Titanium Ti-6Al-5Zr-0.5Mo BSTA-AC
Heat-treated state
EN 3.7155
Used for thick discs and forgings where oil quenching is impractical; coarser transformed-beta gives slightly lower strength but the highest toughness and creep resistance.
Values for the BSTA-AC condition
Other Ti-6Al-5Zr-0.5Mo tempers and conditions
Ti-6Al-5Zr-0.5Mo is listed in 4 conditions; see the grade overview at Ti-6Al-5Zr-0.5Mo.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
BSTA-ACThis page BSTA | Used for thick discs and forgings where oil quenching is impractical; coarser transformed-beta gives slightly lower strength but the highest toughness and creep resistance. | 860 | 990 | 9 | 32 HRC | 1.1 % IACS |
Stress relieved | Applied to weldments and machined parts to remove residual stress without changing the transformed-beta structure; small drop in strength, slight ductility gain. | 870 | 990 | 11 | 32 HRC | 1.1 % IACS |
Annealed | Equiaxed/bimodal structure for bar and sheet: better ductility, low-cycle fatigue and formability, but noticeably lower creep resistance and toughness than the beta-treated condition. | 880 | 1,000 | 13 | 32 HRC | — |
BSTADefault Beta solution treated (≈1050 °C), oil quenched + aged 550 °C/24 h | Standard aerospace supply condition: basket-weave transformed-beta structure giving the best creep and fracture toughness at 450–520 °C. | 900 | 1,030 | 10 | 34 HRC | — |
What is Ti-6Al-5Zr-0.5Mo BSTA-AC?
Ti-6Al-5Zr-0.5Mo BSTA-AC is Ti-6Al-5Zr-0.5Mo heat treated to BSTA-AC — used for thick discs and forgings where oil quenching is impractical; coarser transformed-beta gives slightly lower strength but the highest toughness and creep resistance. Ti-6Al-5Zr-0.5Mo BSTA-AC has a yield strength of 860 MPa (125 ksi) and a tensile strength of 990 MPa (144 ksi) — stronger than 71% of titanium grades. Elongation at break is 9% and the elastic modulus is 120 GPa (17.4 Msi). Ti-6Al-5Zr-0.5Mo BSTA-AC has a density of 4.45 g/cm³ (0.161 lb/in³), lighter than 81% of titanium grades. It melts at 1,620°C (2,948 °F). BSTA is the default condition FabDigit quotes; BSTA-AC is available on request or by drawing note.
Advantages
- Stiff — 120 GPa (17.4 Msi), better than 98% of titanium grades
- High service temperature — 520°C (968 °F), better than 97% of titanium grades
- Tough — resists crack growth — 80 MPa·√m (72.8 ksi·√in), better than 81% of titanium grades
Limitations
- Limited ductility — 9%, worse than 97% of titanium grades
Ti-6Al-5Zr-0.5Mo BSTA-AC properties
Typical room-temperature values for Ti-6Al-5Zr-0.5Mo BSTA-AC; 22 are specific to this condition. Other listed values are Ti-6Al-5Zr-0.5Mo reference data and may not represent this condition. Bars are the position among titanium grades.
Physical3
Ti-6Al-5Zr-0.5Mo BSTA-AC has a density of 4.45 g/cm³ (0.161 lb/in³), lighter than 81% of titanium grades. It melts at 1,620°C (2,948 °F).
Mechanical16
Ti-6Al-5Zr-0.5Mo BSTA-AC has a yield strength of 860 MPa (125 ksi) and a tensile strength of 990 MPa (144 ksi) — stronger than 71% of titanium grades. Elongation at break is 9% and the elastic modulus is 120 GPa (17.4 Msi).
Thermal6
Ti-6Al-5Zr-0.5Mo BSTA-AC is rated for continuous service to 520°C (968 °F). It conducts heat at 7 W/m·K (4.04 BTU/hr·ft·°F), worse than 76% of titanium grades. Thermal expansion is 9 µm/m·K (5 µin/in·°F).
Electrical3
Ti-6Al-5Zr-0.5Mo BSTA-AC conducts electricity at 1.1 % IACS, worse than 67% of titanium grades.
Chemical & Environmental3
Corrosion resistance is excellent (88/100), worse than 77% of titanium grades.
Sustainability4
Producing a kilogram of Ti-6Al-5Zr-0.5Mo BSTA-AC takes about 660 MJ of energy and emits 44 kg of CO₂ — less than 57% of titanium grades. Typical recycled content is 25%.
Manufacturability8
Ti-6Al-5Zr-0.5Mo BSTA-AC's machinability is poor (18/100, worse than 83% of titanium grades); weldability very good (70/100); formability poor (27/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Ti-6Al-5Zr-0.5Mo BSTA-AC
Is Ti-6Al-5Zr-0.5Mo easy to machine?
Machine like a high-strength titanium alloy: rigid setup, sharp uncoated carbide or PVD-coated tools, low surface speed (20–35 m/min), heavy feed, flood high-pressure coolant, and never dwell — work hardening and fire risk from fine chips.
Can Ti-6Al-5Zr-0.5Mo be welded?
Readily GTAW/plasma/EB welded with full argon or vacuum shielding and matching filler; weld metal is fully transformed beta, so a 600 °C stress relief is normal and hydrogen/oxygen pickup must be avoided.
Can Ti-6Al-5Zr-0.5Mo be formed, bent or molded?
Hot work and form in the 900–1000 °C range with beta forging/final beta heat treatment for creep parts; cold forming is essentially limited to gentle bends with generous radii and springback allowance.
What surface finishes work on Ti-6Al-5Zr-0.5Mo?
Chemically mill or pickle in HNO₃/HF to remove alpha case after hot work, then anodise, shot peen or apply oxidation/anti-fretting coatings; polishes to a bright grey finish.
Ti-6Al-5Zr-0.5Mo 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 stabiliser, main solid-solution strengthener | 5.5 – 6.5 | 6 |
| Zrneutral element, boosts creep strength | 4.5 – 5.5 | 5 |
| Mobeta stabiliser for structure control | 0.4 – 0.6 | 0.5 |
| Sicreep-resistance addition in the IMI 685 version of this composition | 0.2 – 0.3 | 0.25 |
| Feimpurity | ≤ 0.15 | 0.05 |
| Oimpurity; controls strength and ductility | ≤ 0.15 | 0.1 |
| C | ≤ 0.05 | 0.02 |
| N | ≤ 0.04 | 0.01 |
| Hkept low to avoid hydride embrittlement | ≤ 0.01 | 0 |
| Ti | balance | — |
Ti-6Al-5Zr-0.5Mo BSTA-AC — frequently asked
What is Ti-6Al-5Zr-0.5Mo BSTA-AC used for?
Ti-6Al-5Zr-0.5Mo BSTA-AC is typically used for aero-engine casings, high-temperature airframe structure, compressor discs and rings, welded engine ducting and manifolds, beta-forged rotating hardware and hot-section brackets and mounts. In short: creep resistance to 520 °C; weldable near-alpha alloy; beta-processed for creep life.
What is the yield strength of Ti-6Al-5Zr-0.5Mo BSTA-AC?
Ti-6Al-5Zr-0.5Mo BSTA-AC has a typical yield strength of 860 MPa (125 ksi) and a tensile strength of 990 MPa (144 ksi) — stronger than 71% of titanium grades. Strength varies by condition: see the 4 listed tempers.
Is Ti-6Al-5Zr-0.5Mo BSTA-AC easy to machine?
Not especially — machinability is rated poor (18/100, worse than 83% of titanium grades). Machine like a high-strength titanium alloy: rigid setup, sharp uncoated carbide or PVD-coated tools, low surface speed (20–35 m/min), heavy feed, flood high-pressure coolant, and never dwell — work hardening and fire risk from fine chips.
Can Ti-6Al-5Zr-0.5Mo BSTA-AC be welded?
Yes — weldability is rated very good (70/100). Readily GTAW/plasma/EB welded with full argon or vacuum shielding and matching filler; weld metal is fully transformed beta, so a 600 °C stress relief is normal and hydrogen/oxygen pickup must be avoided.
What surface finishes work on Ti-6Al-5Zr-0.5Mo BSTA-AC?
Chemically mill or pickle in HNO₃/HF to remove alpha case after hot work, then anodise, shot peen or apply oxidation/anti-fretting coatings; polishes to a bright grey finish.
Can Ti-6Al-5Zr-0.5Mo BSTA-AC be formed, bent or molded?
Hot work and form in the 900–1000 °C range with beta forging/final beta heat treatment for creep parts; cold forming is essentially limited to gentle bends with generous radii and springback allowance.
What is the maximum service temperature of Ti-6Al-5Zr-0.5Mo BSTA-AC?
Ti-6Al-5Zr-0.5Mo BSTA-AC is rated for continuous use to about 520°C (968 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Ti-6Al-5Zr-0.5Mo BSTA and Ti-6Al-5Zr-0.5Mo BSTA-AC?
BSTA is the default condition — standard aerospace supply condition: basket-weave transformed-beta structure giving the best creep and fracture toughness at 450–520 °C. BSTA-AC: used for thick discs and forgings where oil quenching is impractical; coarser transformed-beta gives slightly lower strength but the highest toughness and creep resistance. Yield strength is 900 MPa in BSTA versus 860 MPa in BSTA-AC.
Sources
- IMI 685 (Ti-6Al-5Zr-0.5Mo-0.25Si) high-temperature titanium alloy data — IMI Titanium / Timet (1990)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (titanium alloys) — ASM International (1990)
- Materials Properties Handbook: Titanium Alloys — ASM International (1994)
- DIN 17851 / Werkstoff-Nr. 3.7155 titanium alloy designations — 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.