| Boron carbide is a promising material with unique properties such as extremely high hardness, low density and strong neutron absorption. Its brittleness, however, restricts its widespread use. This problem can be significantly reduced by the production of B4C-based composites. Boron carbide–aluminum composites have the potential to combine the high stiffness and hardness of B4C with the ductility of Al, so have an important application in the light armor plates. An infiltration technique is commonly used for the fabrication of B4C–Al composites. The wetting of molten B4C by molten Al is of crucial importance in producing the composites.In this work, the wettability of Al and Al alloys on B4C substrates was studied by the sessile-drop method, and the interfacial characteristics of B4C/Al were investigated by using scanning electron microscopy (SEM) , energy dispersive analysis of X-rays (EDX) and X-ray diffraction (XRD) analysis. In sessile drop experiments,the contact angles of Al and Al alloys with Ti on B4C substrates were investigated as a function of temperature. The wettability was very poor at temperatures near the melting point of Al (660℃). Al began to wet the B4C just above 1000℃and the contact angle was 90°. When the temperature were 1200℃and 1300℃, the contact angles of B4C/Al can be decreased to 40°and 20°respectively.. The addition of Ti can effectively improves wetting of the Al on B4C surfaces, and compared with pure Al, the contact angles of B4C/( Al-Ti) at 1200℃and 1300℃can be reduced to 0°. SEM and XRD results showed that there existed a reaction layer in the interface of Al and B4C, and the main products in the layer were AlB12C2 ,TiB2 and TiC. The wettability can be promoted by the reation of Ti and B4C because of the heat evolved during the reaction.At the same time, another major limitation to widespread use of B4C arises from its poor machining property. In this thesis, a new technology was developed by using the laser technology and acquired more achievements. The work principle and characteristics of the laser technology are detailed in this paper. And two kinds of cutting methods were designed to cut the boron carbide substrates. Based on the experiments, the effect of the technical parameters,such as laser energy,cutting speed and the laser beam quality, on the cutting quality were discussed. The fracture in all kinds of incision crafts were analyzed by scanning electron micrograph(SEM) and the cutting mechanism was also discussed.The cutting experiments were carried out on a Nd:YAG laser. Experimental results showed that the laser techonolgy can be used in the thick B4C substrates. The relation between laser energy, and thickness was that higher laser energy was required for the higher cutting speed and thicker substrates. Higher laser energy and smaller diameter of laser beam can promote the cutting quality and cutting ability of laser. In the experiments, the thick boron carbide,5.54mm thick, under the 130w Nd:YAG laser output,can be separated by scanning along the desired cutting path twice, and the maximum cutting speed can be reached is 120mm/min.For the 10.1mm thick boron carbide substrate ,however, the laser cutting energy must be increased to 170w and the maximum cutting speed was 100mm/min. Meanwhile, the most important adventage of this method is the ceramic can be cut without any fracture.The laser cutting mechanism can be described as follows. In the first stage, the fracture is initiated due to the tensile stress at the edge of the specimen. In the second stage, the stress near the laser spot is highly compressive of creep deformation. After the passage of the laser beam, the compressive stress will be relaxed,which then induces a residual tensile stress, making the fracture grow from upper surface to lower surface of the substrate. The final stage is unstable fracture, the stress near the crack tip is a completely tensile stress through the thickness direction, and the substrate will be separated.
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