Titanium for airframes
starting with fabric and wooden materials, airframe materials have evolved into the current CFRP by way of aluminum alloys. Additionally, steel-based materials were used for portions where high strength was required (frames and joints), and have now been replaced by titanium alloys to save weight. Designing joints in an airframe where heterogeneous materials are used must take into consideration the prevention of potential difference corrosion (galvanic corrosion), and the elimination of strain caused by a difference in coefficients of thermal expansion. In recent years, as CFRP has come to the forefront, titanium alloys with physical characteristics similar to those of CFRP have become more commonly used.
Titanium for engines
Turbo fan engines are widely employed by commercial aircraft to improve combustion efficiency, and thereby improve fuel consumption. Fuel combustion in the rear section of the engine runs the gas turbine and fan blades in the fore section. Propulsion thrust is generated by the reaction force of the rearward flow of air taken in from the front by the blades, and the rearward discharge of combustion gases. Turbo fan engines of this type consist of four sections. They are, in order from the front: the fan, compressor, combustion chamber, and turbine. A titanium alloy is mainly used for the fan and the compressor in the fore half section, where the temperature is relatively low (600˚C or lower). For the turbine and the combustion chamber in the rear half section where temperatures are higher, a nickelbased alloy or iron-based alloy is used.