Titanium Grade 2 or Grade 5: you may be paying for strength you don't use
Grade 5 is the default titanium in most people’s heads. It is roughly half of all titanium used, it is what “titanium” means in aerospace, and it appears on drawings where Grade 2 would do the job for less money and less trouble.
Sometimes that substitution is wrong. Often it is not. Here is how to tell.
The two alloys
Grade 2 is commercially pure titanium — about 99 % titanium with controlled oxygen and iron. Single-phase alpha structure. Soft, ductile, extremely corrosion resistant, easy to weld and form.
Grade 5 is Ti-6Al-4V: 6 % aluminium, 4 % vanadium. Two-phase alpha-beta structure, heat treatable, roughly three times the strength of Grade 2.
| Grade 2 | Grade 5 (Ti-6Al-4V) | |
|---|---|---|
| Yield strength | ~275 MPa | ~830 MPa |
| Tensile strength | ~345 MPa | ~900 MPa |
| Hardness | ~145 HV | ~340 HV (~36 HRC) |
| Elongation | ~20 % | ~14 % |
| Max service temperature | ~300 °C | ~400 °C |
| Weldability | Excellent | Good, needs care and inert shielding |
| Formability | Good cold | Poor cold, hot forming required |
| Corrosion resistance | Best of the two | Very good, slightly below Gr 2 |
| Relative material cost | Baseline | ~1.3–1.6× |
| Relative machining cost | ~0.5–0.7× Grade 5 | Baseline |
Two lines are worth pausing on. Grade 2 has better corrosion resistance, not worse — alloying additions slightly reduce it. And Grade 2 machines roughly twice as easily, which on a complex part can matter more than the material price.
When Grade 2 is the right answer
Corrosion is the requirement and load is not. Chemical process piping, heat exchanger components, anodes, seawater fittings, desalination hardware, marine trim. If the part’s job is to not corrode, the cheaper and more corrosion resistant alloy is also the better alloy.
The part gets welded. Grade 2 welds readily. Grade 5 welds, but the weld and heat-affected zone lose ductility and the procedure needs proper inert shielding front and back. For a weldment, Grade 2 removes a category of risk.
The part gets formed. Grade 2 can be cold formed. Grade 5 largely cannot.
Stress is genuinely low. Brackets, covers, housings and spacers that carry almost nothing but must resist chemistry or must be non-magnetic and light.
Medical implants where the standard allows it. Grade 2 and Grade 4 are used for implant components where strength permits; Grade 23 ELI covers the high-strength cases.
When Grade 5 earns its price
Structural load. Anything carrying meaningful stress. Three times the yield strength is not a small margin.
Fatigue. Cyclic loading strongly favours Grade 5.
Threads and small load-bearing features. Grade 2 threads gall and strip at loads Grade 5 shrugs off.
Elevated temperature under load.
Weight-critical structure, where the strength-to-weight ratio is the whole reason titanium was chosen.
The grades in between
The choice is not binary.
Grade 9 (Ti-3Al-2.5V) sits in the middle — roughly 620 MPa yield, still weldable and formable, commonly used for tubing and hydraulic lines. It is underused by buyers who only know 2 and 5.
Grade 23 (Ti-6Al-4V ELI) is Grade 5 with reduced oxygen and iron for better fracture toughness and cryogenic performance. Standard for implants and some aerospace. More expensive and with tighter material availability.
Grades 7 and 11 add palladium for resistance in reducing acids where commercially pure titanium struggles.
Grade 12 adds molybdenum and nickel for crevice corrosion resistance at elevated temperature.
Machining, briefly
Both alloys share titanium’s fundamentals: low thermal conductivity, chemical reactivity, springback, and a hard requirement that the tool keeps moving and keeps a real chip load. Machining Ti-6Al-4V covers the parameters, and they apply to Grade 2 with speeds roughly 50–80 % higher.
Grade 2’s specific problem is that it is gummy. It builds up on the edge and tears rather than shearing, so finishes can be poor if the tooling is not sharp. Grade 5’s problem is heat and tool wear. Different complaints, same fix: sharp tools, adequate feed, pressure coolant.
For thin-walled parts, Grade 2’s lower stiffness makes deflection worse rather than better — see thin-wall titanium.
How to decide, in one question
What is the part being protected from — load, or chemistry?
If the answer is chemistry, start at Grade 2 and move up only if a stress calculation forces you. If the answer is load, start at Grade 5.
If the answer is both, say so in the RFQ along with the environment and the loads. That is the kind of question a supplier can help with before the drawing is frozen, and it is far cheaper to ask then than after the first article.
Background: titanium alloys.
Send the drawing and what the part does — if a cheaper grade will survive your application, we will tell you.