Self-propagating High-temperature Synthesis Of NiAl-TiC

In this paper, in-situ particle reinforced NiAl-TiC composites were Successfully fabricated by SHS using exothermic reactions in Ni-Al-Ti-C system. Investigations were thoroughly made in three aspects:thermodynamics and kinetics ,SHS process ,relation between microstructure .The reactive formation enthalpy, free energy and reactive adiabatic temperature of NiAl and TiC fabricated in Ni-Al-Ti-C system have been theoretically calculated and analyzed based on the first law of thermodynamics. The calculated results show that the NiAl intermetallics forms before TiC. NiAl and TiC are the final phases. The calculated results were verified by XRD. The experimental results are in good agreement with the theoretical analysis.Based on kinetic theories, the micro reaction process of Ni-Al-Ti-C system was studied by the analysis of XRD and SEM of the product after the SHS and DSC analysis. Following the law of smallest energy, with the propagation of combustion wave, NiAl intermetallics as a result of reaction of Ni and Al will form firstly. Subsequently, as the increasing of temperature, TiC phase form ultimately. In Ni-Al-Ti-C system liquid NiAl existed during reactions and it greatly increased the reaction area and improved the transportation of mass and energy, which underlies the characterization of high temperature and high velocity. On the other side, the existing time of liquid product played an important role in structure and the densification of product.The process parameters significantly influence the combustion synthesis procedure of NiAl-TiC system. Optimal process parameters have been gained by studying the influence of the process parameters on Microstructures of NiAl-TiC matrix composites,including ratio of reactants,green-compactpressure,diamete and preheating temperature. The parameters are defined by real tests. The best ratio of reactants is 20%TiC, green-compactpressure is 300MPa, diamete isΦ30mm×30mm , preheating temperature is 300℃.Microstructures of NiAl-TiC matrix composites show that it consists of near equivalent axis-shaped or ball-shaped ceramic phase and metal binder phase. The interface between reinforcement and metal binder is clean and no interfacial phases are found. TiC particles assembled on the boundary of matrix grams and the interspace between TiC particles was gradually filled by matrix while TiC content increased, thus the TiC distribution regions connected each other to form a net work that surrounded matrix grains. the composite is compact and there are a few pores in it.