardness and wear life for sliding/rotating contacts and slip rings; ageing precipitates Co and also lowers resistivity slightly. | 800 | 900 | 2 | 255 HV | 20 % IACS |
What is AuCo5?
AuCo5 is a cobalt-hardened gold contact alloy — roughly 5 % cobalt in gold — that adds wear resistance while retaining gold's low, stable contact resistance. It is used for low-level signal and connector contacts at 750 MPa tensile and 650 MPa yield strength, supplied as annealed to H04 strip, wire, rivets and as an inlay or clad layer on copper-alloy carrier strip. The constraints are 3 % elongation (formability score 25), 14 % IACS electrical conductivity, 65 W/m·K thermal conductivity, a 200 °C service ceiling and gold cost. Hard gold plating on a base-metal contact is the usual lower-cost substitute. AuCo5 has a density of 18.2 g/cm³ (0.658 lb/in³), heavier than 88% of precious metal grades. It melts at 996°C (1,825 °F). AuCo5 has a yield strength of 650 MPa (94.3 ksi) and a tensile strength of 750 MPa (109 ksi) — stronger than 99% of precious metal grades. Elongation at break is 3% and the elastic modulus is 95 GPa (13.8 Msi).
What is AuCo5 used for?
- telecom relay contacts
- connector plating substitutes
- low-current signal switches
- precision instrument contacts
Advantages
- High strength — 650 MPa (94.3 ksi), better than 99% of precious metal grades
- Polishes to a fine finish — 95/100, better than 86% of precious metal grades
Limitations
- Limited ductility — 3%, worse than 95% of precious metal grades
- Limited formability — 25/100, worse than 95% of precious metal grades
- Limited service temperature — 200°C (392 °F), worse than 89% of precious metal grades
- Heavy — 18.2 g/cm³ (0.658 lb/in³), worse than 88% of precious metal grades
- High embodied carbon — 12,000 kg CO₂/kg, worse than 76% of precious metal grades
AuCo5 properties
Typical room-temperature values for AuCo5-H04; bars are the position among precious metal grades.
Physical3
AuCo5 has a density of 18.2 g/cm³ (0.658 lb/in³), heavier than 88% of precious metal grades. It melts at 996°C (1,825 °F).
Mechanical10
AuCo5 has a yield strength of 650 MPa (94.3 ksi) and a tensile strength of 750 MPa (109 ksi) — stronger than 99% of precious metal grades. Elongation at break is 3% and the elastic modulus is 95 GPa (13.8 Msi).
Thermal6
AuCo5 is rated for continuous service to 200°C (392 °F). It conducts heat at 65 W/m·K (37.6 BTU/hr·ft·°F), worse than 67% of precious metal grades. Thermal expansion is 14.3 µm/m·K (7.94 µin/in·°F).
Electrical3
AuCo5 conducts electricity at 14 % IACS, worse than 70% of precious metal grades.
Chemical & Environmental3
Corrosion resistance is excellent (92/100), better than 73% of precious metal grades.
Sustainability4
Producing a kilogram of AuCo5 takes about 180,000 MJ of energy and emits 12,000 kg of CO₂ — more than 77% of precious metal grades. Typical recycled content is 35%.
Manufacturability8
AuCo5's machinability is fair (45/100, better than 59% of precious metal grades); weldability very good (70/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the precious metal family
Yield strength against density for every precious metal grade FabDigit runs. AuCo5 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with AuCo5
Is AuCo5 easy to machine?
Turns and slits like soft gold — gummy and prone to smearing; use polished carbide/diamond tools, high speed, light feeds, and capture all chips for refining.
Can AuCo5 be welded?
Resistance, percussion and laser welding of contact tips/rivets to Cu, CuBe or Ni substrates is standard; avoid fusion welding large sections to prevent Co-rich segregation.
Can AuCo5 be formed, bent or molded?
Excellent cold formability when annealed (rolling, drawing, stamping, cladding onto Cu alloy strip); intermediate anneals near 600–700 °C in inert/reducing atmosphere, then final cold work or age hardening.
AuCo5 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Cohardening addition; partly in solid solution, partly as fine precipitate | 4.5 – 5.5 | 5 |
| Nioptional grain refiner / incidental | 0 – 0.2 | |
| other, eachFe, Cu, Ag impurities | 0 – 0.05 | |
| Au≈95 wt % (about 2280 fine equivalent) | balance |
What surface finishes work on AuCo5?
Cannot be anodized; barrel- or wheel-polishes to a mirror finish, is often used as an inlay/clad layer, and needs no protective coating since the surface stays oxide- and sulfide-free.
Equivalent designations
Standards and trade names that resolve to Precious Metal AuCo5 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- Au-5Co
How much does AuCo5 cost?
AuCo5 is a high-cost precious metal ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
AuCo5 — frequently asked
What is AuCo5 used for?
AuCo5 is typically used for telecom relay contacts, connector plating substitutes, low-current signal switches and precision instrument contacts. In short: hard gold contact alloy; stable low contact resistance; wear-resistant versus pure gold.
What is the yield strength of AuCo5?
AuCo5 has a typical yield strength of 650 MPa (94.3 ksi) and a tensile strength of 750 MPa (109 ksi) — stronger than 99% of precious metal grades. Strength varies by condition: see the 4 listed tempers.
Is AuCo5 easy to machine?
Reasonably — machinability is rated fair (45/100, better than 59% of precious metal grades). Turns and slits like soft gold — gummy and prone to smearing; use polished carbide/diamond tools, high speed, light feeds, and capture all chips for refining.
Can AuCo5 be welded?
Yes — weldability is rated very good (70/100). Resistance, percussion and laser welding of contact tips/rivets to Cu, CuBe or Ni substrates is standard; avoid fusion welding large sections to prevent Co-rich segregation.
What surface finishes work on AuCo5?
Cannot be anodized; barrel- or wheel-polishes to a mirror finish, is often used as an inlay/clad layer, and needs no protective coating since the surface stays oxide- and sulfide-free.
Can AuCo5 be formed, bent or molded?
Excellent cold formability when annealed (rolling, drawing, stamping, cladding onto Cu alloy strip); intermediate anneals near 600–700 °C in inert/reducing atmosphere, then final cold work or age hardening.
What is the maximum service temperature of AuCo5?
AuCo5 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between AuCo5-H04 and AuCo5-O?
H04 is the default condition — standard stock condition for contact springs, probe and connector wire needing high contact force retention and wear resistance. O: pick for deep forming, riveting, cladding/bonding of contact buttons and for wire that must be bent tightly before hardening. Yield strength is 650 MPa in H04 versus 130 MPa in O.
How much does AuCo5 cost?
AuCo5 is a high-cost precious metal ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASM Handbook, Vol. 2: Properties and Selection — Nonferrous Alloys and Special-Purpose Materials (precious metals and electrical contact materials) — ASM International (1990)
- ASM Alloy Phase Diagrams Database — Au-Co system — ASM International (2016)
- Electrical Contacts: Principles and Applications (contact materials for low-level signal contacts) — CRC Press (2013)
- Precious-metal contact wire, strip and clad material data (Deringer-Ney / Materion class products) — producer datasheets (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.