When the aircraft was just invented, it was basically made of wood,
canvas and steel wire, which were used in the early stage of World War
II; after World War II, jet aircraft began to use aluminum magnesium
alloy as the main body to make the skeleton and skin outside the main
girder. In modern times, composite materials are used more and more.
However, composite materials are not suitable for all parts of aircraft.
Another titanium alloy basically replaces the original position of
aluminum magnesium alloy. Today's major jet aircraft can be made without
a little aluminum and magnesium alloy, but not titanium alloy. Titanium
is an important structural metal developed in 1950s. Titanium alloy has
high strength, good corrosion resistance and high heat resistance. In
aviation manufacturing, high temperature titanium alloy for aeroengine
and structural titanium alloy for airframe are mainly developed. High
temperature titanium alloy is mainly used to make fan and compressor
parts of aircraft engine, followed by rocket, missile and high-speed
aircraft structural parts. The melting point of pure titanium is 1725 ℃.
The density of high strength titanium alloy is generally 4.51 g / cm3,
Only
60% of steel. Although it is significantly larger than 2.7 grams per
cubic centimeter of aluminum alloy. However, the structural strength,
heat resistance, low temperature resistance and corrosion resistance of
titanium alloy are incomparable to aluminum alloy. High strength
titanium alloys exceed the strength of many alloy structural steels.
Therefore, the specific strength of titanium alloy is much higher than
that of other metal structural materials. For example, the pressure hull
of Jiaolong is made of titanium alloy, which can withstand the water
pressure of more than 7000 meters in the deep sea. The smaller titanium
alloy pressure hull can submerge to a depth of 11000 meters. Even in
special steels, only martensitic high strength steels can do this.
Therefore, titanium alloy parts have high unit strength, good rigidity
and lighter weight than steel. Titanium alloy can be used in engine
components, framework, skin, fasteners and landing gear of aircraft. The
working temperature of aluminum alloy is more than 200 ℃, while that of
titanium alloy can reach 500 ℃. High altitude high-speed flight will
produce a lot of friction heat energy, so the flying objects flying
above three times the speed of sound will have a large amount of
friction heat,
Titanium alloy is needed as framework and skin to
resist thermal barrier effect. Titanium alloy is extremely
corrosion-resistant, almost not afraid of seawater, even sulfuric acid,
nitric acid strong corrosion, this is any steel and aluminum alloy can
not reach the ability. Steel will not only soften and anneal rapidly at
high temperature, but also become brittle at ultra-low temperature.
However, the metallicity of titanium alloy is still basically normal at -
253 ℃, which is also very rare. Titanium alloy is the first widely used
in aviation manufacturing developed countries. For example, for the
typical f22a, 41% of the aircraft's empty weight is titanium alloy. In
the early high-altitude and high-speed flying UAVs, there are titanium
alloy consumption as high as 90%. For example, I had contact with a
special high-altitude high-speed UAV that crashed in the jungle by a
superpower in the early years. Hanhai Langshan (Xiongnu Langshan)
believes that this is the first time that its titanium alloy has been
used in advanced aircraft. At that time, J6 and J7, as the main
fighters, had almost no titanium alloy parts. In J8 series, about 2%
titanium alloy was used for the first time. HY helicopter was introduced
in 1980s, because of its outstanding performance, there was a plan to
imitate it for a long time. However, this kind of helicopter also used a
lot of titanium alloy, which completely exceeded the basic industrial
capacity at that time. So we have to give up.
But the stars have
changed. Up to now, the output of titanium alloy has been the first in
the world. At present, almost all self-made military and civil aircraft
use titanium alloy and composite materials in large quantities, which is
basically in line with the world's advanced level. In addition to the
aviation industry, the amount of titanium alloy used in shipbuilding
industry is also very large, which is one of the reasons why all kinds
of black fish gradually reach the world advanced level.
