ALTERING THE COOLING RATE DEPENDENCE OF PHASE-FORMATION DURING RAPID SOLIDIFICATION IN THE ND2FE14B SYSTEM

In order to evaluate the effects of additions on the solidification be havior of Nd2Fe14B, a stoichiometric alloy was modified with elemental additions of Ti or C and a compound addition of Ti with C. For each a lloy, a series of wheel speed runs was undertaken, from which the opti mum wheel speeds and optimum energy products were determined. On the B Hmax versus wheel speed plots, regions were identified in order to ana lyze the changes with cooling rates leading to phase formation brought about by the alloy modifications. The compilation of the regional dat a of the modified alloys showed their effects on altering the cooling rate dependence of phase formation. It was found that the regions of p roperitectic iron formation, glass formation, and the optimum cooling rate can be changed by more than a factor of two through appropriate a lloying additions. The effects of the alloy modifications can be visua lized in a convenient fashion through the use of a model continuous co oling transformation (CCT) diagram which represents phase formation du ring the solidification process under continuous cooling conditions fo r a wide range of cooling rates from rapid solidification to equilibri um cooling.