Alpha-Beta Titanium Alloys
Alpha-beta titanium alloys carry enough beta stabilizer — 4 % vanadium in Ti-6Al-4V, molybdenum or iron in the others — to hold a mixture of both phases at room temperature, which is what makes them heat-treatable: annealed Grade 5 yields about 880 MPa, and solution treating and aging lifts that to roughly 1,100 MPa in sections under 25 mm. Grade 5 alone is about half of all titanium produced, so it is the grade every drawing, stock list and machining data sheet is built around; Grade 23 is the same alloy with oxygen held to 0.13 % for fracture toughness in implants, and Grade 9 is the leaner Ti-3Al-2.5V for cold-worked tube.
Popular alpha-beta titanium grades
Compare in the explorer| Grade | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|
| Grade 5 | 880 | 950 | 4.43 | Poor | Very good | The default titanium; bar, plate, sheet, forgings |
| Grade 23 | 850 | 930 | 4.43 | Poor | Very good | ELI implant grade; fracture-critical and cryogenic parts |
| Grade 9 | 570 | 690 | 4.48 | Poor | Very good | Tubing and cold-formed sheet; frames, hydraulic lines |
| Ti-6Al-7Nb | 900 | 1,000 | 4.52 | Poor | Good | Vanadium-free orthopaedic implant alloy |
| Ti-6Al-6V-2Sn | 980 | 1,050 | 4.54 | Poor | Fair | Deep-hardening airframe forgings to 1,100 MPa |
| Ti-17 | 1,075 | 1,150 | 4.65 | Poor | Poor | Fan and compressor discs; thick heat-treated sections |
| Ti Grade 29 | 830 | 900 | 4.43 | Poor | Very good | Grade 23 with ruthenium for sour oil and gas |
All 26 alpha-beta titanium grades
Choose alpha-beta titanium for
Airframe fittings, brackets and fasteners, engine parts below about 400 °C, orthopaedic and dental implants, surgical instruments, hydraulic and bicycle tubing, racing suspension and connecting rods, marine shafts and subsea hardware, and any machined part where the customer has written "titanium" without a temperature or acid duty attached — Grade 5 is the default the rest of the family is compared against.
Look elsewhere when
The service is corrosion alone and load is small (Grade 2 costs less and forms and welds more easily), the metal runs above about 400 °C (Ti-6242 or IMI 834), the forging is thick and must exceed 1,100 MPa yield (Ti-10-2-3, Ti-5553), the part is a spring or cold-formed sheet (Ti-15-3, Ti Grade 19), or the design is stiffness-limited — at 114 GPa titanium flexes 45 % more than steel for the same section and 17-4 PH or 4340 may simply be the better answer.
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Alpha-beta titanium by application
- Machined aerospace and industrial parts
- Grade 5 annealed for fittings, brackets, housings and shafts; specify STA only when the extra 15–20 % strength is worth the section limit and the toughness loss. Ti-6Al-6V-2Sn or Ti-17 when a thick forging must hold 1,000 MPa yield through the core.
- Implants and medical devices
- Grade 23 (ASTM F136) for hip and knee stems, plates, screws and spinal hardware; Ti-6Al-7Nb (ASTM F1295) where the surgeon or the market wants a vanadium-free alloy; Grade 5 for instruments and external fixators.
- Tubing, frames and formed sheet
- Grade 9 for hydraulic lines, bicycle and wheelchair frames, exhausts and roll cages — it cold-bends at about 3 t, welds like Grade 5 and reaches 725 MPa yield in the cold-worked, stress-relieved tube condition.
- Fasteners and high-load pins
- Grade 5 STA for bolts, pins and lugs (AMS 4967, about 1,100 MPa yield) with rolled threads; Ti-6Al-6V-2Sn where a larger fastener must be through-hardened; roll or coat the threads, because titanium on titanium galls.
Working with alpha-beta titanium
- Machining
- The benchmark for hard-to-cut metals: 30–40 % of the surface speed of alloy steel, sharp uncoated or AlTiN carbide, high feed, positive rake, flood coolant and a rigid setup, because the low modulus lets the part deflect and chatter. Annealed Grade 5 and Grade 23 machine alike; STA stock at about 36–40 HRC cuts 20 % slower. Rough, stress-relieve at 480–650 °C, then finish for ±0.02 mm.
- Welding
- TIG, plasma, laser and electron-beam with ERTi-5 (ERTi-23 for ELI parts) under full argon shielding of face, root and trailing zone. Annealed Grade 5 welds retain about 90 % of base strength; STA parts lose the aging response in the heat-affected zone and must be re-aged. Ti-6Al-6V-2Sn and Ti-17 are not recommended for fusion welding.
- Heat treatment
- Mill anneal at 700–790 °C for the standard condition; solution treat at 900–955 °C, water quench and age 4–8 h at 480–595 °C for STA — worth 15–20 % more yield in sections up to about 25 mm, less beyond because the centre cannot quench fast enough. Stress-relieve every machined part at 480–650 °C to hold tolerance. Vacuum or argon above 500 °C; any alpha case from air exposure must be machined or pickled off.
- Finishing
- Bead blast, brushed or polished as machined; anodize Type II or III per AMS 2488 for anti-galling and fatigue, or colour-anodize for identification — the colours are interference films, not dye. Passivate implants per ASTM F86. PVD TiN or DLC on sliding surfaces, since bare Grade 5 wears and galls badly against itself and against steel.
Other titanium series
Alpha-Beta Titanium Alloys — frequently asked
What is alpha-beta titanium?
Alpha-beta titanium alloys carry enough beta stabilizer — 4 % vanadium in Ti-6Al-4V, molybdenum or iron in the others — to hold a mixture of both phases at room temperature, which is what makes them heat-treatable: annealed Grade 5 yields about 880 MPa, and solution treating and aging lifts that to roughly 1,100 MPa in sections under 25 mm. Grade 5 alone is about half of all titanium produced, so it is the grade every drawing, stock list and machining data sheet is built around; Grade 23 is the same alloy with oxygen held to 0.13 % for fracture toughness in implants, and Grade 9 is the leaner Ti-3Al-2.5V for cold-worked tube.
Which grade of alpha-beta titanium should I use?
Grade 5 annealed unless the drawing says otherwise: about 880 MPa yield, 4.43 g/cm³, available in every mill form, and the reference alloy for machining, welding and anodizing data. Grade 23 (Ti-6Al-4V ELI, ASTM F136) for anything that goes inside the body or must stay tough at cryogenic temperature — same machining, about 5 % lower strength, twice the fracture toughness. Grade 9 (Ti-3Al-2.5V) when the part is tube or cold-formed sheet: 480 MPa yield annealed, 725 MPa cold-worked and stress-relieved, and it bends where Grade 5 would crack. Ti-6Al-7Nb (ASTM F1295) is the vanadium-free implant alloy specified by some orthopaedic houses in place of Grade 23. Ti-6Al-6V-2Sn and Ti-17 are the deep-hardening airframe and fan-disc alloys that reach 1,000–1,100 MPa yield in thick forgings at the cost of weldability. Ti Grade 29 is Grade 23 plus 0.1 % ruthenium for sour-gas risers and downhole hardware.
Which grade of alpha-beta titanium is the strongest?
Ti-17 has the highest yield strength in the series at 1,075 MPa; TC21 follows at 1,060 MPa. Values are for each grade's default condition.
Which grade of alpha-beta titanium is easiest to machine?
Grade 9 (machinability poor, 28/100), then B817 Type II (20/100).
Is alpha-beta titanium heat-treatable?
Yes. These grades gain their strength from heat treatment; the conditions and their properties are listed on each grade page.
Grade 5 or Grade 23?
Same Ti-6Al-4V alloy; Grade 23 caps oxygen at 0.13 % (versus 0.20 %), iron at 0.25 % and nitrogen and hydrogen lower still. That costs about 5 % yield strength (795 MPa minimum against 828) and buys roughly twice the fracture toughness, better fatigue-crack resistance and ductility down to 20 K. Specify Grade 23 for implants (ASTM F136), fracture-critical aerospace parts and cryogenic hardware; use Grade 5 for everything else — it is cheaper, more widely stocked and machines and welds the same way.
Annealed or STA for a Grade 5 part?
Annealed for most parts: about 880 MPa yield, the best toughness and weldability, and no section limit. Solution-treated-and-aged lifts yield to roughly 1,100 MPa but only in sections thinner than about 25 mm, drops fracture toughness by a third, distorts during the water quench and cannot be welded without re-aging. It is worth specifying for fasteners, pins and thin high-stress lugs; for a machined housing or bracket the extra strength rarely pays for the extra process and the tighter machining allowance.