Advantages and disadvantages of titanium alloy fasteners and their applications

The density of titanium alloy is generally about 4.5g/cm3, which is only 60% of steel. The strength of pure titanium is close to that of ordinary steel. Some high strength titanium alloy exceeds the strength of many alloy structural steel. Therefore, the specific strength (strength/density) of titanium alloy is far greater than other metal structure materials, can be made of high unit strength, good rigidity, light components. Titanium is currently used in aircraft engine components, skeleton, skin, fasteners and landing gear.

Titanium alloys exhibit superior corrosion resistance in harsh environments, which is the main reason why they are used in the manufacturing of chemical equipment. It has good high and low temperature characteristics, non - magnetization and low thermal conductivity and thermal expansion coefficient. On the negative side, titanium fasteners are very difficult to manufacture. And when the installation of threaded fastener and locking, threaded easily abrade or get stuck dead. Here are some examples of titanium alloys that are sensitive to stress corrosion at moderate temperatures. But this situation can be alleviated by some special techniques.

Pure titanium is not heat-treatable. In general, almost no fasteners are made of pure titanium. There are many titanium alloys, most of which are proprietary. The results show that only a small part of planed titanium alloy is suitable for fabricating threaded fasteners. Ti-6Al-4V is a heavy duty alloy. This titanium alloy fastener has a minimum tensile strength of 135,000 psi, providing high strength and satisfactory toughness.Ti-6Al-4V has great creep resistance and is easy to cast. The strength characteristics of Ti-6Al-4V alloy are similar to that of Ti-6Al-4V alloy, but the toughness is slightly worse. The tensile strength of Ti-1Al-8V-5Fe is approximately 200,000 psi. Overstated by its outstanding strength-to-mass ratio, the fastener made of this alloy holds as fast as a steel fastener of the same quality with a tensile strength of 350,000 psi. Two other titanium alloys, Ti-6Al-12Zr and Ti-6Al-6V-2Sn, are sometimes used in fasteners.

The most attractive property of titanium is its extremely high strength-to-mass ratio. Their mass is only 57 percent of that of steel by volume, yet their strength is comparable to that of a heat-treated iron-carbon alloy. Titanium is ideal for aerospace, jet aircraft and missiles. But its biggest drawback is that it is too expensive. The use of titanium as a fastener material is discouraged unless there is no alternative.