ChemInform Abstract: Precipitation Phenomenon in Stoichiometric Nd2Fe14B Alloys Modified with Titanium and Titanium with Carbon.

Abstract

Abstract Precipitation phenomenon has been investigated in stoichiometric Nd2Fe14B alloys modified with Ti and Ti with C. Precipitates can be used to inhibit grain growth and understanding the precipitation process is important in order to form the most effective dispersion. In the NdFeBTi system, TiB2, and in the NdFeBTiC system. TiC are found to be the precipitating phases. Depending on composition, the precipitates can form at high temperatures in the liquid, during cooling after solidification, and during heat treatment. The precipitates form on grain or phase boundaries. The TiC precipitates typically form as discrete particles while the TiB2 precipitates form generally in a globular bunched-up fashion. After a homogenization heat treatment, the equilibrium solubilities of Ti and Ti with C in the Nd2Fe14B phase are found to be 0.47 wt.% and ⩽0.06 wt.% respectively. This means that almost all of the alloyed Ti and C can be precipitated as TiC which returns the excellent intrinsic magnetic properties of the hard magnetic phase. Both the carbides and the borides are found to have excellent high-temperature stability and resist coarsening and dissolution at least to 1000°C. Since Ti and C react to form TiC the amount of hard magnetic phase is not reduced while Ti addition alone reacts with boron and reduces the amount of hard magnetic phase if extra boron is not added.