What is the TC4Ti-6Al-4V titanium alloy?

TC4 (Ti-6Al-4V) is the most widely used and technically mature α+β duplex titanium alloy in the world. Often referred to as the “king of titanium alloys,” it accounts for more than 50% of global titanium alloy consumption. With its core advantages of low density, high specific strength, excellent corrosion resistance, and good biocompatibility, it is widely used in high-end sectors such as aerospace, medical, defense, and chemical engineering.

Basic Information

National Standard Designation: TC4 (GB/T 3620.1)

International Equivalent: Ti-6Al-4V (ASTM Grade 5)

Alloy Type: α+β-phase duplex titanium alloy (heat-treatable)

Development Background: Developed in the United States in 1954, marking a milestone in the industrialization of titanium alloys

Chemical Composition (Mass Fraction, %)

Function: Al (α-stabilizer) enhances strength and heat resistance; V (β-stabilizer) improves ductility and hardenability.

Key Properties (Annealed State, Room Temperature)

1. Physical Properties

Density: 4.43–4.51 g/cm³ (approximately 60% that of steel)

Modulus of elasticity: ~110 GPa (approximately half that of steel)

Coefficient of thermal expansion: 8.6–9.4 × 10⁻⁶/°C (20–100°C)

Thermal conductivity: ~6.7 W/(m·K) (20°C)

Operating temperature: –196°C to 550°C (long-term ≤ 400°C)

2. Mechanical Properties (National Standard GB/T 2965)

Tensile Strength (σb): ≥895 MPa (up to 1100 MPa after heat treatment)

Yield Strength (σ₀.₂): ≥825 MPa

Elongation (δ₅): ≥10%

Reduction of Area (ψ): ≥25%

Hardness: HB 300–340 (annealed); HV 330–380 (solution treated and aged)

Specific strength: ~23.5 (far exceeds that of alloy steel and is approximately twice that of 304 stainless steel)

3. Key Properties

Corrosion Resistance: Exhibits excellent performance in seawater, chloride solutions, and organic acids, outperforming stainless steel.

Biocompatibility: Non-toxic and non-allergenic, making it the material of choice for medical implants.

Weldability: Can be welded using TIG welding, electron beam welding, and other methods; weld joint strength can reach over 90% of the base material’s strength.

Fatigue Resistance: Fatigue limit of 500–650 MPa, superior to most structural steels.

Microstructure

At room temperature, the microstructure consists of an α+β two-phase system: the α phase (hexagonal close-packed) provides high-temperature strength and stability, while the β phase (body-centered cubic) enhances toughness and workability.

The microstructure can be controlled through solution treatment and aging heat treatment to achieve a balance between strength and ductility.

Typical Application Areas

1. Aerospace (Largest market share, accounting for over 80%): Engine blades/disks, airframe structures, landing gear, rocket casings.
2. Medical: Artificial joints, bone screws, dental implants, surgical instruments (ELI-grade ultra-low-clearance versions).
3. Defense: Armor, submarine pressure hulls, missile structural components.
4. Marine Engineering: Seawater piping, pumps and valves, deep-sea equipment.
5. Chemical Industry: Corrosion-resistant vessels, heat exchangers, nuclear power components.
6. High-End Consumer Products: High-end bicycles, sports equipment, casings for 3C products.

Summary of Advantages and Disadvantages

Advantages: Extremely high specific strength, good corrosion resistance, biocompatibility, heat treatability, stability at moderate temperatures, and good weldability.

Disadvantages: Low elastic modulus (prone to springback), poor machinability, higher cost than steel or aluminum, and reduced strength at high temperatures (>550°C).

Standards and Grades

National Standards: GB/T 2965, GB/T 3620.1, GJB 2218A (Aviation).

International Standards: ASTM B348, AMS 4928.

Special Grades: ELI Grade (Extra-Low-Impurity, O ≤ 0.13%), used in medical and high-toughness applications.