The use of titanium
was largely spurred on by the aerospace industry after WWII, which
sought stronger materials than the aluminum alloys they were using,
while maintaining the stringent requirements for weight. Titanium
is extremely difficult to process, which accounts for its high price.
Like most metals, titanium is combined with alloying elements to make alloys of titanium that are stronger and have other useful properties. The two most common for aerospace applications are Ti 6-4 (6% Aluminum, 4% Vanadium, 90% Titanium), and Ti 3-2.5 (3% Aluminum, 2.5% Vanadium, and 94.5% Titanium). Ti 3-2.5 was created specifically to make high strength tubing, while T- 6-4 was created for structural components in airframe applications. Titanium is extremely corrosion resistant. In fact, it can be used without painting the bare metal because it does not rust or corrode like steel frames or aluminum exposed to rock salt. This means you never have to worry about your titanium frame falling apart due to exposure to the weather.
The Ti 3-2.5 tubing is the same high strength material used in the most advanced
aerospace applications. It is drawn seamless tubing, which can be welded to join
the tubes of the bike frame together. The tubes are cold worked to provide additional
strength to the material, and through this process is tailored to provide the
correct shape tubing for the frame design. This provides an extremely lightweight
and strong racing machine, where the geometry of the frame is tailored by working
the tube sets to create the perfect ride.
3Al/2.5V Titanium Tubing Properties
135,000 psi ( 930 Mpa) Ultimate Strength
115,000 psi ( 790 Mpa) Yield Strength
About 10 - 15% stronger than Cr-Mo steel
And three times as strong as 6061 Al - T6
0.162 lbs/in_ (4.48 gm/cm_)
45% lighter than steel and 65% heavier than aluminum
Based on Yield Strength divided by Density
74% higher than 6061 - T6 Aluminum
102% higher than 4130 Cr-Mo steel
(the most common form of steel used in bike frames)
15.0 x 106 psi (10.3 x 104 Mpa)
50% higher than aluminum alloys and
50% lower than steel alloys
Excellent in all natural water and saltwater environments
Unlike steel, titanium will never rust and
will not pit, corrode or deteriorate in salt water like
Titanium has good fracture Toughness
Ti resists damage from impact unlike composite materials
Excellent for both high and low cycle fatigue.
Titanium is a metallic element whose unique properties including high strength, low density, excellent fatigue and corrosion resistance and low modulus make it the ideal material for bicycle frames. Developed primarily for the aerospace industry, titanium alloys have also found a growing use in Medical, Petrochemical, Pulp and Paper, Architectural, Naval and Sports applications. Titanium itself is not rare but actually very abundant with large deposits occurring in Australian beach sand. However, titanium's extreme reactivity with oxygen makes it difficult to produce in metallic form and it is a long and expensive process to create the seamless tubes used in frame construction.
Utilizing an alloy of titanium with 3% aluminum and 2.5% vanadium, known as Ti-3Al-2.5V or simply Ti-3-2.5 for all of the tubing frame members. This alloy was developed for use in high pressure hydraulic lines and is found on virtually all new commercial and military airplanes being built. Ti-3-2.5 is a balance between the higher strength but less ductile titanium alloys used in aerospace and commercially pure titanium grades which do not offer enough strength to be used in thin-walled tubes.
The high strength and low density of this alloy allow for the building of frames that are not only light weight but also extremely strong and durable. Titanium does not break down, rust or corrode in any type of atmospheric environment and it's high fracture toughness and fatigue resistance result in a frame that can take a pounding and will not fail.
Another unique property of titanium is it's low elastic modulus. The elastic modulus is a measure of how stiff a material is and is directly related to a material's ability to transmit shock waves. Titanium's low modulus translates into a natural dampening effect on vibrations and shocks which allows titanium frames to have a smooth ride even without additional suspension elements. The combination of titanium's high strength and low modulus make the material very "springy" and in fact aircraft springs were one of the first uses for titanium alloys. Because of this spring like effect, the material allows for good energy transfer and does not sap energy from the rider like a suspension system or weaker frame materials will.