Ti-6Al-4V vs Ti-6Al-4V ELI
Ti-6Al-4V (Grade 5) and Ti-6Al-4V ELI (Grade 23) share the same nominal 6Al-4V composition. ELI stands for Extra Low Interstitial - reduced O, N, C, Fe, and H for higher fracture toughness and cryogenic ductility.
Ti-6Al-4V
UNS R56400
Composition (wt %)
| Element | Min | Max |
|---|---|---|
| Ti | 87.7 | 91.0 |
| Al | 5.5 | 6.75 |
| V | 3.5 | 4.5 |
| Fe | 0.0 | 0.4 |
| O | 0.0 | 0.2 |
Ti-6Al-4V ELI
UNS R56401
Composition (wt %)
| Element | Min | Max |
|---|---|---|
| Ti | 87.7 | 91.0 |
| Al | 5.5 | 6.5 |
| V | 3.5 | 4.5 |
| Fe | 0.0 | 0.25 |
| O | 0.0 | 0.13 |
Key differences
| Aspect | Ti-6Al-4V | Ti-6Al-4V ELI | Engineering impact |
|---|---|---|---|
| Oxygen maximum | 0.20% O max | 0.13% O max | Lower O raises fracture toughness and reduces notch sensitivity, critical for implants and cryogenic vessels. |
| Iron maximum | 0.30% Fe max | 0.25% Fe max | Tighter Fe control improves beta-phase stability and biocompatibility. |
| Strength | Higher UTS (~950 MPa) | Slightly lower UTS (~860 MPa) | ELI trades ~10% strength for ~30-40% higher fracture toughness. Use standard Grade 5 when strength drives the design. |
| Typical specification | AMS 4928, ASTM B348 Gr 5 | AMS 4930, ASTM F136, ASTM B348 Gr 23 | ASTM F136 is the governing spec for surgical implants - Grade 5 is not biomedical-qualified. |
When to choose Ti-6Al-4V
- Aerospace airframe structural components
- Gas turbine blades and discs (compressor sections)
- High-strength fasteners and landing gear parts
When to choose Ti-6Al-4V ELI
- Orthopaedic and dental implants (per ASTM F136)
- Cryogenic pressure vessels and piping
- Fracture-critical aerospace parts where toughness governs
Frequently asked questions
Can I use Ti-6Al-4V ELI in place of standard Grade 5?
Technically yes for most aerospace applications, but ELI costs more and has lower strength minima. Do not substitute without stress re-analysis.
Is Grade 5 Ti-6Al-4V biocompatible?
Titanium itself is biocompatible, but surgical implants must meet ASTM F136 which only Grade 23 (ELI) satisfies.
How do I tell Grade 5 and Grade 23 apart from a mill cert?
Check the oxygen line: <=0.13% O and <=0.25% Fe indicates ELI. Grade 5 typically runs 0.15-0.20% O.