Ti-6Al-4V vs Ti-6Al-4V ELI (Grade 5 vs Grade 23)

Updated October 13, 2026

One alloy, two interstitial budgets

Grade 5 and Grade 23 have the same nominal composition, 6 percent aluminum and 4 percent vanadium. The difference is how much oxygen, iron, nitrogen and hydrogen the mill is allowed to leave in. Those interstitial and residual elements raise strength and cost ductility and toughness, so the ELI grade trades a little strength for a material that tolerates cracks, welds and cold better.

ATI's technical data sheet for its Grade 23 product (version 1, February 2012) describes it as a higher purity grade with lower oxygen, carbon and iron, the preferred grade for marine and cryogenic applications, and used in some important aerospace components. United Performance Metals' 2026 data sheet says the reduced interstitials enhance fracture toughness, fatigue strength and ductility compared with the standard grade. Neither document gives design allowables, and neither should be used as one.

Watch the UNS numbers on certs. ASTM F136, the implant specification, covers ELI as UNS R56401, while ATI lists its Grade 23 product as UNS R56407. A cert can be correct and still name a different UNS number than your drawing, so the procurement spec, not the UNS number, is what to check.

This page compares the two grades. General titanium practice, including alpha case, CP grades and Ti-6-2-4-2, is on the titanium alloys page.

Side-by-side: chemistry limits and strength minimums

The short version is oxygen 0.20 versus 0.13 percent maximum and iron 0.40 versus 0.25 percent maximum, which buys toughness at the cost of about 10 ksi of minimum ultimate and yield. Values below are ASTM B348 bar limits as published in supplier summaries of the standard, plus producer typical values where labeled. AMS documents set their own limits by product form, so read the spec your drawing names.

The beta transus row comes from two producers, so treat the 40 F gap as indicative rather than measured on the same heat. It still matters in practice: oxygen is an alpha stabilizer, so a heat treater who sets furnace temperatures from Grade 5 habit is working closer to the transus on ELI than they may think. Ask for the transus of the actual heat when a process runs near it.

Toughness, cryogenic use and fracture critical parts

ELI is chosen for toughness, not strength. Lower oxygen and iron leave a more ductile alpha phase, and the benefit shows most at low temperature, where interstitial-rich titanium loses ductility. That is why producers list Grade 23 for cryogenic service, and why cold hardware such as propellant tank fittings is a typical ELI application.

For fracture critical and damage tolerant designs, the relevant number is fracture toughness, because a tougher material tolerates a larger crack at the same stress before it fails. That changes inspection intervals and the flaw size NDT must find. We do not quote cryogenic toughness values here: neither the ATI nor the UPMET data sheet publishes them, and design values belong in your program's allowables source or in mill test data for the actual heat. If toughness is a requirement, put it on the PO. AMS 4931, whose title covers ELI bars, forgings and rings in the duplex annealed condition with fracture toughness, is the bar and forging specification written for that case.

Welding is where the grade difference is easiest to see. ATI states that ductility, impact strength and fracture toughness of Grade 23 welds are significantly better than welds of the standard grade. For welded pressure hardware, ELI base metal is often the simplest way to keep weld zone toughness acceptable.

The ELI advantage is not permanent. ATI warns that hydrogen pickup during improper pickling and oxygen, nitrogen and carbon pickup during forging, heat treating and brazing degrade ductility. A part machined from ELI bar and then heat treated in a poor vacuum may no longer have ELI properties at its surface. Flow the atmosphere requirements to every processor, and ask for the hydrogen check the spec requires after chemical processing.

Choose Grade 5 when, choose Grade 23 when

Default to Grade 5 unless toughness, temperature or weld quality is what limits the design.

• Choose Grade 5 when the part is strength or stiffness limited at room or moderate temperature: brackets, fittings, housings, fasteners and machined structure that is not on a fracture critical list.
• Choose Grade 5 when you may need solution treating and aging for extra strength; ATI notes Grade 23 is normally used annealed.
• Choose Grade 5 when lead time matters more than toughness margin and the ELI form and size you need is not readily available; ask for both grades at quote.
• Choose Grade 23 when the part is designated fracture critical or analyzed for damage tolerance and the analysis needs the higher toughness.
• Choose Grade 23 when the part runs at cryogenic temperature, such as propellant tank fittings and cold fluid line hardware.
• Choose Grade 23 when a welded joint carries significant load and weld toughness is limiting.
• Choose Grade 23 when the part is an implant or surgical device, where ASTM F136 governs.

One trap: ELI material always satisfies Grade 5 chemistry, but not always Grade 5 strength minimums. Substituting ELI for Grade 5 needs engineering approval like any other change, because 110 ksi minimum yield does not meet a 120 ksi requirement.

Procurement specifications by form

Name the AMS specification by product form; the grade alone is not a procurement requirement. The table lists the specifications most often seen on aerospace drawings for each grade. Confirm the current revision on ASSIST or SAE before ordering.

F136 material is made for the medical market, and distributor ELI data sheets often list F136 properties next to AMS 4930. It is a different document from AMS 4930. If your drawing calls AMS 4930, an F136-only cert does not meet it, even if the chemistry would. Ask whether the heat is certified to the AMS specification and require that specification on the cert. For how to read the cert itself, see material certs and traceability.

Additive manufacturing: ASTM F2924 vs ASTM F3001

The same split exists for powder bed fusion. ASTM F2924 covers additively manufactured Ti-6Al-4V by full-melt powder bed fusion, electron beam or laser, and ASTM F3001 covers the ELI version. ASTM lists F2924-14(2021) and F3001-14(2021) as active. Both cover feedstock, the manufacturing plan, chemistry, microstructure, mechanical properties, thermal processing and hot isostatic pressing, and F3001 points to the supplementary requirements in F2924 for buyers who need tighter controls. ASTM F3301 covers thermal post-processing for both grades.

The practical difference for AM is the oxygen margin. Titanium powder picks up oxygen through handling and reuse, and the ELI limit of 0.13 percent leaves much less room than 0.20 percent. If you call F3001, require the oxygen result on the finished build or witness coupon, not only on the virgin powder lot, and ask how the builder controls powder reuse. Program requirements such as NASA-STD-6030 sit on top of the ASTM material spec; see metal additive manufacturing and our additive sourcing page.

Availability and cost drivers

ELI usually costs more and is thinner in stock, for reasons that follow from the chemistry. These are qualitative drivers; we do not publish prices.

• Feedstock. Low oxygen and low iron limits restrict which sponge and revert a mill can charge, which narrows the raw material.
• Melting. ATI produces its Grade 23 by vacuum arc primary melting followed by a second vacuum arc remelt; specifications set the melt practice for each grade.
• Market split. ELI serves the implant market under ASTM F136 as well as aerospace; UPMET's ELI data sheet leads with medical implant uses. A heat certified only to F136 does not satisfy an AMS callout, which limits what an aerospace buyer can accept.
• Form and size gaps. Stocking ranges are narrower than for Grade 5. As one example, UPMET's 2026 data sheet lists ELI plate from 0.250 to 1.000 in and bar from 0.125 to 3.000 in.
• Testing. A fracture toughness requirement, such as AMS 4931 material, adds tests and time.
• Specialty metals. Both grades are titanium alloys and fall under DFARS 252.225-7009 on defense work; see DFARS specialty metals.

When ELI plate or bar in the needed size is not available, the usual options are a larger size and more machining, a forging, or a different product form under the matching ELI specification. Each changes cost and lead time, so raise the question at quote rather than at receipt.

Machining, forming and heat treatment differences

The two grades machine almost identically. ATI recommends practices similar to austenitic stainless steel for Grade 23: slow speeds, heavy feeds, rigid tooling and plenty of non-chlorinated cutting fluid. The lower strength of ELI is not enough to change feeds and speeds in a meaningful way, and the titanium-specific practices on the titanium alloys page apply to both.

Forming is where ELI helps. ATI states Grade 23 forms better than the standard grade, though it is still difficult to form at room temperature annealed, and that severe forming of annealed material can be done at up to 1200 F without affecting properties. Hot sizing by creep forming is done between 1000 and 1200 F.

Heat treatment is simpler for ELI because it is normally used annealed. ATI lists an anneal of 1300 to 1350 F for 1 to 8 hours, air cool, and stress relief at 900 to 1200 F for 1 to 4 hours. Aging ELI to reach Grade 5 strength defeats the reason for buying it. Heat treat to the processing spec on the drawing, in vacuum or inert atmosphere, with alpha case removal verified; see heat treatment.

Callout examples for the drawing and PO

State the grade, the specification by form, the condition and anything the specification does not already cover. Adapt these examples; they are not a substitute for your program's drawing standards.

• Standard grade plate: MATERIAL: TITANIUM ALLOY 6AL-4V, ANNEALED, PLATE PER AMS 4911.
• ELI bar: MATERIAL: TITANIUM ALLOY 6AL-4V ELI, ANNEALED, BAR PER AMS 4930. SUBSTITUTION OF STANDARD GRADE NOT PERMITTED.
• Fracture critical ELI: MATERIAL: TI-6AL-4V ELI, DUPLEX ANNEALED, PER AMS 4931, INCLUDING FRACTURE TOUGHNESS TESTING PER THE SPECIFICATION. PART IS FRACTURE CRITICAL; TRACEABILITY TO HEAT REQUIRED.
• AM part: MATERIAL: TI-6AL-4V ELI BY POWDER BED FUSION PER ASTM F3001, CLASS AS DEFINED IN F3001, HIP AND THERMAL PROCESSING PER THE SPECIFICATION AND APPROVED PART PLAN.

On the PO, require:

• A mill cert showing actual oxygen, iron, nitrogen, carbon and hydrogen, tensile results and the heat number, against the exact specification and revision on the drawing.
• Melt source and country, for DFARS specialty metals.
• Every downstream processor's cert, with the hydrogen result after any pickling or etching.
• No substitution between grades or specifications without written approval.

Get Grade 5 or ELI material and parts quoted

The usual failure on ELI jobs is paperwork: an implant-grade cert against an AMS callout, a missing toughness test or a processor who never saw the atmosphere requirement. Send your requirement through a certified material quote request and we will source the grade and form from mill-certified stock, check the cert against your specification before anything ships, and flow down processing requirements when the material becomes a machined part. Related pages: materials hub, certified aerospace material, bar and rod and Inconel 718 vs 625.

Questions

Related

• Titanium Alloys for Aerospace Hardware
• Metal Additive Manufacturing for Aerospace Hardware
• Material Certs, Specialty Metals and Lot Traceability
• Inconel 718 vs Inconel 625

Sources

• ATI, ATI 6-4 ELI (Ti-6Al-4V ELI, Grade 23) technical data sheet, version 1, February 2012
• United Performance Metals, Ti-6Al-4V ELI data sheet (2026)
• United Performance Metals, Ti-6Al-4V data sheet (AMS 4911, 4928)
• GS Alloy, ASTM B348 titanium bars and billets, chemistry and properties summary
• Performance Titanium, ASTM B348 Grade 23 summary
• SAE AMS 4907, Titanium Alloy Sheet, Strip, and Plate, 6Al-4V, Extra Low Interstitial, Annealed
• Titanium Industries, AMS 4930 specification summary
• DIN Media, SAE AMS 4931, Ti-6Al-4V ELI bars, forgings and rings, duplex annealed, fracture toughness
• SAE AMS 4928, Titanium Alloy Bars, Forgings, and Rings, 6Al-4V Annealed
• ASTM F136, Wrought Ti-6Al-4V ELI Alloy for Surgical Implant Applications (UNS R56401)
• ASTM F2924, Additive Manufacturing Ti-6Al-4V with Powder Bed Fusion
• ASTM F3001, Additive Manufacturing Ti-6Al-4V ELI with Powder Bed Fusion
• DFARS 252.225-7009 specialty metals