GR5 (Ti-6Al-4V) is the titanium alloy behind most airframe hardware and the alloy most metal implants are machined from. The same chemistry serves both markets, but the purchase envelope differs: aerospace buys it to AMS or ASTM B348 with process and ultrasonic controls, while implant makers move to Grade 23 — Ti-6Al-4V ELI — under ASTM F136, where oxygen and iron are held tighter for toughness and fatigue life.
Why Aerospace Standardises on Grade 5 Titanium
Ti-6Al-4V delivers roughly the strength of a medium-alloy steel at about 56% of its density (4.43 g/cm³ against ~7.85 g/cm³), with predictable fatigue behaviour and enough corrosion resistance to skip plating entirely. It is the default airframe alloy for those reasons, and is commonly quoted for continuous service up to about 315 °C — beyond that, creep and oxidation push designers elsewhere.
- Specific strength — thin sections, lighter structure.
- Fatigue — predictable S-N behaviour when alpha case removal is controlled.
- Corrosion — no galvanic penalty against composites, no plating.
- Heat — usable well beyond aluminium limits; compressor stages run hotter than airframe structure.
Where Grade 5 Sits in an Aircraft
| Application area | Typical parts | Usual mill form | Specification route |
|---|---|---|---|
| Airframe | Fittings, brackets, seat tracks, wing attachments | Bar, plate, sheet, forgings | AMS airframe specifications; ASTM B348 for non-flight hardware |
| Landing gear | Axle beams, braces, actuator parts | Large bar, forgings | AMS bar and forging specifications with ultrasonic testing |
| Engine | Fan and compressor blades, discs, casings | Bar, forgings, plate | Engine-maker specifications, tighter cleanliness and UT |
| Systems | Hydraulic and pneumatic fittings | Bar, tube | AMS product specifications plus pressure-system rules |
| Fasteners | Bolts, hi-loks, nuts, collars | Bar, wire | Fastener product specifications, often in the STA condition |
Airframe buyers are driven by damage tolerance — microstructure, alpha case removal and surface finish. Engine buyers are driven by defect tolerance and heat, so cleanliness, ultrasonic quality level and grain control dominate the order.
Medical Implants: Why Grade 23 (Ti-6Al-4V ELI) Supersedes Plain Grade 5
Implant designs generally call for Grade 23, the extra-low-interstitial Ti-6Al-4V (UNS R56407). Lower oxygen and iron raise fracture toughness and improve fatigue crack growth behaviour — decisive in a stem or bone screw loaded cyclically for twenty years. Stock is bought to ASTM F136 for ELI, or ASTM F1472 where standard Ti-6Al-4V is acceptable, and machined into hip and knee stems, trauma plates, spinal cages and dental fixtures.
| Property (typical / per standard) | Grade 5 (Ti-6Al-4V) | Grade 23 (Ti-6Al-4V ELI) |
|---|---|---|
| UNS number | R56400 | R56407 |
| Oxygen, max | 0.20% | 0.13% |
| Iron, max | 0.30% | 0.25% |
| Tensile strength, annealed | 895 MPa min | 860 MPa min |
| Yield strength, annealed | 828 MPa min | 795 MPa min |
| Élongation | 10% min | 10% min |
| Typical use | Aerospace, industrial, marine hardware | Implants, cryogenic and high-toughness parts |
Note the trade: ELI is slightly weaker in tension but tougher. Its modulus of roughly 110 GPa still far exceeds cortical bone, so stress shielding drives porous and lattice designs — one reason much implant stock is now ELI powder for additive manufacturing rather than bar.
What to Put on the Purchase Order
- Grade and UNS — GR5 / UNS R56400, or Grade 23 / UNS R56407 for implant work.
- Specification — the document your drawing invokes: AMS 4911 for sheet and plate, AMS 4928 for bar, wire and forgings, ASTM B348 for general bar and billet, ASTM F136 or F1472 for implant stock.
- Condition — mill annealed, duplex or beta annealed, STA; plus grain size where fatigue-critical.
- Surface — turned, peeled, ground or pickled, and whether alpha case removal must be verified.
- Inspection — ultrasonic quality level, hardness, dimensional class, PMI on arrival.
- Documents — EN 10204 3.1 mill test report tied to the heat number.
Traceability Is the Real Differentiator
For aerospace and implant work the alloy is rarely the failure point — the lot history is. A heat number that cannot be walked back to melt, conversion and heat treatment is a non-conformance however good the test values look. Practical incoming checks are the 3.1 report matched to physical marking, hardness and dimensions, PMI to catch grade mix-ups in a warehouse shared with GR9 (Ti-3Al-2.5V) and GR2 (commercially pure titanium), and ultrasonic testing at the level the drawing calls for. Buyers comparing ASTM B348 against AMS 4928 for bar and billet will recognise the pattern; our GR5 (Ti-6Al-4V) alloy overview covers the metallurgy behind it.
Sourcing Grade 5 for Aerospace and Medical Work
As an integrated titanium supplier we handle GR5 and Grade 23 in bar, plate, sheet, wire and forgings, and pass your specification through to qualified production rather than paraphrasing it — the grade, condition and specification on your order are the ones printed on the mill test report. Inspection and certification scope, including ultrasonic level, PMI, alpha case verification and EN 10204 3.1 documentation, is confirmed against your drawing and RFQ before material is released. MOQs run from prototypes to production releases, lead time is quoted with the offer, and one accountable contact owns the order end to end. The titanium bar and rod range lists the forms we work to.
Frequently Asked Questions
Is Grade 5 titanium the same as Ti-6Al-4V?
Yes. Grade 5, Ti-6Al-4V and UNS R56400 describe one alloy — an ASTM grade number, a chemistry name and a UNS code for the same material. Grade 23 is the extra-low-interstitial variant, UNS R56407.
Can Grade 5 be used for medical implants?
It can, and ASTM F1472 covers wrought Ti-6Al-4V for surgical implants. Most new designs nevertheless specify Grade 23 to ASTM F136, because tighter oxygen and iron limits improve fracture toughness and fatigue crack growth resistance.
What is the maximum service temperature for Ti-6Al-4V?
Airframe structure is commonly quoted to about 315 °C for continuous service, with engine compressor applications running hotter for shorter lives. Above those ranges creep and oxidation become limiting, so confirm the allowable with your design authority.
Does Grade 5 need ultrasonic testing for aerospace?
Not automatically. Airframe fittings and landing gear parts frequently require it while non-flight hardware often does not, so state the quality level on the purchase order — ultrasonic inspection is not included unless it is invoked.
Get a Quote for Aerospace and Medical Grade Titanium
Send grade, specification, condition, form, sizes and inspection requirements to FDtitanium and we will return a graded offer with mill test report scope, ultrasonic and PMI arrangements, and lead time stated up front.
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