Novel reactive, liquid phase processes and the development of advanced materials

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High temperature intermetallic compounds and metal-ceramic composites are difficult and costly to process using conventional casting, forming and machining routes due to their high melting temperature, high hardness and limited ductility. The fabrication of these materials through pressing and sintering of powders has the advantage of the fabrication of near net shape parts, reducing the need for forming and machining. For the specific case of reactive sintering (RS), the use of a mixture of relatively low cost pure powders, which react during sintering to form the desired compounds or composites, has the added benefits of lower processing temperatures and economic production. However RS suffers for the production of a porous, inhomogeneous finished product which has limited the commercial application of this technology. Our recent studies on RS of NiTi shape memory alloy (SMA) has revealed that low sintered densities result from the development of a poorly distributed liquid phase which becomes isolated into discontinuous "pockets".