Tungsten Alloy 90W-7Ni-3Cu-SR (Stress relieved)
Heat-treated state
ASTM B777 Class 1
Choose for thin-walled or tightly toleranced machined parts where residual stress would cause distortion.
Values for the SR condition
Other 90W-7Ni-3Cu tempers and conditions
90W-7Ni-3Cu is listed in 3 conditions; see the grade overview at 90W-7Ni-3Cu.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
SRThis page Stress relieved | Choose for thin-walled or tightly toleranced machined parts where residual stress would cause distortion. | 520 | 690 | 4 | 25 HRC | 15 % IACS |
Sintered plus vacuum/hydrogen anneal and rapid cool | Pick when maximum ductility and impact resistance are required, e.g. dynamic counterweights or parts that see handling shock. | 560 | 740 | 6 | 26 HRC | 15 % IACS |
Cold worked | Only for small-diameter rod/wire where higher strength and stiffness matter more than ductility; reductions are much smaller than for W-Ni-Fe grades. | 800 | 900 | 1.5 | 34 HRC | 14 % IACS |
What is 90W-7Ni-3Cu-SR?
90W-7Ni-3Cu-SR is 90W-7Ni-3Cu heat treated to SR — choose for thin-walled or tightly toleranced machined parts where residual stress would cause distortion. 90W-7Ni-3Cu-SR has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 690 MPa (100 ksi) — weaker than 89% of tungsten alloy grades. Elongation at break is 4% and the elastic modulus is 320 GPa (46.4 Msi). 90W-7Ni-3Cu-SR has a density of 17 g/cm³ (0.614 lb/in³), lighter than 74% of tungsten alloy grades. It melts at 1,400°C (2,552 °F).
Advantages
- Easy to machine — 43/100, better than 105% of tungsten alloy grades
- Tough — resists crack growth — 42 MPa·√m (38.2 ksi·√in), better than 90% of tungsten alloy grades
- Low embodied carbon — 21 kg CO₂/kg, better than 86% of tungsten alloy grades
- Ductile — tolerates forming and impact — 4%, better than 80% of tungsten alloy grades
Limitations
- Limited service temperature — 400°C (752 °F), worse than 98% of tungsten alloy grades
- Hard to polish — 55/100, worse than 98% of tungsten alloy grades
- Low stiffness — 320 GPa (46.4 Msi), worse than 90% of tungsten alloy grades
- Low strength — 520 MPa (75.4 ksi), worse than 89% of tungsten alloy grades
- Needs corrosion protection — 45/100, worse than 86% of tungsten alloy grades
90W-7Ni-3Cu-SR properties
Typical room-temperature values for 90W-7Ni-3Cu-SR; 23 are specific to this condition. Other listed values are 90W-7Ni-3Cu reference data and may not represent this condition. Bars are the position among tungsten alloy grades.
Physical2
90W-7Ni-3Cu-SR has a density of 17 g/cm³ (0.614 lb/in³), lighter than 74% of tungsten alloy grades. It melts at 1,400°C (2,552 °F).
Mechanical16
90W-7Ni-3Cu-SR has a yield strength of 520 MPa (75.4 ksi) and a tensile strength of 690 MPa (100 ksi) — weaker than 89% of tungsten alloy grades. Elongation at break is 4% and the elastic modulus is 320 GPa (46.4 Msi).
Thermal5
90W-7Ni-3Cu-SR is rated for continuous service to 400°C (752 °F). It conducts heat at 95 W/m·K (54.9 BTU/hr·ft·°F), worse than 71% of tungsten alloy grades. Thermal expansion is 5.2 µm/m·K (2.89 µin/in·°F).
Electrical3
90W-7Ni-3Cu-SR conducts electricity at 15 % IACS, worse than 69% of tungsten alloy grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 86% of tungsten alloy grades.
Sustainability4
Producing a kilogram of 90W-7Ni-3Cu-SR takes about 300 MJ of energy and emits 21 kg of CO₂ — less than 88% of tungsten alloy grades. Typical recycled content is 25%.
Manufacturability7
90W-7Ni-3Cu-SR's machinability is fair (43/100, better than 105% of tungsten alloy grades); weldability not recommended (12/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 90W-7Ni-3Cu-SR
Is 90W-7Ni-3Cu easy to machine?
Turn/mill with rigid setups, sharp negative-rake carbide (or CBN for finishing), low speed and heavy flood coolant; the material is abrasive and chips are short and brittle — avoid interrupted cuts on thin sections.
Can 90W-7Ni-3Cu be welded?
Fusion welding cracks and coarsens the tungsten skeleton — join by Ag-Cu brazing, electron-beam/inertia welding with qualified procedures, or by screws, pins and shrink fits.
Can 90W-7Ni-3Cu be formed, bent or molded?
Made only by press-and-sinter (liquid-phase sintering at ~1400–1500 °C); the W-Ni-Cu matrix tolerates very little cold work, so near-net pressing plus machining is the normal route.
What surface finishes work on 90W-7Ni-3Cu?
Grind/lap for tight tolerances; electroless or electrolytic nickel plating (5–20 µm) is standard for corrosion protection and to prevent staining on handled shielding parts.
90W-7Ni-3Cu 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 |
|---|---|---|
| WASTM B777 Class 1 nominal 90 wt% tungsten | 89 – 91 | 90 |
| Nimatrix former, Ni:Cu ≈ 7:3 | 6.3 – 7.7 | 7 |
| Cukeeps the binder non-magnetic | 2.7 – 3.3 | 3 |
| Feimpurity limit; Fe would make the matrix magnetic | ≤ 0.2 | — |
| Other (each)C, O, Si, Ca impurities | ≤ 0.1 | — |
| Ni+Cu matrixbalance to 100 wt% | balance | — |
90W-7Ni-3Cu-SR — frequently asked
What is 90W-7Ni-3Cu-SR used for?
90W-7Ni-3Cu-SR is typically used for radiation shielding, collimators, counterweights and vibration damping masses. In short: very high density metal; machinable tungsten heavy alloy; lead-free shielding material.
What is the yield strength of 90W-7Ni-3Cu-SR?
90W-7Ni-3Cu-SR has a typical yield strength of 520 MPa (75.4 ksi) and a tensile strength of 690 MPa (100 ksi) — weaker than 89% of tungsten alloy grades. Strength varies by condition: see the 3 listed tempers.
Is 90W-7Ni-3Cu-SR easy to machine?
Not especially — machinability is rated fair (43/100, better than 105% of tungsten alloy grades). Turn/mill with rigid setups, sharp negative-rake carbide (or CBN for finishing), low speed and heavy flood coolant; the material is abrasive and chips are short and brittle — avoid interrupted cuts on thin sections.
Can 90W-7Ni-3Cu-SR be welded?
Not readily — weldability is rated not recommended (12/100). Fusion welding cracks and coarsens the tungsten skeleton — join by Ag-Cu brazing, electron-beam/inertia welding with qualified procedures, or by screws, pins and shrink fits.
What surface finishes work on 90W-7Ni-3Cu-SR?
Grind/lap for tight tolerances; electroless or electrolytic nickel plating (5–20 µm) is standard for corrosion protection and to prevent staining on handled shielding parts.
Can 90W-7Ni-3Cu-SR be formed, bent or molded?
Made only by press-and-sinter (liquid-phase sintering at ~1400–1500 °C); the W-Ni-Cu matrix tolerates very little cold work, so near-net pressing plus machining is the normal route.
What is the maximum service temperature of 90W-7Ni-3Cu-SR?
90W-7Ni-3Cu-SR 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.
Sources
- ASTM B777 Standard Specification for Tungsten Base, High-Density Metal — ASTM International (2022)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Tungsten Heavy Alloys) — ASM International (1990)
- Tungsten heavy alloy product datasheets (Plansee, Mi-Tech Metals, Midwest Tungsten Service, / ) — various producers (2024)
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.