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

metal

titanium alloy — alpha-beta (extra low interstitial)

Ti64 ELIGrade 23 TitaniumUNS R56401Ti-6Al-4V ELIASTM F136 Ti alloyMedical Grade Ti64

Ti-6Al-4V ELI (Grade 23) 3D printed component

Density

4.43 g/cm³

YS (LPBF as-built (XY))

930–1120 MPa

UTS (LPBF as-built (XY))

1050–1280 MPa

Elongation (LPBF as-built (XY))

5.0–13.0 %

Elastic modulus

105–120 GPa

Thermal conductivity

6.7 W/m·K

Composition — UNS R56401 / ASTM F3001-14 / ASTM F136

Element	Min %	Max %	Notes
Ti	bal.		balance
Al	5.50	6.500	Alpha stabiliser; narrows range vs. Grade 5 (5.5–6.75) for tighter microstructure control
V	3.50	4.500
Fe	—	0.250	Reduced from 0.30% (Grade 5) — Fe is a beta stabiliser that affects transformation behaviour
O	—	0.130	Key interstitial — primary driver of ductility and fracture toughness improvement vs. Grade 5. Oxygen strengthens but embrittles; ELI reduces O limit from 0.20% to 0.13%.

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Mechanical & thermal properties — 4 conditions

Property	LPBF as-built (XY)	LPBF annealed (700–800°C / 2h / AC) (XY)	LPBF + HIP (920°C / 100 MPa / 2h)	EBM as-built
Elastic modulus	105–120 GPa	—	—	—
Yield strength (0.2%)	930–1120 MPa	759–1000 MPa	780–930 MPa	760–920 MPa
Ultimate tensile strength	1050–1280 MPa	860–1050 MPa	860–1010 MPa	860–1000 MPa
Elongation at break	5.0–13.0 %	10.0–20.0 %	13.0–24.0 %	12.0–21.0 %
Hardness (HV)	—	295–355 HV10	—	—
Fatigue strength	—	480–680 MPa	620–820 MPa	—
Fracture toughness KIC	—	60.0–95.0 MPa√m	72.0–110.0 MPa√m	—
Density	4.43 g/cm³	—	—	4.43 g/cm³
Relative density	99.0–100.0 %	—	—	—
Thermal conductivity	6.7 W/m·K	—	—	—
CTE	8.4–9.0 µm/m·K	—	—	—
As-built surface Ra	—	—	—	20.0–45.0 µm

Values shown as min–max where a spread is reported, otherwise as typical ± unit. Ranges reflect inter-source variation, not single-sample scatter. All values are for AM-processed specimens unless noted.

Engineering considerations

Implant qualification pathway (US): ASTM F3001 for powder and part properties, FDA AM Guidance 2017 for 510(k)/PMA submission. Device-level testing (ISO 7206 for hip, ASTM F3141 for spine, ISO 14801 for dental) is required regardless of material compliance.
EBM for orthopaedics: lattice design for osseointegration should target pore size 300–600 µm and porosity 50–70% — these values are empirically proven for bone ingrowth. EBM Arcam A2XX series is the dominant platform for orthopaedic Ti-6Al-4V ELI.
LPBF for medical: stress relief (600°C/2h in vacuum) plus solution anneal (730–800°C/2h, furnace cool) is the standard post-processing route for LPBF ELI implants. HIP (920°C/100 MPa/2h) adds cost but is justified for fracture-critical spinal implants.
Anisotropy consideration: for spinal cages loaded in axial compression (primary load), the Z-direction (lowest LPBF strength) is aligned with the loading axis — design for worst-case Z-direction properties unless post-HT restores isotropy.
Wear surfaces: Ti-6Al-4V ELI is unsuitable as a bearing surface without modification. For modular neck tapers and femoral head interfaces, specify: (a) PVD TiN coating (HV 2000, Ra < 0.1 µm), (b) anodised TiO₂ (corrosion protection), or (c) mate with UHMWPE, CoCrMo ceramic, or alumina.
Sterilisation compatibility: steam autoclave (134°C, compatible), gamma irradiation (25 kGy, compatible), EtO (compatible). Select final finish before sterilisation — passivation per ASTM F86 recommended before gamma or EtO sterilisation.
Osseointegration surface design: as-built EBM surfaces (Ra 20–35 µm) provide excellent primary fixation. Further roughening via grit blasting or acid etching is used when Ra > 35 µm osseointegration texture is desired. Do not polish osseointegration surfaces.
Regulatory note: EU MDR 2017/745 Class III (implantable devices) requires Notified Body involvement. Clinical evaluation and post-market follow-up are mandatory in addition to material and device testing.

Advantages

Biocompatible — ASTM F136 / ISO 5832-3 certified; no cytotoxicity, genotoxicity, or immunogenicity concerns for long-term implantation
Superior fracture toughness vs. Grade 5 — KIC ~80–90 MPa√m vs. ~55–70 MPa√m — critical for fracture-critical implants
Better fatigue crack growth resistance — lower crack propagation rate in body fluid environment vs. Grade 5
Meets ASTM F3001 property minimums as-built after EBM — simplifies implant qualification pathway
EBM enables porous osseointegration structures and solid regions in a single build — no assembly
Elastic modulus (110–115 GPa) closer to cortical bone (10–30 GPa) vs. cobalt chrome (200 GPa) — reduces stress shielding
Excellent corrosion resistance in body fluids — passive TiO₂ film is stable in saline, pH 5–9, and plasma

Limitations

Lower yield and UTS than Grade 5 — ~10% less strength due to lower O content. Acceptable for most implant designs but requires awareness in structural analysis
LPBF as-built elongation (5–8%) insufficient for implant standards — annealing mandatory for LPBF medical applications
Poor wear resistance — Ti alloys are not suitable for bearing surfaces without coating (TiN, TiO₂) or ceramic insert
Extremely high cost — ELI grade powder is typically 20–40% more expensive than Grade 5 powder
EBM surface roughness (Ra 20–45 µm) — bearing surfaces require machining to Ra < 0.1 µm; adds cost and setup complexity
Titanium is MRI compatible but causes imaging artefacts — plan implant orientation to minimise diagnostic shadow
No published AM ELI fatigue endurance standard — each implant design requires device-level fatigue testing to ISO 7206, ASTM F1800, or equivalent
Powder handling: same ATEX/OSHA requirements as Grade 5; ELI powder must be handled in inert atmosphere due to fine particle reactivity

Typical applications

Total hip arthroplasty — femoral stems and acetabular cups with porous lattice for osseointegration (EBM)Total knee arthroplasty — tibial trays and augments with porous ingrowth structures (EBM)Spinal interbody fusion cages — PLIF, TLIF, ALIF cages with porous scaffold for bone growth through implantDental implants and abutments — patient-specific and standard prosthetic implantsTrauma implants — bone plates, screws, and intramedullary nails (fracture-critical → ELI preferred over Grade 5)Patient-specific implants (PSI) — craniofacial, maxillofacial, mandibular reconstructionSurgical instruments requiring biocompatibility and sterilisabilityAerospace fracture-critical brackets and fittings where KIC is the design driver

Standards & certifications

ASTM-F3001established

Ti-6Al-4V ELI parts produced by powder bed fusion (LPBF and EBM) — defines composition, powder, and minimum mechanical property requirements for the ELI grade

medicalaerospace

The primary AM standard for ELI grade. Mechanical property minimums are equivalent to wrought ASTM F136 — this enables AM implant qualification using the same acceptance criteria as wrought.

ASTM-F2924established

Grade 5 Ti-6Al-4V — referenced for comparison; ELI grade (F3001) has lower property minimums due to reduced interstitial content

aerospacedefence

ISO-5832-3established

Wrought Ti-6Al-4V reference standard for implant property comparison

medical

Wrought ELI reference. AM ELI implants must also satisfy FDA AM Guidance 2017 (US) or EU MDR Annex II (Europe).

ISO-13485established

Medical device quality management system — required for implant manufacturers

medical

ISO-10993-1established

Biocompatibility evaluation framework — required for all implantable AM devices

medical

FDA-AM-GUIDANCE-2017established

FDA guidance for AM medical devices — submission requirements for 510(k) and PMA

medical

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

Composition — UNS R56401 / ASTM F3001-14 / ASTM F136

Mechanical & thermal properties — 4 conditions

Engineering considerations

Advantages

Limitations

Typical applications

Industries

Standards & certifications

Compatible AM processes (4)

Other metal materials

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