Titanium TC21 · heat-treated state
Titanium TC21 NBF-THT
Properties of the NBF-THT condition, compared with the other TC21 tempers.
Aerospace optimum for large TC21 forgings: basketweave microstructure giving the best simultaneous strength, toughness and crack-growth resistance.
What is TC21 NBF-THT?
TC21 NBF-THT is TC21 heat treated to NBF-THT — aerospace optimum for large TC21 forgings: basketweave microstructure giving the best simultaneous strength, toughness and crack-growth resistance. TC21 NBF-THT has a yield strength of 1,050 MPa (152 ksi) and a tensile strength of 1,140 MPa (165 ksi) — stronger than 96% of titanium grades. Elongation at break is 10% and the elastic modulus is 114 GPa (16.5 Msi). TC21 NBF-THT has a density of 4.58 g/cm³ (0.165 lb/in³), heavier than 86% of titanium grades. It melts at 1,600°C (2,912 °F). STA is the default condition FabDigit quotes; NBF-THT is available on request or by drawing note.
Advantages
- High strength — 1,050 MPa (152 ksi), better than 96% of titanium grades
- Tough — resists crack growth — 88 MPa·√m (80.1 ksi·√in), better than 95% of titanium grades
- High service temperature — 400°C (752 °F), better than 78% of titanium grades
Limitations
- Limited ductility — 10%, worse than 93% of titanium grades
- Low electrical conductivity — 1 % IACS, worse than 89% of titanium grades
- Difficult to weld — 50/100, worse than 89% of titanium grades
- Limited formability — 18/100, worse than 89% of titanium grades
TC21 NBF-THT properties
Typical room-temperature values for TC21 NBF-THT — 10 properties are specific to this condition; the rest are grade-level values shared by every TC21 temper. Each bar shows where the value sits among the titanium grades in FabDigit's library — further right is higher.
Physical3
TC21 NBF-THT has a density of 4.58 g/cm³ (0.165 lb/in³), heavier than 86% of titanium grades. It melts at 1,600°C (2,912 °F).
Mechanical16
TC21 NBF-THT has a yield strength of 1,050 MPa (152 ksi) and a tensile strength of 1,140 MPa (165 ksi) — stronger than 96% of titanium grades. Elongation at break is 10% and the elastic modulus is 114 GPa (16.5 Msi).
Thermal6
TC21 NBF-THT is rated for continuous service to 400°C (752 °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
TC21 NBF-THT conducts electricity at 1 % IACS, worse than 89% of titanium grades.
Chemical & Environmental3
Corrosion resistance is excellent (92/100), better than 53% of titanium grades.
Sustainability4
Producing a kilogram of TC21 NBF-THT takes about 700 MJ of energy and emits 45 kg of CO₂ — more than 74% of titanium grades. Typical recycled content is 20%.
Manufacturability7
TC21 NBF-THT's machinability is poor (15/100, worse than 97% of titanium grades); weldability fair (50/100); formability poor (18/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other TC21 tempers and conditions
TC21 is also supplied in 4 other conditions. The full side-by-side table is on the TC21 overview.
- STADefaultStandard delivered condition for forgings, bar and plate needing the full ~1100 MPa strength with good toughness.1,060 MPa yield · 38 HRC
- NBF-THTAerospace optimum for large TC21 forgings: basketweave microstructure giving the best simultaneous strength, toughness and crack-growth resistance.1,050 MPa yield · 38 HRC
- BAChoose for maximum fracture toughness and slow fatigue-crack growth in damage-tolerant primary structure, accepting lower ductility.1,010 MPa yield · 37 HRC
- DABalanced strength/ductility condition for plate, sheet and general structural parts where thermal stability matters more than peak strength.1,000 MPa yield · 36 HRC
- AnnealedSoftest supply condition for bar and plate that will be re-forged, machined heavily or heat treated by the part maker.940 MPa yield · 33 HRC
Working with TC21 NBF-THT
Is TC21 easy to machine?
Machine like a high-strength α+β titanium: rigid setups, sharp uncoated-carbide or coated inserts, 20–40 m/min surface speed, heavy flood coolant and no dwelling — work hardening and heat concentration cause rapid tool wear.
Can TC21 be welded?
GTAW, plasma, EBW and LBW in high-purity argon or vacuum are feasible with matching filler; the fusion zone loses toughness, so post-weld solution/aging or β anneal plus full NDT is normally specified.
Can TC21 be formed, bent or molded?
Essentially a hot-working alloy: forge just below or across the β transus (~950–970 °C) with tight temperature/strain-rate control, hot form sheet above 700 °C; cold forming is limited to gentle bends with large radii.
What surface finishes work on TC21?
Grit blast or chemically mill the alpha case after hot work, then pickle, anodize (Ti Type II/III) or apply Cu-free primers; shot peening is standard on fatigue-critical surfaces.
TC21 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 | 5.5 – 6.5 | 6 |
| Sn | 1.6 – 2.5 | 2 |
| Zr | 1.6 – 2.5 | 2 |
| Moβ stabiliser | 2.5 – 3.5 | 3 |
| Crβ stabiliser | 0.9 – 2 | 1.5 |
| Nb | 1.5 – 2.5 | 2 |
| Siraises creep/thermal stability | 0.06 – 0.15 | 0.1 |
| Feimpurity | ≤ 0.15 | — |
| Oimpurity | ≤ 0.15 | — |
| Cimpurity | ≤ 0.08 | — |
| Nimpurity | ≤ 0.05 | — |
| Himpurity | ≤ 0.02 | — |
| Ti | balance | — |
TC21 NBF-THT — frequently asked
What is TC21 NBF-THT used for?
TC21 NBF-THT is typically used for aircraft primary structural forgings, landing gear and bulkheads. In short: damage-tolerant aerospace titanium; higher strength than Ti-6Al-4V; forging and heavy-plate grade.
What is the yield strength of TC21 NBF-THT?
TC21 NBF-THT has a typical yield strength of 1,050 MPa (152 ksi) and a tensile strength of 1,140 MPa (165 ksi) — stronger than 96% of titanium grades. Strength varies by condition: see the 5 listed tempers.
Is TC21 NBF-THT easy to machine?
Not especially — machinability is rated poor (15/100, worse than 97% of titanium grades). Machine like a high-strength α+β titanium: rigid setups, sharp uncoated-carbide or coated inserts, 20–40 m/min surface speed, heavy flood coolant and no dwelling — work hardening and heat concentration cause rapid tool wear.
Can TC21 NBF-THT be welded?
With care — weldability is rated fair (50/100). GTAW, plasma, EBW and LBW in high-purity argon or vacuum are feasible with matching filler; the fusion zone loses toughness, so post-weld solution/aging or β anneal plus full NDT is normally specified.
What surface finishes work on TC21 NBF-THT?
Grit blast or chemically mill the alpha case after hot work, then pickle, anodize (Ti Type II/III) or apply Cu-free primers; shot peening is standard on fatigue-critical surfaces.
Can TC21 NBF-THT be formed, bent or molded?
Essentially a hot-working alloy: forge just below or across the β transus (~950–970 °C) with tight temperature/strain-rate control, hot form sheet above 700 °C; cold forming is limited to gentle bends with large radii.
What is the maximum service temperature of TC21 NBF-THT?
TC21 NBF-THT 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 TC21-STA and TC21-DA?
STA is the default condition — standard delivered condition for forgings, bar and plate needing the full ~1100 MPa strength with good toughness. DA: balanced strength/ductility condition for plate, sheet and general structural parts where thermal stability matters more than peak strength. Yield strength is 1,060 MPa in STA versus 1,000 MPa in DA.
Sources
- GJB 2218A / GB/T 2965 titanium and titanium alloy bar specifications (2020)
- TC21 high-strength high-toughness titanium alloy data (2022)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- (China Aeronautical Materials Handbook), Vol. 4 Titanium Alloys (2002)
- (titanium mill product price levels) (2025)
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.