In situ processing for TiC-Al composite by dipping exothermic reaction process

Abstract

Owing to the rapid advancement of composite materials technology, composites are not only replacing conventional materials in many applications but also creating new areas unique to themselves. In recent year, Metal/ceramic composites are even more attractive because they have improved properties over conventional materials and are relatively simple to fabricate. Recently, in situ processes for metal matrix composites have emerged as novel processing techniques. In situ techniques involve a chemical reaction resulting in the formation of a very fine and thermodynamically stable reinforcing ceramic phase within a metal matrix. In particular, the reinforcement surfaces are likely to be free from contamination and a strong bonding between matrix and reinforcement can be achieved. Aluminum composites have a great potential because of their high strength-to-weight ratio. The TiC-Al composite system has been studied by a number of researchers, which shows high strength, high wear resistance and high stiffness. The TiC-Al composite can be made either by adding TiC powders directly to the melt, or by in situ reactions between carbon sources such as $Al_4C_3$ particles and $CH_4$ gas in Al-Ti melts. In addition, the XD process could make the in situ TiC-Al composite by using an exothermic reaction. It is well known that the strength of metal matrix composites can be increased by suitably controlling the dispersion parameter, i.e. either by increasing the volume fraction or by decreasing the particle size of reinforcement. However, the processing of composites with high volume fractions (greater than 30vol.%) of reinforcements is difficult and usually lead to structures with defects (cavities and cracks). In this Ph.D. thesis, it was suggested that high volume TiC reinforced aluminum composites could be synthesized by using a dipping exothermic reaction process (DERP) as a newly suggested process technique. DERP involves exothermic reactions like other in-s...