Grade 5 Titanium Alloy

Introduction:

Grade 5 alloy is the most widely used titanium alloy in the world. It exhibits an α+β dual-phase structure at room temperature, hence named α+β titanium alloy. It has excellent comprehensive mechanical properties, can be heat treated for strengthening, and possesses good forgeability, stamping, and welding properties. It also exhibits high strength at room temperature, good heat resistance up to 150~500°C, excellent low-temperature toughness, and resistance to seawater corrosion and hot salt stress corrosion. Additionally, Grade 5 titanium alloy has characteristics such as low density, high specific strength, low elastic modulus, low thermal conductivity, non-magnetism, and non-toxicity.

Chemical Composition:

- Aluminum (Al): 5.50~6.75%

- Vanadium (V): 3.50~4.50%

- Carbon (C): <0.08%

- Nitrogen (N): ≤0.05%

- Hydrogen (H): ≤0.015%

- Iron (Fe): ≤0.40%

- Oxygen (O): ≤0.20%

- Titanium (Ti): Balance

Mechanical Properties:

- Density (ρ): Approximately 442 kg/m3

- Tensile Strength (σb): ≥895 MPa

- Specified Residual Elongation Stress (σor0.2): ≥830 MPa

- Elongation (δ): ≥10%

- Reduction of Area (ψ): ≥25%

- Brinell Hardness (HBS10/1500) (Annealed Condition): ≤350

Applications:

Grade 5 titanium alloy is widely used in stamping parts, welded parts, forged parts, and various components for bending processing operating below 400°C. It can also be used as a low-temperature structural material for parts operating below 400°C for extended periods. Additionally, it finds applications in structural forgings, various containers, pumps, low-temperature components, ship pressure hulls, tank tracks, aircraft engine compressor blades, rocket engine casings, components of liquid hydrogen fuel tanks for rockets and missiles, heaters for petroleum refining and seawater desalination, and environmental pollution control devices, among others.

Heat Treatment Process:

1. Stress Relief Annealing: The purpose is to eliminate or reduce residual stresses generated during processing to prevent chemical corrosion in some corrosive environments and reduce deformation.

2. Full Annealing: The purpose is to obtain good toughness, improve processability, facilitate further processing, and improve dimensional and structural stability.

3. Solution Treatment and Aging: The purpose is to further strengthen the alloy through solution treatment and aging for α+β titanium alloys.

Precautions for Cutting:

1. Due to the small elastic modulus of titanium alloys, excessive clamping deformation and stress deformation of workpieces during processing can reduce machining accuracy. Clamping force during workpiece installation should not be too high, and auxiliary support can be added if necessary.

2. The use of cutting fluids containing hydrogen may cause hydrogen embrittlement due to the release of hydrogen gas at high temperatures during cutting, leading to hydrogen-induced cracking of titanium alloys.

3. Chlorides in cutting fluids may decompose or volatilize toxic gases during use. Safety precautions should be taken during use, and parts should be thoroughly cleaned with chlorine-free cleaning agents after cutting to remove residual chlorides.

4. Contact between fixtures made of lead or zinc-based alloys and titanium alloys should be avoided, and the use of copper, tin, cadmium, and their alloys should also be prohibited.

5. All fixtures or other devices in contact with titanium alloys must be clean. Cleaned titanium alloy parts should be protected from grease or fingerprint contamination to prevent stress corrosion of salts (sodium chloride) in the future.

6. Generally, there is no fire hazard during cutting of titanium alloys. Only when micro-cutting, the fine chips produced may ignite and burn. To prevent fires, apart from pouring a large amount of cutting fluid, accumulation of chips on the machine tool should be prevented, and blunt tools should be replaced immediately or cutting speed should be reduced and feed rate increased to increase chip thickness. In case of fire, talcum powder, limestone powder, dry sand, and other extinguishing agents should be used, and carbon tetrachloride and carbon dioxide fire extinguishers should be strictly prohibited. Water should not be used because it can accelerate combustion and even cause hydrogen explosions.