1. Aluminum and Vanadium Content
The main alloying elements of Grade 5 titanium alloy are aluminum (Al) as an alpha stabilizer and vanadium (V) as a beta stabilizer. Their specified composition ranges are:
Aluminum (Al): 5.5% – 6.75% by weight
Vanadium (V): 3.5% – 4.5% by weight
Aluminum improves tensile strength, creep resistance, and elastic modulus, while vanadium enhances ductility, toughness, and forgeability. Titanium is the balance element.
2. Oxygen, Nitrogen, and Hydrogen Content Requirements
Interstitial elements such as oxygen, nitrogen, and hydrogen strongly affect mechanical properties, especially ductility and fracture toughness. Strict upper limits are specified:
Oxygen (O): ≤ 0.20% by weight
Nitrogen (N): ≤ 0.05% by weight
Hydrogen (H): ≤ 0.015% by weight
Oxygen and nitrogen increase strength and hardness but reduce ductility. Hydrogen must be tightly controlled to prevent hydrogen embrittlement, which can lead to cracking in service.
3. Maximum Iron Content
Iron is a common beta‑stabilizing impurity element in titanium alloys. For standard Grade 5 titanium alloy:
Iron (Fe): ≤ 0.40% by weight
Excessive iron can cause microstructural inhomogeneity and affect consistency in mechanical properties.
4. Low‑Oxygen / High‑Purity Grades
Yes, Grade 5 titanium alloy has well‑established low‑oxygen and high‑purity grades, most commonly referred to as Grade 5 ELI (Extra Low Interstitial).
Grade 5 ELI is designed for applications requiring extremely high toughness, fatigue resistance, and reliability, such as biomedical implants and critical aerospace components. Compared with standard Grade 5, it has much tighter controls on interstitial and impurity elements:
Oxygen (O): ≤ 0.13% (significantly lower than the standard 0.20%)
Iron (Fe): ≤ 0.25%
Nitrogen and hydrogen are also controlled to lower maximum levels
In summary, standard Grade 5 (Ti‑6Al‑4V) has defined ranges for Al, V, O, N, H, and Fe, while Grade 5 ELI provides a low‑oxygen, high‑purity option for high‑performance and high‑reliability applications.
