ok, i look through the few pages here quickly, but didnt see a topic referring to this question. Im wondering about the differences in titanium, ie: 3al/2.5v ...vs...6al/4v....now, being that aluminum is a stiffer material, will the 3% alum ti frame be more flexible than the 6% frame ? or is the alum placed in spots where it wont necessarily stiffen the frame, rather welds, etc ? also, where does vanadium come into play here? can anyone break this down for me? im looking into a possible custom frame (another story in itself) but want to choose the best, using that term lightly, material i can. Thanks!
Titanium material strengths? >........
- Thread starter ChrisNJ
- Start date
You're asking questions only an experienced metallurgist can answer. Sounds similar to the "is 6 or 7 series alu better" q's, it's all down to how they work the metal, not just the alloy of the original material.
My opinion: buy one with lifetime warranty, that way breakages and strength shouldn't be an issue.
My opinion: buy one with lifetime warranty, that way breakages and strength shouldn't be an issue.
from my basic understanding of Ti...
3/2.5 is more forgiving and flexible
6/4 is stronger and more rigid.
Take a look at the old Ibis BowTi. It used the 6/4 in places where they wanted it rigid, and 3/2.5 in the places it needed to flex.
Hope this helps.
-Brad
3/2.5 is more forgiving and flexible
6/4 is stronger and more rigid.
Take a look at the old Ibis BowTi. It used the 6/4 in places where they wanted it rigid, and 3/2.5 in the places it needed to flex.
Hope this helps.
-Brad
It doesn't work that way. In those percentages the alloying elements don't behave the way they would on their own. Basically, on a molecular level the Aluminum and Vandium atoms take up specific spots in the structure of the overall material, but are evenly distributed throughout.
6/4 is a stronger metal, unfortunately it is also harder to work with and doesn't come in extruded tubing. So 6/4 tubing is seamed tubing rolled from sheet, which is a crappy way to make tubing.
a 3/2.5 tube is much easier to manipulate and work with. This will be even more important in a custom frame. IMO, 6/4 is only advantageous for forged or machined-from-billet parts.
From the Metals Handbook (which conveniently sits on my desk)
Ti 6Al-4V Tensile: 130 ksi Yield: 120 ksi
Ti 3Al-2.5V Tensile: 90 ksi Yield: 75 ksi
The strengths of the alloys, however, don't tell the whole story. The guy from Ohio is correct about the basic function of the alloying elements (they take the place of Ti atoms in the atomic structure) and that's really all the detail you need to know about the structure of alpha-beta titanium alloys.
It really isn't too important which alloy is used to make your frame. From a pure strength-to-weight standpoint it looks like Ti-6-4 would be the better alloy, however, frame design is going to be much more important than the overall strength of the alloy. Tube wall thickness, tube diameter, gussetting, joining process and post joining heat treatment will have a far greater effect on the quality and durability of your frame.
The biggest killer of frames is fatigue failure. Whether your frame cracks due to fatigue is mostly related to the size of the defects in the welds, the stress at the welds, and the fracture resistance of the weld. You control the defects in the weld by using good welding practices, (cover gas, geometry, welder skill, cleanliness, etc.). You control the stress at the welds by using geometry, gussets and tube butting. Also, the amount of restraint applied during post weld heat treatment affects residual stresses in the welds. You control the fracture resistance of welds by controlling heat input during welding and using appropriate post-weld heat treatment to recover fracture toughness.
All of the above will be invisible to you as the consumer. In reality, the guy who suggested you buy the frame with a good reputation and a lifetime warranty is correct. You can't control the manufacture of your frame, so the best bet is to use the past performance of the company to judge the quality of their product. Of course you can't protect yourself against a welder having a bad day. That's what warranties are for.
Hope this helps a little.
Ti 6Al-4V Tensile: 130 ksi Yield: 120 ksi
Ti 3Al-2.5V Tensile: 90 ksi Yield: 75 ksi
The strengths of the alloys, however, don't tell the whole story. The guy from Ohio is correct about the basic function of the alloying elements (they take the place of Ti atoms in the atomic structure) and that's really all the detail you need to know about the structure of alpha-beta titanium alloys.
It really isn't too important which alloy is used to make your frame. From a pure strength-to-weight standpoint it looks like Ti-6-4 would be the better alloy, however, frame design is going to be much more important than the overall strength of the alloy. Tube wall thickness, tube diameter, gussetting, joining process and post joining heat treatment will have a far greater effect on the quality and durability of your frame.
The biggest killer of frames is fatigue failure. Whether your frame cracks due to fatigue is mostly related to the size of the defects in the welds, the stress at the welds, and the fracture resistance of the weld. You control the defects in the weld by using good welding practices, (cover gas, geometry, welder skill, cleanliness, etc.). You control the stress at the welds by using geometry, gussets and tube butting. Also, the amount of restraint applied during post weld heat treatment affects residual stresses in the welds. You control the fracture resistance of welds by controlling heat input during welding and using appropriate post-weld heat treatment to recover fracture toughness.
All of the above will be invisible to you as the consumer. In reality, the guy who suggested you buy the frame with a good reputation and a lifetime warranty is correct. You can't control the manufacture of your frame, so the best bet is to use the past performance of the company to judge the quality of their product. Of course you can't protect yourself against a welder having a bad day. That's what warranties are for.
Hope this helps a little.