Ti Grade 4 is the strongest grade of commercially pure titanium. Ti Grade 5 is the standard grade of alloyed titanium (Ti6Al4V). These are the two titanium classes that come closest to each other in strength — which is why the choice is sometimes debated.
By impurity, or by alloying?
Grade 4 takes its strength from oxygen: according to our datasheet oxygen is ≤0.40% and iron ≤0.50% — the highest limits among the pure titanium grades. It contains no alloying elements.
Grade 5 contains 5.50–6.75% aluminium and 3.50–4.50% vanadium. That moves the material into an alpha + beta structure and makes it hardenable by heat treatment — which is not possible with Grade 4.
The figures show a clear step between them: the yield strength of Grade 4 is ≥485 N/mm² and its tensile strength ≥550 N/mm². In Grade 5 those rise to ≥830 and ≥895 N/mm². Hardness rises from ≤200 HB to ≥310 HB.
The advantage of Grade 4 is on the corrosion side: being unalloyed, its corrosion resistance is somewhat better than that of Grade 5 and its weldability is higher. It is also preferred in some medical applications because it contains no aluminium or vanadium.
Comparison in numbers
| PROPERTY | Ti Grade 4 | Ti Grade 5 (Ti6Al4V) |
|---|---|---|
| Aluminium (Al) | — | 5.50 – 6.75% |
| Vanadium (V) | — | 3.50 – 4.50% |
| Oxygen (O) | ≤ 0.40% | ≤ 0.20% |
| Iron (Fe) | ≤ 0.50% | ≤ 0.20% |
| Nitrogen (N) | ≤ 0.05% | ≤ 0.05% |
| Hardenable by heat treatment | No | Yes |
| Tensile strength Rm | ≥ 550 N/mm² | ≥ 895 N/mm² |
| Yield strength Rp0.2 | ≥ 485 N/mm² | ≥ 830 N/mm² |
| Elongation | ≥ 15% | ≥ 10% |
| Hardness | ≤ 200 HB | ≥ 310 HB |
| Density | 4.51 g/cm³ | ≥ 4.43 g/cm³ |
| Modulus of elasticity | 106 kN/mm² | 114 kN/mm² |
| Thermal conductivity | 18 W/m·K | ≥ 7.1 W/m·K |
| UNS | R50700 | R56400 |
| AMS | 4901 · 4921 | 4928 · 4911 |
Values are taken from our product datasheets; section thickness and the applied heat treatment regime change the result.
Which one, and when?
Ti Grade 4 is preferred — dental implants and surgical screws, high-strength parts where corrosion comes first, welded pressure vessels, aircraft skin and piping systems. It takes the place of Grade 5 in medical and chemical applications that require an unalloyed material.
Ti Grade 5 is required — aircraft structural parts, engine components, landing gear members, highly stressed fasteners, orthopaedic implants. If the strength-to-weight ratio is critical, Grade 4 is not enough.
Neighbouring grades
For the softer pure titanium grades, see our Ti Grade 1 – Grade 2 comparison; for medical applications, our Ti Grade 5 – Grade 5 ELI article.
Technical datasheets
Ti Grade 4 — chemical composition, mechanical values, standard equivalents
Ti Grade 5 — chemical composition, mechanical values, standard equivalents
Both grades are supplied to order in round bar, flat bar, plate, sheet, pipe and forged forms. Contact us for a quotation.