Ti Grade 2 is commercially pure titanium. Ti Grade 5 is the most widely used titanium alloy in the world — Ti6Al4V. The difference between them is the strength gained from the aluminium and vanadium additions.
Aluminium and vanadium
There are no alloying elements in the composition of Grade 2; apart from titanium it contains only limited impurities (iron, oxygen, nitrogen, carbon). Grade 5 contains 5.50–6.75% aluminium and 3.50–4.50% vanadium.
Aluminium stabilises the alpha phase and vanadium the beta phase; the result is a two-phase (alpha + beta) structure that can be hardened by heat treatment. The figures on our datasheets show the difference clearly: the yield strength of Grade 2 is ≥275 MPa against ≥830 MPa for Grade 5 — three times as much. Tensile strength rises from 345 MPa to 895 MPa.
The price is ductility and formability. The elongation of Grade 2 is ≥20% against ≥10% for Grade 5. Grade 2 can be cold formed and welds very easily; Grade 5 requires hot forming and controlled welding.
In corrosion resistance both are excellent — pure titanium is somewhat superior in that respect. In other words the reason for choosing Grade 5 is never corrosion, always strength.
Comparison in numbers
| PROPERTY | Ti Grade 2 | Ti Grade 5 (Ti6Al4V) |
|---|---|---|
| Aluminium (Al) | — | 5.50 – 6.75% |
| Vanadium (V) | — | 3.50 – 4.50% |
| Iron (Fe) | ≤ 0.30% | ≤ 0.20% |
| Oxygen (O) | ≤ 0.25% | ≤ 0.20% |
| Nitrogen (N) | ≤ 0.03% | ≤ 0.05% |
| Carbon (C) | ≤ 0.08% | ≤ 0.08% |
| Tensile strength Rm | ≥ 345 N/mm² | ≥ 895 N/mm² |
| Yield strength Rp0.2 | ≥ 275 N/mm² | ≥ 830 N/mm² |
| Elongation | ≥ 20% | ≥ 10% |
| Hardness | ≤ 150 HB | ≥ 310 HB |
| Density | 4.51 g/cm³ | ≥ 4.43 g/cm³ |
| Modulus of elasticity | 105 kN/mm² | 114 kN/mm² |
| Thermal conductivity | 20 W/m·K | ≥ 7.1 W/m·K |
| UNS | R50400 | R56400 |
| AMS | 4902 · 4941 · 4942 · 4951 | 4928 (bar, forging) · 4911 (plate, sheet) |
Values are taken from our product datasheets; section thickness and the applied heat treatment regime change the result.
Which one, and when?
Ti Grade 2 is sufficient — chemical plant piping and heat exchangers, seawater systems, desalination plants, anode and electrode structures, medical implant bodies, architectural cladding. Anywhere corrosion resistance is enough and strength is secondary.
Ti Grade 5 is required — aircraft structural members, engine components, landing gear parts, hip and knee prostheses, racing car parts, high-performance fasteners. If the specification calls out AMS 4928 or AMS 4911, Grade 2 is not an acceptable substitute.
Neighbouring grades
For softer and harder versions of pure titanium there are Ti Grade 1 and Ti Grade 4. For medical applications, the extra low interstitial version of Grade 5 is Ti Grade 5 ELI.
Technical datasheets
Ti Grade 2 — 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.