Mechanical Properties of Grade 5 Titanium (Ti-6Al-4V): Complete Reference

What Is Grade 5 Titanium?

Grade 5 titanium, designated Ti-6Al-4V and UNS R56400, is an alpha-beta titanium alloy containing about 6% aluminum and 4% vanadium. The specified ranges per ASTM B348 are aluminum 5.5-6.75% and vanadium 3.5-4.5%. Aluminum stabilizes the alpha phase and raises strength and creep resistance, while vanadium stabilizes the beta phase, improving hot workability and enabling heat treatment. Grade 5 accounts for roughly half of all titanium consumed worldwide because it delivers the best practical balance of strength, weight, corrosion resistance and fabricability for engineering components.

Key Mechanical Properties at a Glance

The table below summarizes the room-temperature mechanical properties of annealed Grade 5 titanium bar, plate and forgings, which is the reference condition for most design work. Material is commonly supplied to ASTM B348 (bar), ASTM B265 (plate and sheet) or AMS 4911 (aerospace plate).

Annealed values are the correct reference for procurement. After solution treatment and aging, tensile strength can rise above 1100 MPa, but ductility and fracture toughness decrease. Beta annealing improves fracture toughness at some expense of ultimate strength, so the heat-treatment route should be matched to the service requirement.

Strength, Hardness and Heat Treatment

Tensile and yield strength are the first properties buyers check. For annealed bar, the ASTM B348 minimum tensile strength is 895 MPa and the minimum yield strength is 828 MPa; typical mill material tests in the range of 950 MPa tensile and 880 MPa yield with 12-14% elongation. Hardness is typically 30-36 HRC, which gives good resistance to wear and local deformation in threaded fasteners, bushings and bearing surfaces. In the STA condition, hardness can reach the upper 30s HRC, which is why aerospace fasteners and high-load fittings are commonly specified in the solution-treated and aged condition.

Because Grade 5 is an alpha-beta alloy, its final properties depend on processing history. A fine, equiaxed alpha-plus-beta microstructure from mill annealing gives the best combination of strength and ductility, while a Widmanstatten structure from beta processing improves creep and fracture toughness for high-temperature service.

Corrosion Resistance of Grade 5 Titanium

Grade 5 titanium resists corrosion because it forms a stable, self-repairing oxide film in the presence of oxygen or water. The film makes the alloy resistant to seawater, oxidizing acids, chloride solutions and most industrial atmospheres, so coated or painted protection is rarely needed. In marine environments, Ti-6Al-4V is essentially immune to pitting and stress corrosion cracking, which explains its long service life in offshore equipment and seawater heat exchangers. The main limitations are reducing acids, hydrofluoric acid and fluoride-containing media, where the passive film breaks down; these conditions require corrosion testing before selection.

Welding and Fabrication

Welding Grade 5 titanium demands strict shielding because the alloy reacts with oxygen, nitrogen and hydrogen above roughly 500 C, embrittling the weld. Gas tungsten arc welding (GTAW) with trailing and back shielding of high-purity argon, or electron beam welding in vacuum, are the standard processes. Heat input must be controlled to minimize the heat-affected zone and avoid alpha-case formation. Filler metal per AWS A5.16 (ERTi-5) is used for matching composition. With modern equipment, laser welding and additive manufacturing are also used to produce complex Ti-6Al-4V components for aerospace and medical applications.

Typical Applications

Aerospace: airframe structures, landing-gear components, engine parts such as blades and discs, fasteners

Medical: surgical instruments and non-implant devices; permanent implants normally use the extra-low-interstitial Grade 23 variant per ASTM F136

Automotive and motorsport: valves, connecting rods, suspension springs, exhaust components

Marine and offshore: propeller shafts, seawater pump components, subsea hardware

Chemical processing: pumps, valves, heat exchanger tubes and vessels in chloride service

Sporting goods: bicycle frames, golf club heads, diving equipment

Frequently Asked Questions

1. Is Grade 5 titanium stronger than Grade 2 commercially pure titanium?

Yes. Grade 5 has a minimum tensile strength of 895 MPa per ASTM B348, roughly three times the 345 MPa minimum of annealed Grade 2. The trade-off is lower ductility and formability, so Grade 2 remains preferred where cold forming dominates.

2. What is the tensile strength of annealed Ti-6Al-4V?

Typically 895-950 MPa for annealed bar and plate, with a minimum of 895 MPa per ASTM B348. After solution treatment and aging, values above 1100 MPa are achievable.

3. Can Grade 5 titanium be heat treated?

Yes. Solution treatment followed by aging increases strength and hardness, while annealing restores ductility. Beta annealing improves fracture toughness. Heat treatment must follow qualified cycles because response depends on section size and prior processing.

4. Why is Grade 5 titanium used in medical devices but not always in implants?

Grade 5 is biocompatible and widely used in surgical instruments and trauma devices. For permanent implants, the ELI version (Grade 23, UNS R56401) is preferred because lower oxygen content improves fracture toughness and fatigue resistance in the human body.

5. How does the density of Grade 5 compare with steel?

Grade 5 titanium has a density of 4.43 g/cm3, about 56% of steel's 7.85 g/cm3. A Ti-6Al-4V part can therefore weigh roughly half as much as an equally sized steel part while offering comparable or higher strength.

6. Does Ti-6Al-4V corrode in seawater?

No. The passive oxide film makes it effectively immune to general corrosion, pitting and crevice attack in seawater at service temperatures. It is a standard material for marine shafts, heat exchangers and offshore components.