Grade 5 (Ti-6Al-4V) titanium alloy is one of the earliest developed and most widely used titanium alloys in the world. It accounts for more than half of the total global production of titanium alloy semi-finished products, with over 80% of its applications in the aerospace industry. This alloy primarily consists of 6% aluminum (Al) and 4% vanadium (V), achieving a well-balanced combination of strength, corrosion resistance, weldability, high-temperature resistance, and weight. Aluminum strengthens the α-phase through solid solution strengthening, enhancing room-temperature strength and thermal strength, while vanadium improves both strength and ductility. Additionally, vanadium suppresses the formation of the α2 superstructure phase, preventing embrittlement during prolonged use.
The primary characteristics of Grade 5 titanium alloy are its excellent overall performance and good processing properties. It also has superior superplasticity, making it suitable for various pressure forming methods and welding techniques. Grade 5 titanium alloy is available in the form of bars, forgings, thin sheets, thick plates, profiles, and wires. It is mainly used in the annealed condition but can also undergo solution treatment and aging for strengthening. However, its hardenability is limited to sections no thicker than 25–30mm, making solution-aging treatment unsuitable for large components. Currently, various modified versions of Ti-6Al-4V titanium alloy have been developed in different countries to meet specific operating conditions and process requirements. These modifications primarily differ in Al and V content, lower interstitial impurity levels, or the addition of trace elements such as Re.
In the aerospace sector, Grade 5 titanium alloy is widely used for manufacturing structural components in aircraft, including beams, bulkheads, slides, landing gear beams, as well as fan and compressor discs and blades in aircraft engines. It is also used in spacecraft structures, pressure vessels, and various types of fasteners. When replacing 30CrMnSiA structural steel with Grade 5 titanium alloy, the weight of components can be reduced by approximately 30%.
Grade 5 titanium alloy has also found extensive applications in civilian industries, such as gas turbine blades in power generation, ship propellers in the marine industry, offshore drilling platforms in ocean engineering, corrosion-resistant pumps in chemical industries, medical implants, and sports equipment.
Additionally, Grade 5 titanium alloy is suitable for manufacturing automotive frames, crankshafts, connecting rods, bolts, intake valves, and suspension springs. Equivalent designations include:
• USA: Ti-6Al-4V, Ti-6Al-4V ELI, Ti-6Al-4V SP, Ti-6Al-4V ELI SP
Note: After heat treatment, such as quenching + aging (STA), the strength can be further increased to 1100–1200 MPa.
Heat Treatment Processes
Ti-6Al-4V can undergo various heat treatment processes to optimize its properties:
• Annealing: Reduces residual stress and improves ductility.
• Temperature: 705–785°C, held for 1–2 hours, air-cooled or furnace-cooled.
• Solution Treatment & Aging (STA):
• Solution Treatment: 900–950°C, held for 1 hour, water-cooled or air-cooled.
• Aging Treatment: 500–600°C, held for 4–8 hours, air-cooled.
• Purpose: Enhances strength and fatigue resistance.
Machinability
Due to its high strength, low thermal conductivity, and low elastic modulus, Ti-6Al-4V is challenging to machine, leading to tool wear and work hardening. To ensure efficient machining:
• Use low speeds, high feed rates, and sharp carbide tools.
• Apply coolants (emulsified fluids or cutting oils) to reduce cutting heat.
• Use high feed rates to avoid work hardening.
Weldability
• Ti-6Al-4V has good weldability and is commonly welded using Tungsten Inert Gas (TIG) welding, Electron Beam Welding (EBW), and Laser Beam Welding (LBW).
• Since titanium readily reacts with oxygen, nitrogen, and hydrogen in the air, high-purity argon shielding is required during welding to prevent embrittlement.
• Suspension components for sports cars, exhaust systems
Marine Engineering:
• Submarine hulls, deep-sea exploration equipment
• Ship propulsion systems
Energy Industry:
• Chemical processing equipment (heat exchangers, reactors)
• Components for oil drilling platforms
Advantages & Disadvantages of Ti-6Al-4V
Advantages:
✔ High strength-to-weight ratio (twice that of steel)
✔ Excellent corrosion resistance, suitable for harsh environments
✔ Good weldability
✔ Biocompatibility, ideal for medical applications
✔ Can be further optimized through heat treatment
Disadvantages:
✘ Difficult to machine, leading to rapid tool wear
✘ High cost
✘ Low thermal conductivity, causing high cutting temperatures
✘ Low elastic modulus, prone to springback
Product Forms
Available in the following forms: bars, plates, tubes, wires, strips, forgings, castings, and machined components. Surface treatments and heat treatments can be customized based on specific requirements.
Pricing & Production Standards
Pricing depends on demand, material specifications, quantity, and delivery time. Production can follow ASTM B381 (USA) standards or GB/T3620.1 (China) standards, with other standards available upon request.
