Compared with non-metal-based composites, the potential of metal-based composites has not been fully exerted, with a narrow application range and few mature varieties. This situation did not improve slightly until the mid-197s. In 1974, the American Bureau of Materials Consulting affirmed the correctness of the development and use of metal matrix composites for the first time, and said that it should pay attention to and support this work. This is mainly a series of strict requirements put forward by the development of aviation, aerospace and energy industry, which seems to be solved only by relying on metal matrix composites and fine ceramics. In addition to graphite and boron (borosilicate) fibers, reinforcing agents used in metal matrix composites also include high-strength steel wires, high-melting alloy wires (tungsten and molybdenum) and whiskers (alumina and silicon carbide). These fibers are used to form composite materials with Al, Mg, Ti, Cu and Ni-Co based superalloys respectively.
the development of boron-aluminum composites started at the earliest and achieved certain results. This material can be used in the middle fuselage frame tube of the space shuttle, which can reduce the weight by 8 kg. There are only a few planes made of boron-aluminum composite materials, such as F-111 and S-3A, and there are also the shells of Atlas missiles.
The most promising potential application of boron-aluminum composite material is to manufacture compressor and fan blades of jet engines. If it is used instead of titanium alloy, the weight can be reduced by 33% and the cost can be saved by about 45%. Several major American engine companies such as Pratt? Whitney, General Electric, TRW, etc. have done research on boron-aluminum composite fan blades. The boron-aluminum compressor blade was tried on JT8D engine, and the working temperature reached 3℃. In addition, the beryllium-aluminum compressor blade was tried on TF-41-P3 engine.
Graphite-aluminum composites also have high specific strength and modulus, and are suitable for helicopters, missiles, tanks and assault pontoons. The transmitter of CH47 helicopter adopts multilayer graphite-aluminum fender, which greatly reduces vibration and noise. In addition, graphite-aluminum and graphite-magnesium will be used in artificial satellites and large-scale space structures, such as satellite support frame, planar antenna body and foldable parabolic antenna.
Ni-based and Co-based superalloys are reinforced with high-melting-point molybdenum and tungsten wire whiskers to become heat-resistant composites. This work has been carried out in many countries for many years in order to meet the needs of advanced turbine engines with increasing working temperature and load. The solid turbine blades made of this heat-resistant composite material can increase the temperature and revolution of the turbine, reduce the number of turbine stages and the consumption of cooling gas, and create conditions for improving the engine. Tungsten wire reinforced composites with thorium dioxide and hafnium carbide are used, and the working temperature is 116 ~ 12℃, which is at least 1℃ higher than the current turbine working temperature.
Molybdenum and tungsten with melting point reinforced by alumina whisker felt or single crystal fiber can withstand higher temperature, and its strength at 165℃ is twice that of tungsten, so it has passed the test as a rocket nozzle material.
Various laminates based on steel plates are also a general composite material. For example, a stainless steel-clad aluminum plate used in Boeing 767 and 757 aircraft can replace titanium alloy as a fire retardant material for engines, which is light in weight and low in price.
the other is a three-layer composite material with steel plate as the base, porous bronze as the middle layer and PTFE plastic as the surface layer, which can be used to manufacture truck chassis bushings, machine tool guide rails and bearings working in high-temperature corrosive media.
Superconducting cable is also a kind of composite material, which is composed of copper-tin alloy as the matrix and 295 niobium wires buried. After diffusion treatment, Nb2Sn metal compound with a thickness of seven microns is formed at the interface. It has superconductivity and can be used to manufacture new products such as maglev high-speed trains, nuclear fusion reactor electromagnets, energy storage superconducting inductors and superconducting generators.