The real difference between grade 5 and grade 23 titanium is a fraction of a percent of oxygen. Grade 5 (Ti-6Al-4V) allows up to 0.20% oxygen; grade 23 (Ti-6Al-4V ELI, or Extra Low Interstitial) caps it at 0.13%. That tighter limit trades about 4% of static strength for dramatically better fracture toughness, fatigue life, and cryogenic ductility, which is why ASTM F136 makes grade 23 the standard for permanent surgical implants.
A quality engineer at a spinal implant manufacturer found out how much that difference matters. Her team ordered “Ti-6Al-4V round bar” for a new rod design, and the mill delivered ASTM B348 material. It was stronger than the grade 23 she had specified and cheaper too. At incoming inspection, she flagged the heat anyway because the engineering print called for ASTM F136 grade 23 ELI, and the lot failed the paperwork within an hour. The alloy name matched. The specification did not.
This guide compares grade 5 vs grade 23 titanium in full: what ELI means, how the two chemistries differ, how their mechanical properties compare, which standards apply to which buying decision, where grade 23 is mandatory, and whether its cost premium is worth it. You’ll finish knowing exactly which variant to put on your next print.
Key Takeaways
- Grade 5 (Ti-6Al-4V, UNS R56400) and grade 23 (Ti-6Al-4V ELI, UNS R56401) are the same alpha-beta alloy. Grade 23 is simply the “Extra Low Interstitial” version with oxygen capped at 0.13% (vs 0.20%) and iron at 0.25% (vs 0.40%).
- Grade 5 is the stronger grade at roughly 895 MPa minimum tensile / 828 MPa minimum yield (annealed). Grade 23 runs about 860 MPa / 795 MPa, trading ~4% strength for roughly 35-60% higher fracture toughness and about 20% higher fatigue endurance.
- ASTM F136 (and its international counterpart ISO 5832-3) is the surgical-implant specification for grade 23 ELI. Permanent load-bearing implants require it; standard grade 5 is generally not accepted for that role.
- Grade 23 ELI is also specified for cryogenic service down to -253°C (liquid hydrogen) and fracture-critical aerospace parts, bought to AMS 4930/4931.
- Grade 23 costs about 15-40% more per kg than grade 5 (typically 20-30%). The premium pays only when fatigue, toughness, cryogenic service, or implant certification actually governs the design.
What Is Grade 5 Titanium (Ti-6Al-4V)?
Grade 5 titanium is an alpha-beta alloy containing roughly 6% aluminum and 4% vanadium, with the balance titanium. It is identified as Ti-6Al-4V, UNS R56400, and 3.7165, and it is the workhorse of the titanium industry, accounting for about half of all titanium metal consumed globally.
Aluminum stabilizes the alpha phase and vanadium stabilizes the beta phase. That dual-phase structure is what gives grade 5 its unusual balance: it is far stronger than any commercially pure titanium grade, yet it keeps enough ductility to be forged, machined, and welded. Designers reach for it when the priority is the highest strength-to-weight ratio at the lowest cost.
Where you see grade 5 every day: airframe structures, engine parts, and fasteners in aerospace; marine hardware; high-performance automotive components; and industrial equipment where maximum static strength drives the design. For a complete look at the alloy, our Grade 5 titanium guide covers its properties, applications, and buying considerations.
What Is Grade 23 Titanium (Ti-6Al-4V ELI)?
Grade 23 titanium is the same Ti-6Al-4V alloy with one crucial refinement: it is the Extra Low Interstitial (ELI) version, identified as Ti-6Al-4V ELI, UNS R56401, and 3.7165. The nominal alloy chemistry is identical. What changes are the maximum limits on the interstitial impurities oxygen, iron, nitrogen, carbon, and hydrogen, and oxygen is the one that matters most.
Grade 23 is not a separate alloy family. It is a higher-purity refinement of grade 5 produced to a tighter chemistry window. That is why the two grades look alike, machine alike, and share the same density and modulus. The difference shows up in how they behave when a crack tries to grow, not in the name on the datasheet.
Our titanium grade chart shows where grade 23 sits in the wider grade family, and the titanium grade 2 vs grade 5 comparison explains how the alloy grades relate to the commercially pure grades.
What Does “ELI” Mean in Titanium?
ELI stands for Extra Low Interstitial. In titanium metallurgy, an interstitial is a small atom, mostly oxygen, nitrogen, carbon, and hydrogen, that fits between the larger titanium atoms in the crystal lattice.
These small atoms are powerful strengtheners. They block dislocation movement, which makes the metal harder and stronger. But they also pin those dislocations, which makes the metal more brittle and less tolerant of a growing crack. Oxygen in particular is a strong alpha stabilizer, so even a small increase raises strength while cutting ductility, fracture toughness, and fatigue crack growth resistance.
The ELI designation exists precisely to control this trade. By holding oxygen below 0.13% instead of 0.20%, grade 23 accepts a modest strength loss to recover the toughness and fatigue resistance that a safety-critical or implanted part needs. Every other property difference between grade 5 and grade 23 flows from this one decision about interstitial limits.
Grade 5 vs Grade 23 Titanium: Chemical Composition Compared
The composition table below shows the defining differences. The alloying elements aluminum and vanadium stay the same; the interstitial limits, especially oxygen and iron, are what separate the two grades.
| Element | Grade 5 (Ti-6Al-4V, R56400) | Grade 23 (Ti-6Al-4V ELI, R56401) |
|---|---|---|
| Titanium | Balance | Balance |
| Aluminum | 5.50-6.75% | 5.50-6.50% |
| Vanadium | 3.50-4.50% | 3.50-4.50% |
| 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 | 0.012% max |
The oxygen limit is the headline. Cutting it from 0.20% to 0.13% is the entire reason grade 23 exists. The iron limit also drops from 0.40% to 0.25%, and hydrogen tightens slightly, both of which help weldability and resistance to hydrogen embrittlement.
Watch for the naming trap in procurement. Chinese mills call grade 5 TC4 and grade 23 TC4 ELI, and some catalogs label both simply “Ti-6Al-4V.” The alloy name alone never proves which grade you’re buying. Only the governing standard and the Mill Test Report, which must show oxygen at or below 0.13%, confirm grade 23. A heat that passes commercial ASTM B348 can still fail ASTM F136 or AMS 4930 on iron or oxygen alone.
Grade 5 vs Grade 23 Titanium: Mechanical Properties Compared
The mechanical table below summarizes typical annealed values. Strength floors vary a little by standard revision and product form, so treat the numbers as working comparisons rather than guarantees.
| Property (annealed) | Grade 5 (Ti-6Al-4V) | Grade 23 (Ti-6Al-4V ELI) |
|---|---|---|
| Minimum tensile strength | ~895 MPa | ~860 MPa |
| Minimum yield strength | ~828 MPa | ~795 MPa |
| Elongation | ~10-14% | ~10-15% |
| Fracture toughness (K_IC) | ~55-70 MPa√m | ~75-90 MPa√m |
| Fatigue endurance limit (10^7 cycles) | ~517 MPa | ~621-655 MPa |
| Charpy V-notch impact (room temp) | ~20-40 J | ~40-60 J |
| Density | 4.43 g/cm³ | 4.43 g/cm³ |
| Elastic modulus | ~110-114 GPa | ~110-114 GPa |
Strength: Grade 5 Wins, Slightly
Grade 5 is the stronger grade. With more oxygen and iron acting as strengtheners, it carries a higher minimum tensile and yield strength in the annealed condition, and both grades can be heat treated to the solution-treated-and-aged (STA) condition for higher strength still.
If your design is static-strength-limited, meaning the part is operating near its yield point and rarely sees cyclic loading, the extra few percent of strength in grade 5 is real value you pay nothing extra for.
Toughness, Ductility, and Fatigue: Grade 23 Wins Clearly
Where grade 23 dominates is damage tolerance. With fewer interstitial atoms pinning the lattice, a crack in grade 23 grows more slowly and the material absorbs more energy before it fractures. Reported fracture toughness runs about 75-90 MPa√m versus 55-70 MPa√m for grade 5, a jump of roughly 35-60%. Fatigue endurance improves by about 20%, and room-temperature Charpy impact energy roughly doubles, from about 20-40 J to 40-60 J.
Those numbers translate directly into service life. A hip stem that survives about 15 years of walking cycles in grade 5 may reach about 20 years in grade 23, because fatigue crack growth, not static overload, is what ends most implants. The same logic applies to aircraft parts that must never fail in flight. For a closer look at how grade 5 behaves under cyclic loading compared with the CP grades, see our grade 5 vs grade 2 strength comparison.
Not sure whether your application is strength-limited or fatigue-limited? That single question decides most grade 5 vs grade 23 choices. Our technical consultation team works through service conditions and loading with engineers every week to separate the two cases.
ASTM F136, F1472, and AMS 4930: The Standards Map
The fastest way to understand grade 5 vs grade 23 is through the specifications that govern them. The same ELI chemistry is bought under different standards depending on the application, and knowing which standard your print cites settles most arguments.
| Standard | Material | Typical Use |
|---|---|---|
| ASTM F136 | Grade 23 ELI (R56401) | Wrought surgical-implant alloy; permanent load-bearing implants |
| ISO 5832-3 | Grade 23 ELI | International counterpart referenced for implant alloy alongside ASTM F136 |
| AMS 4930 / AMS 4931 | Grade 23 ELI | Aerospace bar/forgings/rings and sheet/plate |
| ASTM F1472 | Grade 5 (R56400) | Surgical-use Ti-6Al-4V where standard (non-ELI) chemistry is acceptable |
| AMS 4928 / AMS 4911 | Grade 5 | Aerospace bar and sheet |
| ASTM B348 / B265 | Both grades | General commercial bar/billet and sheet/plate |
Three details matter here.
First, ASTM F136 IS the grade 23 ELI specification. When a supplier quotes “Ti-6Al-4V per ASTM F136,” that material is ELI by definition, because the standard only covers the extra-low-interstitial grade. It is not an option within the standard; it is the standard.
Second, ASTM F1472 is the surgical specification for standard grade 5 chemistry. It exists because some medical hardware does not need the ELI grade, and we cover that split in the next section.
Third, ASTM F136 carries heavier process and testing requirements than commercial specs. It demands double or triple vacuum-arc-remelting (VAR), microcleanliness evaluation per ASTM F1440, and fatigue testing, plus full lot traceability in the Mill Test Report. AMS 4930 and 4931 apply the same ELI chemistry to aerospace bar, forgings, rings, sheet, and plate, so aerospace buyers and medical buyers are often purchasing the same material under different paperwork.
Why ASTM F136 Grade 23 Is Required for Medical Implants
Permanent, load-bearing surgical implants are where grade 23 earns its reputation. A hip or knee component, a spinal rod or cage, a trauma plate, or a dental implant must survive millions of loading cycles inside the human body without a fatigue failure, because a fractured implant means revision surgery.
Grade 23 ELI meets that demand on three fronts:
- Its lower oxygen content delivers the fracture toughness and fatigue resistance those cyclic loads demand.
- Its stable titanium oxide layer gives excellent corrosion resistance in body fluids and low metal-ion release.
- Its biocompatibility supports osseointegration, the process by which bone grows onto the implant surface.
For these reasons, ASTM F136 grade 23, aligned with ISO 5832-3 in international markets, is the standard of care for permanent implants. Regulators such as the US FDA (21 CFR 888) and the EU MDR generally treat standard grade 5 as unsuitable for that role.
That does not mean grade 5 has no place in medical devices. ASTM F1472 covers grade 5 Ti-6Al-4V for surgical use in non-load-bearing or temporary applications: surgical instruments, trial implants, spacers, washers, and external fixation hardware. In those roles, the higher strength and lower cost of grade 5 are advantages, and no implant is at stake.
For non-implant medical hardware and instruments, stainless steel is the practical alternative many buyers choose. 316 stainless steel resists the corrosion and repeated autoclave sterilization of surgical service, welds easily, and costs a small fraction of titanium. DAPU supplies 316 stainless steel products and stainless steel pipes that cover most instrument and equipment applications. Reserve titanium for the implanted components where nothing else will do.
Grade 23 in Cryogenic and Aerospace Service
The same low interstitial content that protects implants also protects components at extreme low temperatures, where grade 5 becomes the wrong choice.
As temperature drops, standard grade 5 Ti-6Al-4V loses ductility and can embrittle, in part because its higher oxygen content promotes alpha-2 precipitation in the microstructure. Grade 23 ELI avoids that problem. Its lower oxygen preserves toughness all the way down to about -253°C, the temperature of liquid hydrogen, and it retains over 90% of its room-temperature strength near -200°C. That is why cryogenic propellant tanks, pressure vessels, and piping for launch vehicles and satellite propulsion are specified in grade 23, not grade 5.
A launch-vehicle program we work alongside learned this trade-off directly. An early design quoted grade 5 for a liquid-oxygen tank liner because the material was cheaper and the strength numbers looked equal. Cryogenic testing showed the problem: the grade 5 liner lost ductility at operating temperature, and the fracture-toughness margin disappeared.
Engineering switched the liner to grade 23 ELI, and qualification testing passed with the toughness margin the design required. The lesson was not that grade 5 is a bad alloy. It was that grade 5 is the wrong alloy when the failure mode is brittle fracture at -253°C.
Beyond cryogenics, grade 23 appears in fracture-critical aerospace components, landing-gear parts, large structural forgings, and fasteners where damage tolerance, not peak strength, drives the design. Aerospace buyers procure it to AMS 4930 for bar and AMS 4931 for sheet and plate.
If you are weighing titanium against steel or nickel alloys in these systems, our titanium vs stainless steel comparison explains why titanium is often the lightest way to get the corrosion resistance and low-temperature toughness the application needs.
Machining, Welding, and Additive Manufacturing
Fabrication is not where grade 5 and grade 23 diverge, but the differences are worth knowing before you quote a part.
Both grades are considered difficult to machine, with low thermal conductivity that concentrates heat at the cutting edge and a tendency to gall. Grade 23 is marginally easier to cut than grade 5 because its refined, lower-interstitial microstructure is slightly softer and more uniform, which can mean a small reduction in tool wear and a slightly better finish. Do not expect a dramatic difference. Budget for the same rigid setup, sharp tooling, and coolant discipline on both.
For welding, the ELI grade’s lower nitrogen and hydrogen improve weld soundness, and ELI-grade filler ERTi-23 (AWS A5.16, UNS R56401) is often used even when welding grade 5 base material for critical joints. Grade 23’s lower interstitial content also gives welded joints better ductility retention. For a full treatment of titanium welding, our grade 2 vs grade 5 titanium welding guide covers filler selection and shielding in detail.
Additive manufacturing is one area where grade 23 clearly leads. Grade 23 ELI powder is the default for medical laser powder-bed fusion, because a lower-oxygen starting powder translates to better finished-part toughness, and because implants printed layer by layer are porosity-sensitive.
As-built ELI parts carry residual stress and surface roughness that limit fatigue, so medical AM typically adds hot isostatic pressing (HIP) and machining to close pores and restore fatigue life. Peer-reviewed work comparing additively manufactured and wrought ELI for hip implants confirms that HIP and post-machining are what make printed implants mechanically competitive. If your part is headed for an implant printer, specify grade 23 ELI powder, not grade 5.
Cost: Is Grade 23 Worth the Premium?
Grade 23 costs more, and the premium is real. Plan for roughly 15-40% more per kg than grade 5, with typical quotes landing at 20-30%, or about $15-30/kg extra on common bar stock in 2026. Grade 23 ELI powder for additive manufacturing carries a similar margin.
The extra cost is not markup. Holding oxygen below 0.13% requires cleaner sponge, tighter melting control, and often double or triple vacuum arc remelting. Certification overhead adds more, since ASTM F136 and AMS 4930/4931 demand additional testing and full traceability documentation that commercial ASTM B348 does not. Supply is also more constrained, because fewer mills hold ELI certification.
Two things keep the premium in perspective. On a finished part, the material premium shrinks to roughly 10-25%, because machining time and tool wear dominate part cost.
The premium is also only worth paying when it buys something your design actually needs. For a fatigue-critical implant, a cryogenic tank, or a fracture-critical aircraft fitting, the 20-30% material premium is trivial next to the cost of a field failure. For a general-corrosion seawater bracket that never sees cyclic loading, grade 23 delivers no measurable benefit, and you are paying for chemistry you will never use.
An over-specification audit at an OEM we know caught exactly that. A pump bracket specified in grade 23 ELI ran identically in grade 5 after the corrosion environment was rechecked, and the switch cut material cost by about a quarter.
Where cost is the deciding factor across materials, our titanium vs stainless steel cost guide and the grade 2 vs grade 5 titanium cost comparison help you judge titanium against the alternatives.
Thinking about a stainless alternative for a non-implant corrosion application? DAPU supplies stainless steel in multiple grades and product forms, and our team can help you compare total cost against titanium for your service conditions.
Grade 5 vs Grade 23 Titanium: How to Choose
The choice between grade 5 and grade 23 comes down to the failure mode you’re designing against.
- Choose grade 5 (Ti-6Al-4V) when the design is strength-limited. General aerospace structures, fasteners, marine and industrial hardware, and non-implant medical instruments benefit from its higher strength and lower cost. If the part operates near yield but does not carry millions of fatigue cycles, grade 5 is the economical default.
- Choose grade 23 (Ti-6Al-4V ELI) when the design is damage-tolerance-limited. Permanent implants require ASTM F136 grade 23 by regulation. Cryogenic service, fracture-critical aerospace parts, and fatigue-limited components justify the premium because toughness and slow crack growth are the design drivers.
- When in doubt, follow the governing standard. If your print cites ASTM F136, ISO 5832-3, AMS 4930, or AMS 4931, you need grade 23 ELI, and nothing else will satisfy the paperwork. If it cites ASTM F1472 or commercial ASTM B348 with no ELI requirement, grade 5 is the intended material.
Before you order, verify the grade on the Mill Test Report. The alloy name is not proof. Oxygen must be at or below 0.13%, iron at or below 0.25%, and the standard and revision must match your print. A few minutes of verification at procurement prevents the kind of rejected heat that our spinal implant engineer caught at incoming inspection.
Frequently Asked Questions
What is the difference between grade 5 and grade 23 titanium?
Grade 5 (Ti-6Al-4V) and grade 23 (Ti-6Al-4V ELI) are the same alpha-beta alloy with tighter interstitial limits in grade 23. Grade 23 caps oxygen at 0.13% (vs 0.20% for grade 5) and iron at 0.25% (vs 0.40%), which raises fracture toughness, fatigue life, and cryogenic ductility while slightly lowering static strength.
Is grade 23 titanium the same as Ti-6Al-4V ELI?
Yes. Ti-6Al-4V ELI (Extra Low Interstitial) is the formal name for grade 23 titanium, UNS R56401. Grade 5 is standard Ti-6Al-4V, UNS R56400. The two share nominal chemistry but differ in interstitial impurity limits.
Is grade 23 titanium stronger than grade 5?
No. Grade 5 is slightly stronger, at about 895 MPa minimum tensile and 828 MPa minimum yield (annealed), versus about 860 MPa and 795 MPa for grade 23. Grade 23 deliberately trades about 4% of static strength for higher fracture toughness, ductility, and fatigue resistance.
What does ELI mean in titanium?
ELI means Extra Low Interstitial. It refers to tighter maximum limits on the interstitial elements oxygen, nitrogen, carbon, and hydrogen, plus iron. Lower interstitials, especially oxygen, improve fracture toughness and fatigue resistance at a small cost in strength.
Is grade 5 titanium acceptable for surgical implants?
For permanent load-bearing implants, no. Those require grade 23 ELI to ASTM F136 (or ISO 5832-3). Grade 5 to ASTM F1472 is acceptable for non-load-bearing and temporary medical hardware such as instruments, trial implants, spacers, and external fixation devices.
What is ASTM F136 titanium?
ASTM F136 is the specification for wrought Ti-6Al-4V ELI (grade 23) surgical-implant alloy, UNS R56401. Because the standard covers only the ELI chemistry, “Ti-6Al-4V per ASTM F136” always means grade 23.
Can grade 5 titanium be used in cryogenic service?
Standard grade 5 embrittles at cryogenic temperatures and is generally not specified for that service. Grade 23 ELI retains toughness down to about -253°C (liquid hydrogen) and is the grade used for cryogenic tanks, pressure vessels, and piping.
Why is grade 23 used for medical implants?
Grade 23 ELI offers the fatigue resistance, fracture toughness, and biocompatibility that permanent implants need to survive millions of in-vivo loading cycles. Its stable oxide layer resists corrosion in body fluids, and ASTM F136 makes it the required implant specification.
How much more does grade 23 titanium cost than grade 5?
Grade 23 typically costs 15-40% more per kg than grade 5, with most quotes at 20-30% (about $15-30/kg more on common bar). The finished-part premium is smaller, roughly 10-25%, because machining cost dominates.
Can stainless steel replace grade 23 titanium in medical hardware?
For non-implant medical hardware and instruments, often yes. 316/316L stainless steel resists corrosion and autoclave sterilization, welds easily, and costs far less than titanium. Implanted components that require ASTM F136 grade 23 titanium cannot be substituted with stainless.
Conclusion
Grade 5 vs grade 23 titanium is not a contest between a good alloy and a better one. Both are Ti-6Al-4V. The entire difference is interstitial chemistry: grade 23 holds oxygen to 0.13% and iron to 0.25%, trading about 4% of static strength for dramatically better fracture toughness, fatigue life, and cryogenic ductility.
The decision framework is simple. Specify grade 5 when peak strength and cost rule, and the part is not fatigue-critical, implanted, or cryogenic. Specify grade 23 ELI when the governing standard demands it, which is the case for permanent implants under ASTM F136, for cryogenic service, and for fracture-critical aerospace parts bought to AMS 4930 or 4931. Verify the Mill Test Report before you accept delivery, because the alloy name alone never confirms the grade.
For help selecting the right material for your project, contact LIANYUNGANG DAPU METAL for material selection guidance or request a quote. If your application is corrosion-driven rather than fatigue-driven, our engineers can also help you weigh the stainless steel alternatives that cover most industrial and instrument service at a fraction of titanium’s cost.
