Titanium
Titanium TC21
Properties, tempers, machining, finishes and uses — values shown for the STA condition.
TC21 is a high-strength, high-toughness α–β titanium alloy developed for damage-tolerant primary aircraft structure, supplied mainly as forgings and heavy plate in Annealed, DA, STA, BA and NBF-THT conditions.
Reference datasheet — TC21 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
What is TC21?
TC21 is a high-strength, high-toughness α–β titanium alloy developed for damage-tolerant primary aircraft structure, supplied mainly as forgings and heavy plate in Annealed, DA, STA, BA and NBF-THT conditions. In the default condition it provides 1060 MPa yield, 1150 MPa tensile, 10% elongation and 350 HB (38 HRC), so engineers select it where fracture toughness and crack-growth resistance must accompany high static strength. Limits are a maximum service temperature of about 350 °C, very low machinability (score 16), heavy reliance on hot working, and restricted mill availability. Ti-6Al-4V is the usual lower-cost substitute where damage tolerance is less critical. TC21 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). TC21 has a yield strength of 1,060 MPa (154 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 97% of titanium grades. Elongation at break is 10% and the elastic modulus is 114 GPa (16.5 Msi).
What is TC21 used for?
- aircraft primary structural forgings
- landing gear
- bulkheads
Advantages
- High strength — 1,060 MPa (154 ksi), better than 97% 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 properties
Typical room-temperature values for TC21-STA (standard delivered condition for forgings, bar and plate needing the full ~1100 mpa strength with good toughness), compiled from standards, handbooks and producer data. Each bar shows where the value sits among the titanium grades in FabDigit's library — further right is higher. Other conditions have their own pages: see tempers.
Physical3
TC21 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 has a yield strength of 1,060 MPa (154 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 97% of titanium grades. Elongation at break is 10% and the elastic modulus is 114 GPa (16.5 Msi).
Thermal6
TC21 is rated for continuous service to 350°C (662 °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 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 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's machinability is poor (16/100, worse than 93% of titanium grades); weldability fair (50/100); formability poor (18/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
TC21 tempers and conditions
TC21 is supplied in 5 conditions, each with its own property set. Open one for its full datasheet. STA is what FabDigit quotes unless the drawing says otherwise.
- 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
| Condition | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
STADefault solution treated and aged | Standard delivered condition for forgings, bar and plate needing the full ~1100 MPa strength with good toughness. | 1,060 | 1,150 | 10 | 38 HRC | — |
mill/single anneal (hot-worked + stress relief) | Softest supply condition for bar and plate that will be re-forged, machined heavily or heat treated by the part maker. | 940 | 1,030 | 13 | 33 HRC | — |
duplex (double) annealed | Balanced strength/ductility condition for plate, sheet and general structural parts where thermal stability matters more than peak strength. | 1,000 | 1,090 | 12 | 36 HRC | — |
beta annealed / beta heat treated (lamellar structure) | Choose for maximum fracture toughness and slow fatigue-crack growth in damage-tolerant primary structure, accepting lower ductility. | 1,010 | 1,100 | 8 | 37 HRC | — |
near-beta forged plus triple heat treatment (basketweave) | Aerospace optimum for large TC21 forgings: basketweave microstructure giving the best simultaneous strength, toughness and crack-growth resistance. | 1,050 | 1,140 | 10 | 38 HRC | — |
Working with TC21
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.
Strength versus weight in the titanium family
Yield strength against density for every titanium grade FabDigit runs. TC21 is highlighted; hover a dot for its name, or open the interactive family chart.
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 | — |
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.
Surface treatments FabDigit runs on titanium parts — pick them in the quote configurator or call them out on the drawing.
Thermal Spray
- Plasma Spray
Equivalent designations
Standards and trade names that resolve to Titanium TC21 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
How much does TC21 cost?
TC21 is a high-cost titanium ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
TC21 — frequently asked
What is TC21 used for?
TC21 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?
TC21 has a typical yield strength of 1,060 MPa (154 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 97% of titanium grades. Strength varies by condition: see the 5 listed tempers.
Is TC21 easy to machine?
Not especially — machinability is rated poor (16/100, worse than 93% 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 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?
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 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?
TC21 is rated for continuous use to about 350°C (662 °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.
How much does TC21 cost?
TC21 is a high-cost titanium ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.