TC4 is the Chinese designation for the most widely used titanium alloy, corresponding to Ti-6Al-4V (6 percent aluminum, 4 percent vanadium) under standards such as ASTM Grade 5. It is an alpha-beta alloy, meaning it contains a mixture of hexagonal close-packed (alpha) and body-centered cubic (beta) phases. This two-phase structure gives TC4 an excellent balance of high strength, low density, good corrosion resistance, and favorable high-temperature performance.

The nominal chemical composition of TC4 is: aluminum 5.5 to 6.8 percent, vanadium 3.5 to 4.5 percent, iron up to 0.30 percent, oxygen up to 0.20 percent, carbon up to 0.08 percent, nitrogen up to 0.05 percent, hydrogen up to 0.015 percent, and the balance titanium. The addition of aluminum stabilizes the alpha phase and increases strength, while vanadium stabilizes the beta phase and improves ductility and hardenability.

Key mechanical properties (typical values for annealed condition):

● Tensile strength: 895 to 1,000 MPa (minimum 895 MPa)

● Yield strength (0.2% offset): 825 to 900 MPa

● Elongation: 10 to 15 percent

● Reduction of area: 20 to 25 percent

● Density: 4.43 g/cm³ (about 56 percent that of steel)

● Melting point: approximately 1,600 to 1,650°C

● Modulus of elasticity: 110 to 114 GPa (about half that of steel)

● Hardness: 30 to 36 HRC (annealed); can be heat treated to higher hardness

TC4 offers outstanding corrosion resistance in seawater, brine, oxidizing acids (nitric, chromic), and many organic environments. It is resistant to stress corrosion cracking and has excellent biocompatibility, making it suitable for medical implants. The alloy maintains useful strength up to about 400°C and can be used briefly at higher temperatures. It is heat treatable: solution treatment and aging (STA) can increase tensile strength to over 1,100 MPa. TC4 is weldable (by GTAW, plasma, electron beam) but requires shielding gas to prevent contamination. Its machinability is poor compared to steel, requiring sharp tools, low speeds, and high coolant flow.

Common international equivalents:

● ASTM B348 Grade 5 (USA)

● Ti-6Al-4V (ISO 5832-3 for surgical implants)

● IMI 318 (UK)

● BT6 (Russian)

● TAV (European)

Typical applications of TC4 include:

● Aerospace: aircraft engine fan blades, compressor discs, airframes, fasteners, landing gear components, and structural parts.

● Medical: surgical implants such as hip and knee joints, bone plates, screws, and dental implants.

● Marine: propeller shafts, heat exchangers, valve bodies, and deep-sea pressure housings.

● Chemical processing: reactor vessels, piping systems, and pump components in corrosive environments.

● Automotive: high-performance engine valves and connecting rods.

● Sporting goods: golf club heads, bicycle frames, and tennis rackets.

TC4 is also available in various product forms: bar, sheet, plate, tube, wire, forging billet, and powder for additive manufacturing (3D printing). The alloy can be supplied in annealed, solution treated and aged (STA), or beta-annealed conditions. For medical applications, a special grade called TC4 ELI (Extra Low Interstitial) with lower oxygen, nitrogen, and iron content offers improved fracture toughness and ductility.

Selection guidance: TC4 is the default choice for high-strength, lightweight, corrosion-resistant applications across aerospace, medical, and marine industries. For applications requiring maximum ductility and formability, commercially pure titanium (TA1-TA4) may be preferred. For even higher strength (over 1,200 MPa), other alloys like TB6 (Ti-10V-2Fe-3Al) or TC18 (Ti-5Al-5Mo-5V-1Cr-1Fe) are available. TC4 remains the most versatile and widely produced titanium alloy globally.