Titanium Ti-4Al-4Mo-2Sn-STA (Solution treated and aged)
Heat-treated state · default condition
EN 3.7185 · also IMI 550
Standard supply condition for aero-engine discs, shafts and high-strength forgings up to ~425 °C; use for peak strength in sections under ~50–75 mm.
Values for the STA condition
Other Ti-4Al-4Mo-2Sn tempers and conditions
Ti-4Al-4Mo-2Sn is listed in 4 conditions; see the grade overview at Ti-4Al-4Mo-2Sn.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Pick for stock bar/forgings that will be machined and heat treated later, or where maximum ductility and stability matter more than peak strength. | 900 | 1,010 | 16 | 32 HRC | — |
β-processed / β-annealed + aged | Choose when damage tolerance, creep and crack-growth resistance outrank ductility — transformed-β structure trades tensile elongation for toughness. | 970 | 1,080 | 8 | 35 HRC | — |
Stress relieved | Applied to welded or heavily machined parts to remove residual stress with only a small strength change from the prior condition. | 990 | 1,100 | 14 | 35 HRC | 1.1 % IACS |
STADefaultThis page Solution treated and aged | Standard supply condition for aero-engine discs, shafts and high-strength forgings up to ~425 °C; use for peak strength in sections under ~50–75 mm. | 1,030 | 1,150 | 13 | 36 HRC | — |
What is Ti-4Al-4Mo-2Sn-STA?
Ti-4Al-4Mo-2Sn-STA is Ti-4Al-4Mo-2Sn heat treated to STA — standard supply condition for aero-engine discs, shafts and high-strength forgings up to ~425 °C; use for peak strength in sections under ~50–75 mm. Ti-4Al-4Mo-2Sn-STA has a yield strength of 1,030 MPa (149 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 95% of titanium grades. Elongation at break is 13% and the elastic modulus is 114 GPa (16.5 Msi). Ti-4Al-4Mo-2Sn-STA has a density of 4.6 g/cm³ (0.166 lb/in³), heavier than 87% of titanium grades. It melts at 1,620°C (2,948 °F).
Advantages
- High strength — 1,030 MPa (149 ksi), better than 95% of titanium grades
- High service temperature — 425°C (797 °F), better than 85% of titanium grades
Limitations
- Difficult to weld — 28/100, worse than 99% of titanium grades
- Limited formability — 10/100, worse than 99% of titanium grades
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 90% of titanium grades
Ti-4Al-4Mo-2Sn-STA properties
Typical room-temperature values for Ti-4Al-4Mo-2Sn-STA; 19 are specific to this condition. Other listed values are Ti-4Al-4Mo-2Sn reference data and may not represent this condition. Bars are the position among titanium grades.
Physical3
Ti-4Al-4Mo-2Sn-STA has a density of 4.6 g/cm³ (0.166 lb/in³), heavier than 87% of titanium grades. It melts at 1,620°C (2,948 °F).
Mechanical16
Ti-4Al-4Mo-2Sn-STA has a yield strength of 1,030 MPa (149 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 95% of titanium grades. Elongation at break is 13% and the elastic modulus is 114 GPa (16.5 Msi).
Thermal6
Ti-4Al-4Mo-2Sn-STA is rated for continuous service to 425°C (797 °F). It conducts heat at 7.1 W/m·K (4.1 BTU/hr·ft·°F), worse than 68% of titanium grades. Thermal expansion is 9.4 µm/m·K (5.22 µin/in·°F).
Electrical3
Ti-4Al-4Mo-2Sn-STA conducts electricity at 1.1 % IACS, worse than 67% of titanium grades.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), worse than 93% of titanium grades.
Sustainability4
Producing a kilogram of Ti-4Al-4Mo-2Sn-STA takes about 700 MJ of energy and emits 45 kg of CO₂ — more than 74% of titanium grades. Typical recycled content is 25%.
Manufacturability8
Ti-4Al-4Mo-2Sn-STA's machinability is poor (16/100, worse than 93% of titanium grades); weldability poor (28/100); formability not recommended (10/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Ti-4Al-4Mo-2Sn-STA
Is Ti-4Al-4Mo-2Sn easy to machine?
Machine like a hard α+β titanium: rigid setup, sharp uncoated-carbide or PVD-coated tools, ~25–45 m/min in the STA condition, high-pressure flood coolant, positive feed to avoid work-hardening and never dwell.
Can Ti-4Al-4Mo-2Sn be welded?
GTAW/EBW/plasma in full inert shielding is possible but the aged microstructure is destroyed — post-weld solution + age (or at minimum stress relief) is required and weld ductility remains low, so welding is avoided on rotating parts.
Can Ti-4Al-4Mo-2Sn be formed, bent or molded?
Essentially a hot-work alloy: forge/roll just below the ~975 °C β transus and hot form at 700–850 °C; cold forming is limited to very gentle bends on annealed thin stock.
What surface finishes work on Ti-4Al-4Mo-2Sn?
Grit blast plus chemical (HF/HNO3) pickle to remove alpha case, then Type II anodize, ion nitriding or dry-film lube for galling/fretting control; polishes well but never leave scale from hot working.
Ti-4Al-4Mo-2Sn 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 |
|---|---|---|
| Alα stabiliser | 3 – 5 | 4 |
| Moβ stabiliser, solid-solution strengthening | 3.5 – 4.5 | 4 |
| Sn | 1.5 – 2.5 | 2 |
| Sicreep resistance via silicide precipitation | 0.3 – 0.7 | 0.5 |
| Fe | ≤ 0.2 | — |
| O | ≤ 0.2 | 0.13 |
| C | ≤ 0.08 | — |
| N | ≤ 0.05 | — |
| H | ≤ 0.01 | — |
| Ti | balance | — |
Ti-4Al-4Mo-2Sn-STA — frequently asked
What is Ti-4Al-4Mo-2Sn-STA used for?
Ti-4Al-4Mo-2Sn-STA is typically used for jet engine compressor discs, high-temperature fasteners, compressor blades and blisks, engine shafts and spacers, forged aero-engine rotating hardware and highly loaded airframe fittings. In short: high-strength engine disc alloy; service to 425 °C; forged, not formed.
What is the yield strength of Ti-4Al-4Mo-2Sn-STA?
Ti-4Al-4Mo-2Sn-STA has a typical yield strength of 1,030 MPa (149 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 95% of titanium grades. Strength varies by condition: see the 4 listed tempers.
Is Ti-4Al-4Mo-2Sn-STA easy to machine?
Not especially — machinability is rated poor (16/100, worse than 93% of titanium grades). Machine like a hard α+β titanium: rigid setup, sharp uncoated-carbide or PVD-coated tools, ~25–45 m/min in the STA condition, high-pressure flood coolant, positive feed to avoid work-hardening and never dwell.
Can Ti-4Al-4Mo-2Sn-STA be welded?
Not readily — weldability is rated poor (28/100). GTAW/EBW/plasma in full inert shielding is possible but the aged microstructure is destroyed — post-weld solution + age (or at minimum stress relief) is required and weld ductility remains low, so welding is avoided on rotating parts.
What surface finishes work on Ti-4Al-4Mo-2Sn-STA?
Grit blast plus chemical (HF/HNO3) pickle to remove alpha case, then Type II anodize, ion nitriding or dry-film lube for galling/fretting control; polishes well but never leave scale from hot working.
Can Ti-4Al-4Mo-2Sn-STA be formed, bent or molded?
Essentially a hot-work alloy: forge/roll just below the ~975 °C β transus and hot form at 700–850 °C; cold forming is limited to very gentle bends on annealed thin stock.
What is the maximum service temperature of Ti-4Al-4Mo-2Sn-STA?
Ti-4Al-4Mo-2Sn-STA 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-4Al-4Mo-2Sn-STA and Ti-4Al-4Mo-2Sn-ANN?
STA is the default condition — standard supply condition for aero-engine discs, shafts and high-strength forgings up to ~425 °C; use for peak strength in sections under ~50–75 mm. ANN: pick for stock bar/forgings that will be machined and heat treated later, or where maximum ductility and stability matter more than peak strength. Yield strength is 1,030 MPa in STA versus 900 MPa in ANN.
Sources
- IMI 550 (Ti-4Al-4Mo-2Sn-0.5Si) alloy data sheet — IMI Titanium / Timet (2000)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- Materials Properties Handbook: Titanium Alloys — ASM International (1994)
- ASM Handbook Vol. 13B — Corrosion: Materials — ASM International (2005)
- DIN 17851 / Werkstoff-Nr. 3.7185 titanium alloy designation — DIN (1990)
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.