SOLUBILITY OF TI WITH C IN THE ND2FE14B SYSTEM AND CONTROLLED CARBIDEPRECIPITATION

An investigation has been launched to understand the unique solubility of titanium with carbon in the Nd2Fe14B system. In order to restrict grain growth effectively, a stable dispersion of many fine precipitate s must be formed. In order to form an effective dispersion, the solubi lities of the precipitating elements should be understood. This includ es the liquid and solid solubilities as well as the equilibrium and no n-equilibrium solubilities. Samples made by ingot casting and melt-spi nning were examined. The solubility limit of titanium and carbon in th e liquid phase was found to be between 4 and 6 at.% Ti+C. Once the sol ubility limit of the liquid is exceeded, primary TIC precipitates form in the liquid at high temperatures. The maximum solid solubility in t he 2-14-1 phase depends on the existence of other phases and is found to be cooling-rate-dependent. For TiC, the solid solubility is found t o equal the liquid solubility. The cooling-rate dependence indicates t hat the titanium and carbon exist in supersaturated solid solution. Th e equilibrium solubility in the 2-14-1 phase is found to be less than or equal to 0.06 wt.% Ti. Owing to its favorable solubility, TiC is fo und to be an exemplary alloying addition in the Nd,Fe,,B system, and c an be used to alter beneficially the extrinsic properties of the micro structure while maintaining the excellent intrinsic properties of the hard magnetic phase.