Evidence for elemental partitioning in gas-atomized Nd2Fe14B modified by alloying additions

Measurements of the Curie and spin reorientation temperatures provide infor mation about elemental partitioning as a function of effective quench rate in Nd2Fe14B-based powders modified by alloying additions, including Ti and C. The Curie and spin reorientation temperatures of inert gas-atomized (IGA ) powders of various size fractions and annealing conditions were measured using differential thermal analysis (DTA) and SQUID AC magnetometry. The Cu rie temperatures of all size fractions of the Ti/C-containing powders are l ower for both the as-quenched and annealed portions than those of the Ti/C- free powders. The spin reorientation temperatures of the Ti/C-modified mate rial are found to be significantly lower than that expected for pure Nd2Fe1 4B. The data suggest that the alloying additions reside in the Nd2Fe14B lat tice to varying degrees, dependent upon the quench rate experienced by the particle, and are expelled from the compound to the grain boundaries upon e xtended annealing. (C) 2000 Elsevier Science S.A. All rights reserved.