Influence of mechanical stress on the microstructure of as-cast Fe-74(Nd1-xMMx)(20)B-6 alloys, MM = Brazilian misch metal

Partial replacement of neodymium by cerium-rich Brazilian misch metal, has been studied on Fe-74(Nd1-xMMx)(20)B-6 alloys by X-ray diffraction, thermom agnetic analysis, microprobe analysis and optical microscopy. Misch metal r efers 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 compou nds of Fe-74(Nd1-xMMx)(20)B-6 with x = 0.5, 0.7 and 0.9 were investigated. As-cast, pre-milled alloys present a binary microstructure with the Fe14Nd2 B 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, th e signal of the 14:2:1 phase disappears and the formation of a microstructu re is observed with a new ferromagnetic stable phase with T-c around 500 de greesC together with an increase of alpha -Fe in comparison for pre-milled samples. (C) 2001 Elsevier Science B.V. All rights reserved.