Two Grades, One Alloy System, Different Safety Margins

Both grades belong to the Ti-6Al-4V alloy system with nearly identical nominal compositions: approximately 6% aluminum, 4% vanadium, and the balance titanium. The performance difference stems from interstitial element control.

TC4 allows oxygen up to 0.20% and iron up to 0.40%, providing high strength with good ductility. TC4 ELI reduces oxygen below 0.13% and limits iron to within 0.25%, enhancing fracture toughness and damage tolerance while maintaining high mechanical strength.

TC4 emphasizes high strength, while TC4 ELI focuses on enhanced fracture toughness and damage tolerance. The key to selection lies in prioritizing strength versus damage tolerance under specific service conditions.

Aerospace Industry

TC4: The Classic Choice
Parts machined from TC4 bar are used throughout aircraft load-bearing areas — fuselage frames, wing joints, engine mounts, and fasteners. With a density of ~4.5 g/cm³ and tensile strength ≥895 MPa, its specific strength far exceeds that of high-strength steels and aluminum alloys. It maintains excellent mechanical performance in elevated-temperature aerospace applications, typically up to 300°C depending on design requirements.

Aerospace TC4 bars typically comply with AMS 4928 or customer specifications, requiring full heat treatment records, mechanical property reports, and ultrasonic inspection. Aerospace customers may require suppliers and subcontractors to adhere to Nadcap-controlled special processes, including heat treatment and NDT.

TC4 ELI: The Damage-Tolerant Upgrade
TC4 ELI is selected for aerospace applications requiring enhanced fracture toughness or low-temperature performance, where design prioritizes crack growth resistance and damage tolerance. Both grades are available; procurement must follow the standard specified on the part drawing.

Medical Sector: ASTM Grade 23 Titanium Bar for Medical Use

Load-bearing orthopedic implants — bone plates, spinal systems, hip stems, knee components — endure millions of loading cycles. Any internal defect can propagate, leading to implant fracture.

TC4 ELI's lower oxygen content reduces interstitial strengthening, enhancing ductility and fracture toughness. In the corrosive environment of body fluids, ELI's advantages become particularly evident. Typical applications include spinal pedicle screws, hip stems, bone plates, and dental abutments.

Regulations and Standards:Medical TC4 ELI bar must meet ASTM F136 (Ti-6Al-4V ELI wrought alloy for surgical implants) or ISO 5832-3. These standards have similar requirements but should not be considered identical without verification. Medical device manufacturers may select ASTM F136 or ISO 5832-3 depending on regulatory pathway and customer requirements. The material supplier provides heat number traceability, EN 10204 certificates, and compliance statements. The device manufacturer bears ultimate responsibility for final product compliance, including biocompatibility verification and ISO 13485 quality system requirements.

Oil & Gas Industry

Downhole tools—MWD housings, packer mandrels, safety valve components—are exposed to high pressures, sour media, cyclic stresses, and temperatures of 150–200°C. TC4 offers higher specific strength than most corrosion-resistant alloys and superior corrosion resistance compared to high-strength steels. Titanium alloys may be considered for sour service after evaluation per NACE MR0175/ISO 15156, based on H₂S partial pressure, temperature, pH, and chloride concentration.

Standard TC4 is the mainstream choice for downhole tools. TC4 ELI appears only occasionally in specialized tools requiring higher fracture toughness and is far less common. Oil & gas buyers prioritize NACE compliance and elevated-temperature performance over ELI-grade control.

Grade 5 vs. Grade 23 Titanium Bar Comparison

Typical minimum values for annealed bars; actual values depend on the applicable standard and product form.

Application Decision Quick Reference:

Frequently Asked Questions

Q1: Can TC4 and TC4 ELI be used interchangeably?
Not recommended. TC4 ELI provides superior fracture toughness and damage tolerance. The two materials have fundamentally different safety characteristics; procurement must comply with drawing and standard requirements.

Q2: TC4 or TC4 ELI for aerospace fasteners?
Most use TC4. TC4 ELI is selected only when the design explicitly requires it for damage-tolerant applications.

Q3: Is ELI required for all medical implants?
For load-bearing orthopedic implants, ASTM F136 (ELI) is the mainstream choice. Non-load-bearing devices may use commercially pure titanium (ASTM F67). The device manufacturer bears full compliance responsibility.

Q4: Can TC4 be used in sour oil and gas environments?
Titanium alloys may be considered for sour service after NACE MR0175/ISO 15156 evaluation, but applicability must be confirmed based on specific H₂S partial pressure, temperature, pH, and chloride concentration.

Q5: Can you supply TC4 and TC4 ELI bars? What are the lead times?
We supply TC4 and TC4 ELI bars per ASTM B348, ASTM F136, AMS standards, and customer requirements. Available in hot-rolled and forged forms with cut-to-length processing. Standard specifications are available immediately; custom production depends on dimensions and quantity.

Conclusion

TC4 and TC4 ELI represent two optimization directions: strength versus toughness. The choice depends on prioritizing either strength or damage tolerance based on service conditions.

We support ASTM B348 Grade 5, ASTM F136 Grade 23, and AMS specifications, offering custom precision titanium bars for Swiss-type CNC machining in aerospace, medical, and industrial applications.

[Send us your specifications to receive a TC4/TC4 ELI technical proposal and quote]

(Yucheng Hai Titanium | Precision Titanium Bar Supplier | TC4 / Grade 5 / TC4 ELI / Grade 23 |yuchenghaicompany.com)