Applications Of Α-titanium Alloys, Α+Β-titanium Alloys, Β-titanium Alloys.

The most commonly used of the three titanium alloys are α-titanium alloys and α+β-titanium alloys; α-titanium alloys have the best cutting and machinability, α+β-titanium alloys are the next best, β-titanium alloys are the worst. α-titanium alloys are coded TA, β-titanium alloys are coded TB, and α+β-titanium alloys are coded TC.

Titanium alloys can be divided into heat-resistant alloys, high-strength alloys, corrosion-resistant alloys (titanium-molybdenum, titanium-palladium alloys, etc.), low-temperature alloys, special functional alloys (titanium-iron hydrogen-storage materials) and titanium-nickel memory alloys). The composition and properties of typical alloys are shown in the table.

Heat-treated titanium alloys can be adapted by adjusting the heat treatment process to obtain different phase compositions and microstructures. It is generally believed that the fine isometric organization has good plasticity, thermal stability and fatigue strength; the acicular structure has high durability, creep strength and fracture toughness; and the mixed isometric acicular structure has better overall properties.

Titanium is a new type of metal. The properties of titanium are related to the content of impurities such as carbon, nitrogen, hydrogen and oxygen. The impurity content of the purest titanium iodide is not more than 0.1%, but its strength is lower and plasticity is higher. 99.5% industrial pure titanium has the following properties: density ρ=4.5g/cm3, melting point 1725℃, thermal conductivity λ=15.24W/(mK), tensile strength σb=539MPa, elongation δ=25%, sectional shrinkage ψ=25%, modulus of elasticity E=1.078 × 105MPa, hardness HB 195.

The density of titanium alloy is generally around 4.51g/cm3, only 60% of steel. The density of pure titanium is close to that of ordinary steel. The strength of some high-strength titanium alloys exceeds that of many alloyed structural steels. Therefore, the specific strength (strength/density) of titanium alloys is much greater than that of other metallic structural materials. Parts with high unit strength, good rigidity, and light weight are shown in Table 7-1. Titanium alloys are used for aircraft engine components, skeletons, skins, fasteners, and landing gear.