The choice of metal matrix has a decisive effect on the properties of composite materials. The density, strength, plasticity, thermal conductivity, conduction, heat resistance and corrosion resistance of metal matrix will affect the specific strength, specific stiffness, heat resistance and thermal conductivity of Composite Materials , Conductive sound performance. Therefore, in the design and preparation of composite materials, should take full account of the gold matrix of the chemical and physical properties and compatibility with the reinforcement and so on.
The choice of metal matrix should be considered in three ways: the requirements, material composition and composite effect.
1. Use requirements: According to the application areas and working conditions to select the substrate. Such as aerospace applications, high specific strength and high modulus and dimensional stability is the most important performance requirements; as aircraft and satellite components should choose a small density of light metal alloys (such as magnesium, aluminum alloy) as a matrix than High strength, high modulus graphite fiber, boron fiber and other components of graphite / magnesium, graphite / aluminum, boron / aluminum composite materials. Aircraft engine not only requires high specific strength and high modulus, but also requires high temperature, high temperature, oxidizing atmosphere in the normal work, you should choose a good temperature of titanium alloy, nickel alloy and intermetallic compounds as a matrix material, Such as silicon carbide / titanium, tungsten / nickel-based superalloy composite materials can be used for jet engine blades, shaft and other important parts, automotive engine parts required heat, wear, heat, have a certain high temperature strength, (Short fiber) / aluminum composite material, such as silicon carbide particles / aluminum composite material, carbon fiber or alumina short fiber / aluminum composite material, such as silicon carbide particles / aluminum composite material, carbon fiber or alumina short fiber / aluminum composite material Composite Materials can be made engine piston, cylinder and other parts.
From the use of temperature considerations, aluminum and magnesium composite materials forging in the range of 350 ~ 500 ℃, titanium matrix composite materials can be used for 650 ~ 900 ℃ range, and nickel, cobalt-based superalloy and intermetallic compound based materials can be Above 1000 ℃ use.
2. Material composition: different enhanced forms (continuous fiber reinforced or discontinuous reinforcement), and different reinforcing Composite Materials on the substrate selection also has an impact.
For the continuous fiber reinforced composite material, the main consideration of the selection of the matrix is to give full play to the advantages of reinforcing fiber performance, the matrix and the fiber has good compatibility and plasticity, and does not require the matrix itself has a high strength and modulus The Experiments show that the high strength and high modulus of the alloy material, and the combination of enhanced fiber effect is sometimes not as good as a forging alloy material, so the advantages of fiber is not fully play. For example, continuous carbon fiber reinforced aluminum composite materials, aluminum or aluminum alloy with a small amount of alloy elements as a matrix than the high-strength aluminum alloy effect is better, the higher the strength of aluminum, the composite material performance is not necessarily good.
On the contrary, for non-continuous reinforced (particle, whisker, short fiber) metal matrix Composite Materials, the strength of the matrix has a decisive effect on the composite material, therefore, to choose a higher strength alloy as a matrix, which is continuous fiber reinforced metal The matrix selection of the composite is different. Such as particle reinforced aluminum composite materials Yin selected high-strength aluminum alloy as the matrix.
3. Compound effect: composite effect depends mainly on two factors, one material, the second is the process. From the material point of view, the main requirements of the metal matrix and enhance the good compatibility.
The compatibility of the metal matrix with the reinforcement depends on their chemical composition and properties. Usually the metal matrix often contain different types of alloying elements, these alloying elements and the reinforcement of the degree of reaction is different from the reaction reaction products generated after the reaction: the resulting formation of the chemical composition of the interface is not the same, the ability to withstand the load But also in the external force will be part of the interface first damage, causing cracks in the expansion, resulting in the overall performance of composite materials decreased. Therefore, in the selection of matrix alloy should pay full attention to chemical composition, contains the alloy is not conducive to both the metal and reinforced infiltration complex, but also conducive to the formation of a stable interface.
Such as carbon fiber reinforced aluminum composite materials, in the pure error by adding a small amount of titanium, zinc and other alloying elements can significantly improve the interface structure and properties of the interface, greatly improving the performance of composite materials.
Another example is the use of carbon fiber as a reinforcement. It is not appropriate to use iron and nickel as the matrix. Because iron and nickel elements at high temperatures can effectively promote the carbon fiber graphitization, destruction of the carbon fiber structure, so that the loss of the original strength, so that the degradation of composite properties.
The choice of the matrix is mainly to ensure that the excellent performance of the reinforcement is fully exerted, therefore, the best structural alloy is not necessarily the best matrix alloy. This is because the combination with the reinforcement, the interface reaction and the stability of the interface phase than the performance of a single matrix is more important.