Ti-6Al-4V, also known as Grade 5 titanium alloy, is one of the most popular titanium alloys used in a variety of applications. This article provides a comprehensive overview of Ti-6Al-4V, including its composition, properties, applications, specifications, pricing, handling and more.
Ti-6Al-4V Composition
Ti-6Al-4V is an alpha-beta titanium alloy containing 6% aluminum, 4% vanadium, 0.25% (maximum) iron, 0.2% (maximum) oxygen, and the remainder titanium. Here is the nominal composition of Ti-6Al-4V:
| Element | Weight % |
|---|---|
| Titanium | Balance |
| Aluminum | 5.5 – 6.75 |
| Vanadium | 3.5 – 4.5 |
| Iron | ≤ 0.3 |
| Oxygen | ≤ 0.2 |
The aluminum stabilizes and strengthens the alpha phase, while vanadium enables beta phase formation. The combination of alpha and beta phases gives Ti-6Al-4V excellent strength, corrosion resistance and workability.
Ti-6Al-4V Properties
Ti-6Al-4V has the following properties that make it advantageous for aerospace, medical, marine and other applications:
| Property | Value |
|---|---|
| Density | 4.43 g/cm3 |
| Melting Point | 1604 – 1660°C |
| Tensile Strength | 895 – 1170 MPa |
| Yield Strength | 825 – 1103 MPa |
| Elongation | 8 – 16% |
| Elastic Modulus | 114 GPa |
| Fatigue Strength | 400 – 500 MPa |
| Fracture Toughness | 55 – 115 MPa-m^1/2 |
| Corrosion Resistance | Excellent |
| Bio-compatibility | Excellent |
Key features:
- Lightweight with high strength-to-weight ratio
- Withstands extreme temperatures
- High fatigue strength
- Resistant to corrosion, acids, chlorides
- Compatible for implants and prosthetics
Ti-6Al-4V Applications
Ti-6Al-4V is used in the following major applications because of its unique combination of properties:
| Industry | Applications |
|---|---|
| Aerospace | Aircraft engine components, airframes, fasteners, hydraulic systems |
| Biomedical | Surgical implants, orthopedic and dental prosthetics |
| Marine | Propellers, offshore platform rigs, pipelines, heat exchangers |
| Chemical | Tanks, pipes, valves, pumps, reaction vessels |
| Automotive | Valves, connecting rods, suspension springs |
| Power generation | Steam turbine blades, waste incinerator parts, heat exchangers |
| Sporting goods | Golf clubs, bicycle frames, tennis rackets, hockey sticks |
Ti-6Al-4V allows designing lighter, faster and more durable components and equipment.
Ti-6Al-4V Specifications
Ti-6Al-4V is covered under the following specifications:
| Standard | Title |
|---|---|
| AMS 4911 | Titanium 6Al-4V alloy, annealed sheet/strip/plate |
| ASTM B348 | Titanium and titanium alloy bars and billets |
| ASTM F1472 | Wrought titanium-6aluminum-4vanadium alloy for surgical implant applications |
| ASTM F1108 | Titanium-6Aluminum-4Vanadium alloy for surgical implants |
| AMS 4928 | Investment castings, corrosion resistant steel, high strength, vacuum melted, titanium alloys |
| AMS 4965 | Titanium alloy sheet, strip and plate 6Al -4V annealed |
| MSRR 9545 | Titanium alloy, sheet, strip and plate 6Al – 4V, annealed |
These cover the alloy composition limits, mechanical properties, heat treatment, microstructure requirements, corrosion testing and other parameters.
Ti-6Al-4V Product Forms
Ti-6Al-4V is produced in the following forms, sizes, shapes and finishes:
| Product Form | Size Range |
|---|---|
| Sheet | 0.4 – 6.35 mm thickness |
| Plate | 6 – 250 mm thickness |
| Bar | Up to 650 mm diameter |
| Rod | Up to 650 mm diameter |
| Wire | 0.1 – 15 mm diameter |
| Tube | 2 – 300 mm diameter |
| Castings | Custom sizes and shapes |
| Forgings | Custom sizes and shapes |
Finishes include hot rolled, cold rolled, annealed, polished, machined, pickled, descaled and more.
Ti-6Al-4V Grades
Ti-6Al-4V is covered under the following ASTM grades that differ in minimum tensile and yield strength levels:
| ASTM Grade | Tensile Strength (min) MPa | Yield Strength (min) MPa |
|---|---|---|
| Grade 5 | 895 | 825 |
| Grade 23 | 965 | 895 |
| Grade 24 | 1170 | 1103 |
Grade 5 Ti-6Al-4V provides the standard properties, while Grades 23 and 24 are high-strength variants.
Ti-6Al-4V Suppliers
Ti-6Al-4V is readily available from the following major titanium suppliers and distributors:
- ATI
- VSMPO-AVISMA
- Western Metal Materials
- Baoji Titanium Industry Co.
- Western Superconducting Technologies
- Titanium Industries
Global titanium sponge production capacity was estimated around 330,000 tons in 2020, with much of this used for Ti-6Al-4V manufacturing.
Ti-6Al-4V Pricing
As of 2023, Ti-6Al-4V pricing is approximately:
| Product Form | Price Range per kg |
|---|---|
| Sheet/Plate | $15 – $50 |
| Bar/Rod | $15 – $35 |
| Wire | $25 – $60 |
| Tube | $20 – $45 |
| Castings | $25 – $100 |
| Forgings | $25 – $100 |
Prices vary based on size, thickness, grade, quantity ordered, processing, lead times and supply-demand dynamics. Mills generally offer volume-based discounts.
Ti-6Al-4V Machining
Ti-6Al-4V has low thermal conductivity so heat dissipates slowly during machining. Recommended techniques include:
- Use rigid setups to minimize vibration
- Employ high cutting speeds with slow feeds/depths
- Use high positive rake tools with sharp cutting edges
- Apply heavy flood cooling using emulsions
- Control chip formation to avoid work hardening
Carbide, cermet, CBN and diamond tools are commonly used. Coolants containing sulfur should be avoided.
Ti-6Al-4V Welding
Ti-6Al-4V can be welded using GTAW, PAW, LBW and other methods. Precautions include:
- Maintain inert gas shielding to prevent oxidation
- Limit heat input to avoid cracks and loss of strength
- Post weld heat treatment may be required
- Match composition of filler metal to base metal
Common filler metals include ER5356 and ER2319.
Ti-6Al-4V Heat Treatment
Ti-6Al-4V can be heat treated to modify its microstructure and mechanical properties:
| Process | Typical Heat Treatment |
|---|---|
| Annealing | 705°C for 2 hours, air cool |
| Stress relieving | 480 – 650°C for 2 – 4 hours, air cool |
| Solution treatment | 930 – 955°C for 1 hour, water quench |
| Aging | 480 – 595°C for 2 – 8 hours, air cool |
Annealing improves ductility and machinability. Aging increases strength. Proper heat treatment is critical for optimizing properties.
Ti-6Al-4V Forging
Forging makes solid Ti-6Al-4V components with excellent fatigue strength. Key forging aspects:
- Heat slowly to forging temperature 700 – 850°C
- Multiple forgings with intermediate anneals may be required
- Hot trim forgings before annealing
- Anneal after forging to relieve stresses
- Machine allowance should be 1 – 2 mm
Closed die forging under hammers or presses produces the best properties. Titanium requires heavy forces for forging.
Ti-6Al-4V Casting
Investment casting of Ti-6Al-4V allows making complex shapes with good surface finishes:
- Use multiple gates and risering for sound castings
- Maintain inert atmosphere during melting and casting
- Hot isostatic pressing (HIP) helps eliminate internal defects
- Chemically mill surface to remove alpha case
- Anneal castings to improve ductility
Cast Ti-6Al-4V has lower fatigue strength than wrought products.
Ti-6Al-4V Joining
Common Ti-6Al-4V joining methods include:
- Fusion welding (GTAW, PAW, LBW, electron beam)
- Brazing using Ti-Cu-Ni filler metals
- Mechanical fastening, bolts, rivets
- Adhesive bonding using epoxy or polyimide
Joint strength depends on process used. Matching alloy composition and minimizing contamination are key.
Ti-6Al-4V Handling
Recommended handling practices for Ti-6Al-4V:
- Use clean gloves to prevent contamination from skin oils and salts
- Avoid contact with hazardous metals like cadmium, mercury, gallium
- Prevent exposure to acids, chlorides and other corrosive chemicals
- Store in cool, dry, inert environments away from moisture
- Protect from scratches, nicks, dents during transport and storage
Titanium dust is highly flammable and sensitive to static discharge. Follow proper grounding, ventilation and cleaning procedures.
Ti-6Al-4V Safety
Key safety measures for handling titanium alloys:
- Wear appropriate PPE – eye protection, dust mask, gloves
- Use sufficient local exhaust ventilation when machining
- Avoid breathing fumes from welding or thermal cutting
- Prevent accumulation of chips and dust
- Ensure adequate fire extinguishing equipment is available
- Follow safe practices for compressed gas cylinders and cryogens
Titanium itself has low toxicity but processing can generate hazardous particulates.
Ti-6Al-4V Inspection
Ti-6Al-4V parts are typically inspected using:
- Visual and macro examination for defects
- Liquid penetrant testing to detect surface flaws
- Ultrasonic inspection for internal integrity
- Radiographic testing using X-ray or gamma ray
- Eddy current methods to identify cracks and voids
- Proof testing and pressure testing finished components
Grain structure, alpha case depth, surface finish and dimensions are also commonly checked.
Ti-6Al-4V Quality Assurance
Ti-6Al-4V suppliers should have quality systems certified to:
- ISO 9001 Quality Management
- AS9100 Aerospace standard
- ISO 13485 Medical devices standard
- NADCAP Special processes like heat treatment and NDT
Airframe and medical applications have additional regulatory requirements.
Advantages of Ti-6Al-4V
- Excellent strength-to-weight ratio
- Withstands extreme temperatures
- Resists corrosion in many environments
- Bio-compatible for implants
- Can be heat treated to tailor properties
- Readily formed and machined
- Available from many qualified suppliers
Limitations of Ti-6Al-4V
- More expensive than steels and aluminum alloys
- Lower stiffness than steel
- Not heat treatable to full hardness
- Subject to galling and seizing during machining
- Section sizes are limited by forging and casting capabilities
- Melting requires controlled inert atmosphere
Ti-6Al-4V vs. Other Titanium Alloys
How does Ti-6Al-4V compare to other popular titanium alloys?
| Alloy | Strength | Corrosion Resistance | Cost | Use Cases |
|---|---|---|---|---|
| Ti-6Al-4V | High | Excellent | Moderate | Aerospace, marine, biomedical |
| CP Titanium | Medium | Excellent | Low | Chemical, seawater systems |
| Ti-10V-2Fe-3Al | Very High | Good | High | Aerospace fasteners, rigging |
| Ti-3Al-2.5V | Medium | Excellent | Moderate | Jet engines, airframes |
| Ti-13V-11Cr-3Al | High | Excellent | Very High | Aerospace components |
Ti-6Al-4V provides the best all-round properties at a reasonable cost. Other alloys offer higher strength or corrosion performance for specialized applications.
FAQ
Q: What is Ti-6Al-4V used for?
A: Ti-6Al-4V is widely used in aerospace, marine, chemical processing, biomedical, and consumer applications where high strength, low weight, and corrosion resistance are needed.
Q: Is Ti-6Al-4V stronger than steel?
A: Yes, Ti-6Al-4V has a higher strength-to-weight ratio than most steels, but lower stiffness. It is about 60% heavier than aluminum.
Q: Is Ti-6Al-4V compatible for medical implants?
A: Yes, Ti-6Al-4V has excellent biocompatibility and commonly used for joint replacements, dental implants, pacemakers, and fracture fixation devices.
Q: Does Ti-6Al-4V require heat treatment?
A: Ti-6Al-4V can be heat treated to modify its properties. Solution treatment and aging can significantly increase its strength.
Q: What is the difference between Grade 5 and Grade 23 Ti-6Al-4V?
A: Grade 5 is the standard alloy with 895 MPa minimum tensile strength. Grade 23 has higher strength requirements of 965 MPa minimum.
Q: What is the corrosion resistance of Ti-6Al-4V?
A: Ti-6Al-4V has excellent corrosion resistance to most acids, chlorides, and saltwater environments. Its passivity is maintained across a wide pH range.
Q: Can you weld Ti-6Al-4V?
A: Yes, welding methods like GTAW, LBW, and PAW can be used to weld Ti-6Al-4V. Proper procedures should be followed to ensure joint integrity.
Q: What is the cost of Ti-6Al-4V compared to other metals?
A: On a per pound basis, Ti-6Al-4V is more expensive than steels and aluminum alloys, but cheaper than exotic alloys like Inconel or Hastelloy.
Q: What are some alternatives to Ti-6Al-4V?
A: For aerospace use, Ti-10V-2Fe-3Al provides higher strength. For corrosion resistance, CP Titanium or Ti-3Al-2.5V are excellent. Ti-1023 and Ti-5553 are newer high-strength alloys.