The Preparation, Structure And Properties Of TiC/Ni₃Al Composites

In this thesis, TiC/NisAl composites have been prepared by the pressureless infiltration technique, and its influences on the mechanical properties of the composites have been investigated. The microstructure of the composites have been investigated by using a series of techniques, such as OM, SEM, XRD, XPS, etc. The mechanical properties of the composites have been tested. In addition, the effects of the microstructure on the mechanical properties have been studied.There are many defects in the TiC preforms prepared by cold pressing, such as small air holes and cracks. The TiC preforms prepared by hot pressing have better qualities. The sintering between TiC powders can make the TiC preforms with network structure.Ni3Al has a good wettability with TiC. In purified argon atmosphere, melt Ni3Al can infiltrate TiC preforms spontaneously. During the pressureless infiltration process, the atmosphere and temperature are necessary conditions. TiC/Ni3Al composites have been prepared using upward infiltration method. The densification was performed by both Ni3Al melt filling and TiC sintering during the infiltration.The microstructure of infiltrated samples were assessed by both optical and electron scanning microscopy. TiC particles joined each other due to sintering, and a dense and continuous microstructure was seen in pictures of the broken surface. The interface of TiC/Ni3Al composites is weak. The cracks may be due to the thermal expansion mismatch between TiC reinforcement and Ni3Al matrix.TiC/Ni3Al composites processed by upward infiltration had a flexural strength of 935 MPa and a fracture toughness of 20.41 MTSfnf3'2 in room temperature. In 1100, the highest flexural strength of 655 MPa had been gained.Without small air holes or cracks defects, TiC/Ni3Al composites prepared by pressureless infiltration can have better mechanical properties. Dense and continuous network microstructures are important for better mechanical properties of composites.