Nd_2Fe_(14)B/ α-Fe nanocomposites prepared by mechanically activated disproportionation and subsequent desorption-recombination

摘要

Nd_2Fe_(14)B/α-Fe nanocomposites with a nominal composition of Nd_8Fe_(86)B_6 (atomic ratio) were prepared by mechanically activated disproportionation of the as-cast alloy via ball milling in hydrogen, and a subsequent desorption-recombination treatment of the as-milled disproportionated alloy powders. The microstructure and morphology of both the as-milled and the subsequently desorption-recombination treated powders were characterized by X-ray diffraction (XRD), magnetic force microscopy (MFM), and transmission electron microscopy (TEM). It was found that milling in hydrogen for 20h led to complete disproportionation of the Nd_2Fe_(14)B phase in the as-cast alloy into a nano-structured mixture of Nd_2H_5, FeB, and α-Fe phases with average size of no more than 10nm. After a subsequent desorption-recombination treatment at 700°C for 30min, the disproportionated alloy powders were completely turned into Nd_2Fe_(14)B/α-Fe nanocomposites with an average phase size of about 35nm, and powder size of about 130nm, respectively.