ASTM F136 — Wrought Ti-6Al-4V ELI for Medical Implants
Complete guide to ASTM F136 specification for wrought Ti-6Al-4V ELI (Grade 23) titanium alloy for surgical implant applications. Chemical composition, mechanical properties, and certification requirements for medical-grade titanium.
Quick Answer
What is ASTM F136?
ASTM F136 is the specification for wrought Ti-6Al-4V ELI (Extra Low Interstitial) titanium alloy intended for surgical implant applications. It defines tighter chemical composition limits than ASTM B348, with reduced oxygen (≤ 0.13%), iron (≤ 0.25%), and hydrogen (≤ 0.012%) to improve fracture toughness and fatigue resistance. ASTM F136 is the most widely specified material standard for orthopaedic and dental implant manufacturing worldwide.
Scope
ASTM F136 covers wrought Ti-6Al-4V ELI (Grade 23) in the form of bars, wire, forgings, and rings for surgical implant applications. The standard applies to material in the annealed condition, with additional heat treatment options available to meet specific implant design requirements.
Key parameters covered:
- Forms: Bar, wire, forging stock, and ring-rolled products
- Condition: Annealed (standard); solution-treated and aged (optional)
- Dimensions: As specified by the implant manufacturer
- Microstructure: Equiaxed alpha-beta, fine grain size
Key Requirements
Chemical Composition (ASTM F136 vs ASTM B348 comparison)
| Element | ASTM F136 (Max %) | ASTM B348 Grade 23 (Max %) |
|---|---|---|
| Aluminium | 5.50–6.50 | 5.50–6.50 |
| Vanadium | 3.50–4.50 | 3.50–4.50 |
| Iron | ≤ 0.25 | ≤ 0.25 |
| Oxygen | ≤ 0.13 | ≤ 0.20 |
| Carbon | ≤ 0.08 | ≤ 0.08 |
| Nitrogen | ≤ 0.05 | ≤ 0.05 |
| Hydrogen | ≤ 0.012 | ≤ 0.015 |
The tighter oxygen and hydrogen limits are the defining characteristics of F136 material, providing superior fracture toughness for implant applications.
Mechanical Properties
| Property | Requirement (Annealed) |
|---|---|
| Tensile Strength | 860 MPa (min) |
| Yield Strength (0.2% offset) | 795 MPa (min) |
| Elongation | 15% (min) |
| Reduction of Area | 35% (min) |
| Fracture Toughness (K₁c) | 75 MPa√m (typical) |
Microstructure Requirements
- Fine-grained, equiaxed alpha-beta microstructure
- No continuous alpha network at prior beta grain boundaries
- No evidence of gross segregation or inhomogeneity
- Grain size: ASTM No. 6 or finer for bar under 50 mm diameter
Testing & Certification Requirements
- Mechanical testing — Per ASTM E8/E8M at room temperature
- Chemical analysis — Per ASTM E120, E2371, or equivalent
- Microstructure evaluation — Per ASTM E3 and E407 at 100× and 500×
- Ultrasonic inspection — Per ASTM E213 or E2375 for implant-grade material
- Tensile and bend testing — On each heat/lot
- Certification — Full MTR with chemical, mechanical, and microstructural data
Typical Applications
- Orthopaedic Implants: Hip stems, acetabular cups, femoral components, tibial trays, trauma plates, bone screws, spinal fixation rods and pedicle screws
- Dental Implants: Abutments, implant bodies, healing caps, bar attachments
- Surgical Instruments: Drill guides, bone cutting guides, reamers, implant insertion tools
- Craniofacial: Mandibular plates, cranial mesh, orbital floor implants
- Cardiovascular: Pacemaker housings, ventricular assist device components
Related Materials
- Grade 23 Titanium (Ti-6Al-4V ELI) — The exact alloy specified by ASTM F136
- Grade 5 Titanium (Ti-6Al-4V) — Higher oxygen version, not suitable for implant use per ASTM F136
- ASTM F1472 (Ti-6Al-4V) — Alternative standard for wrought Ti-6Al-4V for surgical implants (standard interstitial level)
Related Services
- 5-Axis CNC Machining — Complex implant geometries (hip stems, spinal cages) from F136 bar or billet
- CNC Turning — Precision cylindrical implant components (screw blanks, abutments)
- Wire EDM — Cutting of implant blanks with minimal heat-affected zone
- Additive Manufacturing (DMLS) — Custom patient-specific implants from F136 powder
- Surface Finishing — Electropolishing, passivation, and bead blasting per ASTM F86