Using the methods of X-ray diffraction, transmission electron microsco
py and selected area electron diffraction, five finemet alloys have be
en investigated with different chemical compositions: Fe73.5Cu1Nb3Si13
.5B9, Fe72Cu1Nb4.5Si13.5B9, Fe70.5Cu1Nb4.5Si16B8, Fe76Cu1Si13.5B9.5, a
nd Fe74Nb3Si13.5B9.5. The formation of the crystalline phases has been
studied and an attempt has been made to explain the influences of Cu
on the crystallization of the nanocrystalline phase.