Titanium Properties

Strength to Weight Ratio

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)

Elastic Modulus

15.0 x 106 psi (10.3 x 104 Mpa) 50% higher than aluminum alloys and 50% lower than steel alloys.

Corrosion Resistance

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 aluminum alloys.

Strength

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

Density

0.162 lbs/in_ (4.48 gm/cm_)
45% lighter than steel and 65% heavier than aluminum.

Toughness

Titanium has good fracture Toughness. Ti resists damage from impact unlike composite materials.

Fatigue Resistance

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.
Van Nicholas utilizes 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

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.

Figure 1 shows the ranges for specific stiffness and strength of some common bicycle frame materials. On this plot, the best material will be one that has high specific strength and high specific stiffness. We can see that titanium appears to be an excellent choice in this regard. Titanium is also one of the materials that exhibit a fatigue limit, although it may not be as well defined as steel. On the other hand, aluminum does not have a fatigue limit, and therefore aluminum bicycle frames can fail due to metal fatigue after a long enough time.

Van Nicholas frames are created by welding the tubes together with Commercially Pure (CP) titanium as the filler material in the TIG (Tungsten Inert Gas) weld process. Other frame manufacturers use Ti 6-4 as the filler, which can lead to a brittle weld due to an increased HAZ along the weld area. By welding the frames with CP titanium, the material does not have to be heated quite as high as would be needed if using Ti 6-4, and therefore the actual tubes of the frame are not melted together but rather adhered together with the CP Ti. This produces a stronger weld and therefore a stronger frame.


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