Influence of mechanical stress on the microstructure of as-cast Fe74(Nd1−xMMx)20B6 alloys, MM=Brazilian misch metal

Abstract Partial replacement of neodymium by cerium-rich Brazilian misch metal, has been studied on Fe74(Nd1−xMMx)20B6 alloys by X-ray diffraction, thermomagnetic analysis, microprobe analysis and optical microscopy. Misch metal refers to a mixture of light rare-earth metals containing 56% Ce, 18% La, 13% Nd, 05% Pr, 02% Fe and 10% others rare-earths (wt%). Intermetallic compounds of Fe74(Nd1−xMMx)20B6 with x=0.5, 0.7 and 0.9 were investigated. As-cast, pre-milled alloys present a binary microstructure with the Fe14Nd2B compound as matrix phase and Fe2MM. The amount of Fe2MM increases and the Curie temperature of the 14 : 2 : 1 compound decreases with increasing x. When these samples are submitted to 30 min of very high energy ball milling, the signal of the 14 : 2 : 1 phase disappears and the formation of a microstructure is observed with a new ferromagnetic stable phase with Tc around 500°C together with an increase of α-Fe in comparison for pre-milled samples.