Titanium Ti-6Al-2Sn-4Zr-6Mo STOA
Heat-treated state
UNS R56260
STOA = solution treated and overaged
Overaged cycle trading ~5–10 % tensile strength for better thermal stability, toughness and creep life in long-duty engine hardware.
Values for the STOA condition
Other Ti-6Al-2Sn-4Zr-6Mo tempers and conditions
Ti-6Al-2Sn-4Zr-6Mo is listed in 5 conditions; see the grade overview at Ti-6Al-2Sn-4Zr-6Mo.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Intermediate softer condition used for machining or hot working before the final aging cycle. | 900 | 970 | 15 | 32 HRC | 0.9 % IACS |
mill/duplex annealed | Lower-strength, more ductile and dimensionally stable condition for stock that will be re-heat-treated or for less critical parts. | 950 | 1,030 | 13 | 34 HRC | — |
Beta-STA | Pick when fracture toughness, creep and crack-growth resistance matter more than tensile ductility (heavier disks and thick forgings). | 1,010 | 1,100 | 8 | 37 HRC | 1 % IACS |
STOAThis page Solution treated and overaged | Overaged cycle trading ~5–10 % tensile strength for better thermal stability, toughness and creep life in long-duty engine hardware. | 1,020 | 1,100 | 12 | 36 HRC | 1 % IACS |
STADefault Solution treated and aged | Standard supply condition for bar, billet and forgings: highest strength for compressor disks, blades and high-load fittings up to ~400 °C. | 1,100 | 1,170 | 10 | 38 HRC | — |
What is Ti-6Al-2Sn-4Zr-6Mo STOA?
Ti-6Al-2Sn-4Zr-6Mo STOA is Ti-6Al-2Sn-4Zr-6Mo heat treated to STOA — overaged cycle trading ~5–10 % tensile strength for better thermal stability, toughness and creep life in long-duty engine hardware. Ti-6Al-2Sn-4Zr-6Mo STOA has a yield strength of 1,020 MPa (148 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 94% of titanium grades. Elongation at break is 12% and the elastic modulus is 114 GPa (16.5 Msi). Ti-6Al-2Sn-4Zr-6Mo STOA has a density of 4.65 g/cm³ (0.168 lb/in³), heavier than 90% of titanium grades. It melts at 1,590°C (2,894 °F). STA is the default condition FabDigit quotes; STOA is available on request or by drawing note.
Advantages
- High strength — 1,020 MPa (148 ksi), better than 94% of titanium grades
- High service temperature — 425°C (797 °F), better than 85% of titanium grades
Limitations
- Low fracture toughness — 42 MPa·√m (38.2 ksi·√in), worse than 99% of titanium grades
- Difficult to weld — 32/100, worse than 97% of titanium grades
- Limited formability — 14/100, worse than 97% of titanium grades
- Low electrical conductivity — 1 % IACS, worse than 89% of titanium grades
- Poor heat conductor — 6.9 W/m·K (3.99 BTU/hr·ft·°F), worse than 83% of titanium grades
Ti-6Al-2Sn-4Zr-6Mo STOA properties
Typical room-temperature values for Ti-6Al-2Sn-4Zr-6Mo STOA; 22 are specific to this condition. Other listed values are Ti-6Al-2Sn-4Zr-6Mo reference data and may not represent this condition. Bars are the position among titanium grades.
Physical3
Ti-6Al-2Sn-4Zr-6Mo STOA has a density of 4.65 g/cm³ (0.168 lb/in³), heavier than 90% of titanium grades. It melts at 1,590°C (2,894 °F).
Mechanical16
Ti-6Al-2Sn-4Zr-6Mo STOA has a yield strength of 1,020 MPa (148 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 94% of titanium grades. Elongation at break is 12% and the elastic modulus is 114 GPa (16.5 Msi).
Thermal6
Ti-6Al-2Sn-4Zr-6Mo STOA is rated for continuous service to 425°C (797 °F). It conducts heat at 6.9 W/m·K (3.99 BTU/hr·ft·°F), worse than 83% of titanium grades. Thermal expansion is 8 µm/m·K (4.44 µin/in·°F).
Electrical3
Ti-6Al-2Sn-4Zr-6Mo STOA conducts electricity at 1 % IACS, worse than 89% of titanium grades.
Chemical & Environmental3
Corrosion resistance is excellent (88/100), worse than 77% of titanium grades.
Sustainability4
Producing a kilogram of Ti-6Al-2Sn-4Zr-6Mo STOA takes about 700 MJ of energy and emits 42 kg of CO₂ — more than 74% of titanium grades. Typical recycled content is 25%.
Manufacturability7
Ti-6Al-2Sn-4Zr-6Mo STOA's machinability is poor (15/100, worse than 97% of titanium grades); weldability poor (32/100); formability not recommended (14/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Ti-6Al-2Sn-4Zr-6Mo STOA
Is Ti-6Al-2Sn-4Zr-6Mo easy to machine?
Machine rigid with sharp uncoated-carbide or coated carbide tools, low speed (~15–25 m/min in STA), heavy positive rake, generous high-pressure flood coolant; never dwell — work hardening and fire risk from fine chips.
Can Ti-6Al-2Sn-4Zr-6Mo be welded?
GTAW/EBW/LBW possible under high-purity inert gas or vacuum, but the aged microstructure is destroyed locally — full post-weld solution + age is needed and welded joints are avoided in rotating parts.
Can Ti-6Al-2Sn-4Zr-6Mo be formed, bent or molded?
Essentially a hot-working alloy: forge/roll just below the ~940 °C beta transus with controlled strain rate; cold forming is limited to gentle bends with large radii in the solution-treated state.
What surface finishes work on Ti-6Al-2Sn-4Zr-6Mo?
Chemically mill or pickle in HNO3/HF to strip alpha case after hot work; shot peen for fatigue life; decorative/anti-fret anodize or ion nitriding are the usual surface treatments — avoid cadmium and silver plating (embrittlement).
Ti-6Al-2Sn-4Zr-6Mo 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 |
|---|---|---|
| Alalpha stabilizer | 5.5 – 6.5 | 6 |
| Sn | 1.75 – 2.25 | 2 |
| Zr | 3.5 – 4.5 | 4 |
| Mobeta stabilizer, gives high hardenability | 5.5 – 6.5 | 6 |
| Fe | ≤ 0.15 | 0.05 |
| O | ≤ 0.15 | 0.11 |
| C | ≤ 0.04 | 0.02 |
| N | ≤ 0.04 | 0.01 |
| H0.015 max for some product forms | ≤ 0.01 | 0.01 |
| Yrotor-grade limit | ≤ 0.01 | — |
| Other, eachresiduals total 0.40 max | ≤ 0.1 | — |
| Ti | balance | — |
Ti-6Al-2Sn-4Zr-6Mo STOA — frequently asked
What is Ti-6Al-2Sn-4Zr-6Mo STOA used for?
Ti-6Al-2Sn-4Zr-6Mo STOA is typically used for turbine compressor disks, compressor blades and high-strength airframe forgings. In short: strongest alpha-beta forging alloy; 400 °C service capability; hardest to machine of family.
What is the yield strength of Ti-6Al-2Sn-4Zr-6Mo STOA?
Ti-6Al-2Sn-4Zr-6Mo STOA has a typical yield strength of 1,020 MPa (148 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 94% of titanium grades. Strength varies by condition: see the 5 listed tempers.
Is Ti-6Al-2Sn-4Zr-6Mo STOA easy to machine?
Not especially — machinability is rated poor (15/100, worse than 97% of titanium grades). Machine rigid with sharp uncoated-carbide or coated carbide tools, low speed (~15–25 m/min in STA), heavy positive rake, generous high-pressure flood coolant; never dwell — work hardening and fire risk from fine chips.
Can Ti-6Al-2Sn-4Zr-6Mo STOA be welded?
Not readily — weldability is rated poor (32/100). GTAW/EBW/LBW possible under high-purity inert gas or vacuum, but the aged microstructure is destroyed locally — full post-weld solution + age is needed and welded joints are avoided in rotating parts.
What surface finishes work on Ti-6Al-2Sn-4Zr-6Mo STOA?
Chemically mill or pickle in HNO3/HF to strip alpha case after hot work; shot peen for fatigue life; decorative/anti-fret anodize or ion nitriding are the usual surface treatments — avoid cadmium and silver plating (embrittlement).
Can Ti-6Al-2Sn-4Zr-6Mo STOA be formed, bent or molded?
Essentially a hot-working alloy: forge/roll just below the ~940 °C beta transus with controlled strain rate; cold forming is limited to gentle bends with large radii in the solution-treated state.
What is the maximum service temperature of Ti-6Al-2Sn-4Zr-6Mo STOA?
Ti-6Al-2Sn-4Zr-6Mo STOA is rated for continuous use to about 425°C (797 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Ti-6Al-2Sn-4Zr-6Mo-STA and Ti-6Al-2Sn-4Zr-6Mo-ST?
STA is the default condition — standard supply condition for bar, billet and forgings: highest strength for compressor disks, blades and high-load fittings up to ~400 °C. ST: intermediate softer condition used for machining or hot working before the final aging cycle. Yield strength is 1,100 MPa in STA versus 900 MPa in ST.
Sources
- AMS 4981 — Titanium Alloy Bars, Forgings and Rings 6Al-2Sn-4Zr-6Mo, Solution and Precipitation Heat Treated — SAE International (2018)
- Materials Properties Handbook: Titanium Alloys — ASM International (1994)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- ASTM B348 / UNS R56260 designation data — ASTM International (2021)
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.