High Temperature Mechanical Milling as an Innovative Method for Fabrication of High Coercivity Nd-Fe-B Powders

摘要

A possibility of the application of a high temperature milling for fabrication of high-coercivity Nd-Fe-B powders was studied. Mechanical milling (milling of an ingot alloy) and mechanical alloying (milling of elementary Nd, Fe powders and a binary Fe-B alloy powder) were examined. Each of these methods was performed in two routes: (process 1) the powder was milled for a long time at room temperature, which was followed by a short milling at high temperature and (process 2) the milling was conducted continuously at high temperature. The highest coercivity showed the powders processed by mechanical milling in process 1. The coercivity of the powders processed by mechanical alloying had lower coercivity. It was observed that this parameter decreases with elongation of the milling time. This was caused by the reaction of the milled powders, mainly Nd, with the steel vial walls. The particles of Nd and Fe formed agglomerates, which finally resulted in the inhomogeneity of the final powder. It was also shown that the high temperature milling enables for fabrication of high-coercivity Nd-Fe-B powders in a single operation.