Ti-6Al-4V Grade 5 vs Grade 23 (ELI): Key Differences and Selection Guide
Jan 19, 2026
Two Alloys, One Base Chemistry
Ti-6Al-4V Grade 5 (UNS R56400) and Ti-6Al-4V ELI Grade 23 (UNS R56401) share the same nominal composition: about 6% aluminum and 4% vanadium. The difference lies in purity. Grade 23 is the extra-low-interstitial version, with lower maximums for oxygen, iron, carbon and nitrogen. A common misconception is that Grade 23 contains palladium; it does not. Palladium is used in corrosion-resistant grades such as Grade 7 and Grade 11. Grade 23 achieves its advantages purely through tighter control of interstitial impurities, not through additional alloying elements.
Chemical Composition Compared
| Element | Grade 5 (Ti-6Al-4V) | Grade 23 (Ti-6Al-4V ELI) |
|---|---|---|
| Aluminum | 5.5-6.75% | 5.5-6.5% |
| Vanadium | 3.5-4.5% | 3.5-4.5% |
| Iron | 0.40% max | 0.25% max |
| Oxygen | 0.20% max | 0.13% max |
| Carbon | 0.08% max | 0.08% max |
| Nitrogen | 0.05% max | 0.05% max |
| Hydrogen | 0.015% max | 0.0125% max |
| Palladium | None | None |
The oxygen limit is the most significant difference: 0.20% maximum in Grade 5 versus 0.13% maximum in Grade 23. Oxygen strengthens titanium but embrittles it, so the lower limit in Grade 23 buys ductility and toughness at a small cost in maximum attainable strength.
Mechanical Properties Compared
In the annealed condition the two grades show similar tensile and yield strength. Per ASTM B348, Grade 5 bar has minimums of 895 MPa tensile and 828 MPa yield, while Grade 23 bar has minimums of 895 MPa tensile and 825 MPa yield, both with at least 10% elongation. The differences appear in secondary properties: Grade 23 exhibits higher fracture toughness, better ductility and superior resistance to fatigue crack growth, especially in thick sections and at low temperature.
| Property | Grade 5 | Grade 23 |
|---|---|---|
| Minimum tensile strength (bar) | 895 MPa | 895 MPa |
| Minimum yield strength (bar) | 828 MPa | 825 MPa |
| Minimum elongation | 10% | 10% |
| Fracture toughness | Good | Higher, especially in thick sections |
| Fatigue crack growth resistance | Standard | Improved |
| Low-temperature toughness | Adequate | Excellent, down to cryogenic temperatures |
Biocompatibility and Medical Use
Both grades are biocompatible and both have a history of medical use. However, regulatory practice and clinical preference favor Grade 23 for permanent implants because its higher toughness reduces the risk of fatigue failure under the cyclic loading experienced by hip stems, bone plates and dental implants. ASTM F136, the standard for wrought surgical implant material, is written specifically around the ELI chemistry. Grade 5 remains common in surgical instruments, external fixators and devices that do not remain in the body long term.
Application Comparison
| Grade 5 (Ti-6Al-4V) | Grade 23 (Ti-6Al-4V ELI) |
|---|---|
| Aerospace airframe and engine parts | Medical implants: orthopedic, dental, spinal |
| Marine and offshore components | Critical aerospace fittings and fasteners |
| Chemical processing equipment | Cryogenic and low-temperature components |
| High-performance sports equipment | High-integrity fracture-critical hardware |
| Automotive and motorsport parts | Devices requiring maximum fatigue resistance |
How to Choose the Right Grade
Select Grade 5 when the design is strength- and cost-driven: aerospace structures, marine hardware, chemical equipment and general engineering where the standard interstitial limits are acceptable. Select Grade 23 when the application is fracture-critical or body-contact: permanent implants, dental devices, cryogenic fittings and components that must tolerate fatigue cracks without fast propagation. Grade 23 costs more because the chemistry is tighter and the melting and testing requirements are stricter, so the extra expense is only justified where toughness or biocompatibility is decisive.
Frequently Asked Questions
1. Is Grade 23 the same alloy as Grade 5?
Chemically similar but not identical. Both are Ti-6Al-4V, but Grade 23 limits oxygen to 0.13% maximum versus 0.20% in Grade 5, plus tighter iron and hydrogen limits. The result is higher toughness at nearly the same strength.
2. Does Grade 23 contain palladium?
No. Palladium is not present in Grade 23. The misconception may come from confusing Grade 23 with palladium-bearing grades such as Grade 7 (Ti-0.15Pd) or Grade 11.
3. Which grade is used for dental implants?
Grade 23 (Ti-6Al-4V ELI) is the standard choice for load-bearing dental implants because of its fatigue resistance and biocompatibility, supplied to ASTM F136 or ISO 5832-3.
4. Is Grade 5 stronger than Grade 23?
In the annealed condition their specified minimum tensile strengths are the same at 895 MPa. In practice Grade 5 may reach slightly higher ultimate strengths, while Grade 23 provides better ductility and fracture toughness.
5. Can Grade 23 be used in aerospace?
Yes. ELI material is specified in aerospace for fracture-critical and cryogenic applications, for example AMS 4930 covers Ti-6Al-4V ELI bar and forgings.
6. Which grade is more expensive?
Grade 23. The tighter chemistry limits require higher-quality sponge, controlled melting practice and additional testing, which increases the cost of the finished bar or plate.
