Modern aircraft have a maximum speed of 2.7 times the speed of sound. Flying so fast at supersonic speed, the plane will rub against the air and generate a lot of heat. At 2.2 times the speed of sound, aluminum alloys can't stand it. Will High temperature resistant titanium alloy shall be used. When the thrust-weight ratio of aero-engine increases from 4 ~ 6 to 8 ~ 10, and the compressor outlet temperature increases correspondingly from 200 ~ 300℃ to 500 ~ 600℃, the original low-pressure compressor disc and blade made of aluminum must be converted to titanium alloy.
In recent years, scientists have made new progress in the research of properties of titanium alloys. Originally titanium alloy composed of titanium, aluminum, vanadium, the highest working temperature is 550℃ ~ 600℃, and the new aluminum titanide (TiAl) alloy, the highest working temperature.
The temperature has been raised to 1040℃.Using titanium alloy instead of stainless steel to make high-pressure compressor discs and blades can reduce the structural weight. For every 10% reduction in weight, the aircraft saves 4% fuel. For a rocket, each 1kg weight loss adds 15km to its range.
Why do aircraft have to be made of titanium alloy? Titanium alloy aircraft landing gear parts, first of all, titanium alloy thermal conductivity is low, only steel 1/4, aluminum 1/13, copper 1/25. Due to slow heat dissipation in the cutting area, not conducive to thermal balance, in the cutting process, heat dissipation and cooling effect is very poor, easy to form high temperature in the cutting area, plus.
After work, the deformation of parts rebound, resulting in cutting tool torque increase, cutting edge wear fast, durability reduced. Secondly, the low thermal conductivity of titanium alloy, so that the cutting heat in the small area near the cutting knife is not easy to send out, the front knife friction increased, not easy to remove chip, cutting heat is not easy to send out, accelerate tool wear. Finally, the chemical activity of titanium alloy.
High, in high temperature processing and tool material reaction, formation of dissolution, diffusion, resulting in sticking knife, burning knife, broken knife and other phenomena.
