Ti-6Al-4V (Gr5, TC4)

1. Exceptional specific strength:
With a density of only 4.43 g/cm³, it exhibits tensile strength ≥ 895 MPa in annealed condition (≥ 1100 MPa in STA condition), delivering significant lightweighting effects and serving as a core material in aerospace and racing applications.
2. Superior corrosion resistance:
3. Its corrosion resistance far exceeds that of stainless steel in seawater, chlorides, and most acidic and alkaline media, eliminating the need for coating protection and making it suitable for marine and chemical environments.
3. Good biocompatibility:
Non-toxic, non-allergenic, and with excellent osseointegration properties, it is one of the preferred materials for global implantable medical devices, complying with the ASTM F136 standard.
4. Excellent performance at moderate temperatures:
It can operate stably for long periods at ≤ 400°C and withstand short-term exposure to above 500°C while maintaining structural and property stability.
5. Superior fatigue performance:
A high-cycle fatigue limit of 500-700 MPa and strong resistance to fatigue crack propagation make it ideal for dynamic load conditions.
6. Mature standard system:
Conforms to multiple international standards including ASTM B348, ASTM F136 (medical), ISO 5832-3, AMS 4928, and GB/T 2965, supported by a mature global supply chain.

The heat treatment of Ti-6Al-4V is mainly used to adjust the match between strength and ductility, with common specifications as follows:
1. Annealing (for optimal ductility and dimensional stability, the most commonly used condition):
Normal Annealing:
Heat to 700-800°C, hold for 1-2 hours, then air cool. This results in an equiaxed α+β microstructure with good overall properties.
Double Annealing:
First stage at 850-950°C, air cool; second stage at 700-750°C, air cool. Used to improve fatigue performance and fracture toughness.
2. Solution Treatment and Aging (STA, for achieving maximum strength):
Solution Treatment:
Heat to 925-955°C, hold for 0.5-1 hour, then water quench or oil quench (to obtain a metastable β phase).
Aging Treatment:
Heat to 480-595°C, hold for 4-8 hours, then air cool. Fine α phase precipitates, significantly increasing strength (tensile strength ≥ 1100 MPa).
Note: Heat treatment should be performed under vacuum or inert gas protection to avoid surface oxidation and contamination ('α embrittlement layer'). Quenching speed must be sufficiently fast to retain the β phase, but thin sections may use air cooling.

Long-term continuous operating temperature (primarily based on strength and oxidation resistance):
It is recommended to be ≤ 400°C. At this temperature, the microstructure remains stable, creep rate is controllable, and performance degradation is acceptable.
Short-term exposure temperature:
Can reach as high as 500-550°C (e.g., short-term overheating in aircraft engines), but strength and oxidation resistance will significantly decrease.
Maximum design temperature for pressure-bearing structural components:
Typically considered as 350-400°C, and creep and long-term strength calculations need to be performed based on specific stress levels.
Low-temperature properties:
Ti-6Al-4V exhibits increased strength and acceptable ductility at low temperatures (down to -196°C), but it is not as good as near-α alloys such as TA7. It is generally not the first choice for deep cryogenic engineering applications.

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Selection Recommendations: If you require the highest strength-to-weight ratio, moderate temperature resistance, and good overall performance, choose Ti-6Al-4V (Grade 5).
If you prioritize ultimate corrosion resistance, formability, and cost control, and have lower strength requirements, pure titanium (Grade 2) is a more economical choice.

Ti-6Al-4V has good welding properties, but strict adherence to titanium alloy welding process specifications is required:

1. Recommended Welding Methods: TIG (Tungsten Inert Gas Welding), MIG (Metal Inert Gas Welding), Plasma Welding, Electron Beam Welding, Laser Welding, and Friction Welding.
2. Pre-Welding Preparation: The welding area must be strictly cleaned to remove oil, scale, and moisture. Mechanical cleaning or chemical cleaning (pickling) is recommended.
3. Protective Gas: High-purity argon gas (≥ 99.99%) should be used for welding and backside protection to prevent high-temperature oxidation and contamination by hydrogen, oxygen, and nitrogen. For critical applications, an argon gas trailing shield can be employed.
4. Post-Weld Heat Treatment: Post-weld stress-relief annealing (approximately 500-650°C, air-cooled) is recommended to eliminate residual stresses and restore weld ductility. Post-weld heat treatment is particularly important for thick sections or highly constrained structures.
5. Filler Metal: Ti-6Al-4V filler wire of the same material (e.g., AWS A5.16 ERTi-5) is recommended to ensure weld composition and performance match.
6. Key Control Points: Strict control of heat input (linear energy) is required to avoid excessive heat input leading to weld microstructure coarsening and reduced ductility.

Applicable for alternative scenarios (Ti-6Al-4V, as a general-purpose titanium alloy, is the benchmark choice for the majority of applications):
When strength, corrosion resistance, workability, and cost need to be balanced, Ti-6Al-4V is the preferred choice, capable of replacing most industrial pure titanium and low-alloy titanium materials.
In non-extreme high-temperature conditions (≤ 400°C), it can replace near-α alloys such as TA7, but its welding performance and low-temperature properties are inferior to those of TA7.
For non-extreme high-strength requirements (≤ 1200 MPa), it can replace higher-strength β-titanium alloys (e.g., Ti-10V-2Fe-3Al) with lower cost and better workability.

Scenarios where substitution is not suitable (other brands should be selected):
For long-term service at extreme high temperatures (> 450°C): High-temperature titanium alloys (e.g., Ti-6242S, IMI 834) should be selected.
For extremely low temperatures (< -100°C) with very high plasticity requirements: TA7 is preferable.
For biomedical applications requiring an extremely low modulus of elasticity: Beta titanium alloys (e.g., Ti-12Mo-6Zr-2Fe, TMZF) can be considered.
For ultra-high strength requirements (> 1300 MPa): Beta or metastable beta titanium alloys (e.g., Ti-15V-3Cr-3Al-3Sn) are needed.

Material Selection Recommendations: Please provide detailed operating conditions (temperature range, load type, medium environment, welding requirements, service life) for specific material selection. We can assist with technical and economic comparative analysis to help you make the optimal choice between Ti-6Al-4V and other titanium alloy grades.