No Pressure Infiltration B <sub> 4 </ Sub> C / Al Composite Material Technology

In this thesis, fabricating boron carbide and aluminum ceramic -metal composites by pressureless infiltration technology, heat treatment of boron carbide and aluminum composites and their influence on the mechanical properties of the composites have been investigated. The microstructure of the material, its interface and their relationship with the properties are also been investigated.In the process of alloy melt and infiltrate the boron carbide, reaction between the boron carbide and aluminum interface occur, the key of achieving a good interface bond is the control of the reaction between the boron carbide and aluminum interface. The researches indicate that after a heat treatment at high temperature (1700癈), the chemistry properties of the boron carbide surface are changed. The new boron carbide surface, react weaker with aluminum, thus a better infiltration can be achieved.The influence of the infiltration temperature, the infiltration atmosphere and different kinds of aluminum alloys are investigated. The researches indicate that during the pressureless infiltration process, the atmosphere and temperature are necessary conditions. Too much oxygen content in the atmosphere will oxide the boron carbide surface, the infiltration will not occur. At too low too low infiltration temperature, the wettability between the boron carbide and aluminum are so poor that the infiltration will not occur too. All kinds of aluminum alloy in this study infiltrate the boron carbide preform, but the pure aluminum infiltrated the preform most completely.The mechanical test of the composites fabricated in different infiltration time and made of different aluminum alloys prove that in the selected technology conditions, the B4C/A1 composites have a better mechanical properties.After a long time of post infiltration heat treatment, a great deal of AlaBC is produced in the boron carbide and aluminum composites and the hardness of the composites increases greatly. The effect of the heat treatment time and heat treatment temperature on the composites constitutes and the mechanical properties are also beenstudied.The microstructure and the reaction of the interface are analyzed. The mostly products in the interface are AbBC which grows along the boron carbide and the boron carbide are attacked by the aluminum. The reaction between the boron carbide and aluminum interface changes the properties of the composites during the post infiltration heat treatment.