Nanocrystalline Fe-Nb-(B,Ge) alloys from ball milling: Microstructure, thermal stability and magnetic properties

Fe75B20Nb5, Fe75Ge10B10Nb5 and Fe75Ge20Nb5 alloys were prepared by ball milling from pure powders and their microstructure and magnetic properties were studied. A nanocrystalline solid solution of α-Fe type is the main phase formed, although traces of some intermetallics were found in the Fe-B-Nb alloy. The local arrangements of Fe atoms in Ge containing alloys continuously evolve with milling time. The obtained powders are thermally stable even heating up to 773 K. After heating up to 1073 K, intermetallic compounds are detected. The best soft magnetic properties are achieved after heating up to 773 K, due to stress relaxation of the nanocrystalline microstructure (for Fe-Ge-Nb alloy, coercivity ∼ 600 A/m).