Porous NiTi alloy prepared from elemental powder sintering

An elemental powder sintering (EPS) technique has been developed for the 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 temperature, sintering time, and TiH₂ content) on the porosity, pore size, and pore distribution as well as phase composition in experimental alloys are investigated. It is found that in order to avoid the formation of carcinogenic pure Ni phase, the porous NiTi alloy should be synthesized over a temperature of 1223 K. This gives NiTi as the main phase without any elemental phase. Substitution of Ti by TiH₂ is more economic and more favorable to obtain homogeneous porous NiTi alloy. A proper selection of initial powders, ball-milling, pressing, and sintering process makes it possible to achieve the porous NiTi alloy with desired properties.