Precious Metal AuCo5-O (Annealed)
Temper
Pick for deep forming, riveting, cladding/bonding of contact buttons and for wire that must be bent tightly before hardening.
Values for the O condition
Other AuCo5 tempers and conditions
AuCo5 is listed in 4 conditions; see the grade overview at AuCo5.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
OThis page 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-O?
AuCo5-O is AuCo5 in the O temper — pick for deep forming, riveting, cladding/bonding of contact buttons and for wire that must be bent tightly before hardening. AuCo5-O has a yield strength of 130 MPa (18.9 ksi) and a tensile strength of 330 MPa (47.9 ksi) — weaker than 72% of precious metal grades. Elongation at break is 30% and the elastic modulus is 95 GPa (13.8 Msi). AuCo5-O 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). H04 is the default condition FabDigit quotes; O is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 95/100, better than 86% of precious metal grades
Limitations
- 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-O properties
Typical room-temperature values for AuCo5-O; 12 are specific to this condition. Other listed values are AuCo5 reference data and may not represent this condition. Bars are the position among precious metal grades.
Physical3
AuCo5-O 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-O has a yield strength of 130 MPa (18.9 ksi) and a tensile strength of 330 MPa (47.9 ksi) — weaker than 72% of precious metal grades. Elongation at break is 30% and the elastic modulus is 95 GPa (13.8 Msi).
Thermal6
AuCo5-O is rated for continuous service to 400°C (752 °F). It conducts heat at 60 W/m·K (34.7 BTU/hr·ft·°F), worse than 72% of precious metal grades. Thermal expansion is 14.3 µm/m·K (7.94 µin/in·°F).
Electrical3
AuCo5-O conducts electricity at 13 % IACS, worse than 72% 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-O 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-O's machinability is fair (35/100, worse than 73% of precious metal grades); weldability very good (70/100); formability very good (80/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with AuCo5-O
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.
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.
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 | — |
AuCo5-O — frequently asked
What is AuCo5-O used for?
AuCo5-O 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-O?
AuCo5-O has a typical yield strength of 130 MPa (18.9 ksi) and a tensile strength of 330 MPa (47.9 ksi) — weaker than 72% of precious metal grades. Strength varies by condition: see the 4 listed tempers.
Is AuCo5-O easy to machine?
Not especially — machinability is rated fair (35/100, worse than 73% 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-O 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-O?
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-O 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-O?
AuCo5-O is rated for continuous use to about 400°C (752 °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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.