Differences and Applications of TB (β-type Titanium Alloy) and TC (α+β-type Titanium Alloy)

According to the national standard GB/T-3620.1: TB = β-type/near-β-type titanium alloy; TC = α+β dual-phase titanium alloy. The core differences between the two lie in their metallographic structure, mechanical properties, processing characteristics, heat resistance limit, cost, and applicable scenarios.

I. Basic Differences Comparison

1. Metallographic Structure and Alloying Elements

• TB Series (β-Titanium Alloys, TB2, TB3, TB5, TB6, TB8): Contains a large amount of β-stabilizing elements: vanadium (V), molybdenum (Mo), chromium (Cr); predominantly body-centered cubic β phase at room temperature; metastable β structure is obtained after solution treatment, and fine α phase precipitates after aging for strengthening.

• TC Series (α+β Titanium Alloys, TC4, TC11, TC15, TC21)
Contains both α-stabilizing element aluminum (Al) and β-stabilizing element vanadium (V); composed of a mixture of close-packed hexagonal α phase and body-centered cubic β phase, the ratio of which can be adjusted through heat treatment.

2. Mechanical Properties

TB Series

1. Solution-annealed state: Excellent plasticity, suitable for cold stamping, cold heading, and bending; cold forming performance far superior to TC.

2. After solution treatment and aging strengthening, tensile strength can reach 1300–1650 MPa, with a higher upper limit.

3. Lower elastic modulus, greater springback; excellent hardenability, suitable for large-section forgings (thickness > 150 mm still provides overall strengthening).

4. Disadvantages: Poor thermal stability, long-term service temperature ≤ 300℃; poor machinability; slightly higher density; higher cost.

TC Series (represented by TC4)

1. Annealed tensile strength: approximately 895–930 MPa; after heat treatment, maximum strength approximately 1100 MPa, ultimate strength lower than TB;

2. Moderate plasticity, mainly relying on hot forging and hot forming, difficult to cold work;

3. Better heat resistance, TC4 can operate continuously at 400℃, TC11 up to 500℃;

4. Better machinability and weldability than TB, mature technology, lower price, high cost-performance ratio.

3. Corrosion Resistance

• TB: Excellent resistance to seawater and chloride ion corrosion; better resistance to dissimilar metal contact corrosion, less prone to galvanic corrosion when in contact with stainless steel; some grades (TB8) have outstanding resistance to strong acids and high-temperature oxidation.

• TC: Good corrosion resistance, sufficient for seawater and weak acid environments; but slightly weaker than TB in highly corrosive conditions.

4. Processing and Cost

• TB: Complex smelting, forging, and heat treatment processes, requiring strict heat treatment control; excellent cold working, suitable for complex thin-walled parts; price 40%-100% higher than TC4.

• TC: Mature hot working process, good welding performance, low mass production cost; accounts for approximately 80% of global titanium alloy usage.

II. Commonly Used Grades and Application Scenarios

TB Series (β-Titanium Alloy) Applications

1. TB2, TB3: Extremely strong cold forming performance; used for high-strength bolts in aerospace, elastic springs, corrugated pipe fittings, fasteners, satellite connectors; suitable for cold-headed bolts and titanium springs.

2. TB5 (Ti-15V-3Cr-3Al-3Sn): Strongest sheet metal cold stamping capability; aircraft skin, honeycomb structures, thin-walled irregular parts, lightweight structural parts for motorcycles.

3. TB6 (Ti-10V-2Fe-3Al, near-β alloy): The most mainstream high-strength titanium alloy; used in aircraft landing gear, wing joints, large load-bearing forgings, racing linkages, and high-strength bolts for high-end motorcycles; can be isothermally forged, resulting in significant weight reduction.

4. TB8 (β-21S): Strong oxidation resistance; used in engine exhaust components, special chemical equipment, and high-temperature conduits.

TC Series (α+β Titanium Alloy) Applications

1. TC4 (Ti-6Al-4V, Grade 5): The most versatile; used in aerospace structural components, engine fans, orthopedic implants (TC4-ELI medical grade), bicycle frames, ordinary titanium bolts, seawater equipment, and pressure vessels; the first choice for long-term operation below 400℃.

2. TC11: Heat-resistant; used in aero-engine compressor discs and blades, capable of long-term operation at 500℃.

3. TC15, TC21: High strength and toughness; used in aircraft load-bearing frames, landing gear joints, and military structural components.

TB (β titanium alloy): Primarily characterized by ultra-high strength and excellent cold working; poor heat resistance, expensive; used in high-strength elastic components, large forgings, and high-end fasteners.

• TC (α+β titanium alloy): Balanced overall performance, better heat resistance, easy to weld and process, high cost-effectiveness, and the most versatile.