The crystallization of the amorphous alloys Fe75-xCuxSi9B16 (x less than or equal to 4) is completed in three stages: (a) dendritic growth of bcc Fe[Si,Cu], (b) eutectic crystallization of bcc Fe[Si,Cu] + bet Fe3B and, finally, (c) formation of bet Fe3B. The metastable compound Fe3B formed during the second and third stages is eventually dissolved into bcc Fe and bet Fe3B. As Cu atoms replace Fe atoms, the kinetics of the whole process is modified because of microsegregation: the first stage is decelerated, the second is accelerated, and the third is accelerated up to 2 at% Cu, but is decelerated at higher concentrations.