POROUS NITI ALLOY PREPARED FROM ELEMENTAL POWDER SINTERING

An elemental powder sintering (EPS) technique has been developed for t he synthesis of porous NiTi alloy, in which Ni and Ti powders are used as the reactants and TiH2 powder is added as a pore-forming agent and active agent. Effects of various experimental parameters (sintering t emperature, sintering time, and TiH2 content) on the porosity, pore si ze, and pore distribution as well as phase composition in experimental alloys are investigated. It is found that in order to avoid the forma tion of carcinogenic pure Ni phase, the porous NiTi alloy should be sy nthesized over a temperature of 1223 K. This gives NiTi as the main ph ase without any elemental phase. Substitution of Ti by TiH2 is more ec onomic and more favorable to obtain homogeneous porous NiTi alloy. A p roper selection of initial powders, ball-milling, pressing, and sinter ing process makes it possible to achieve the porous NiTi alloy with de sired properties.