THERMOMAGNETIC STUDY OF DEVITRIFICATION IN NANOCRYSTALLINE FE(CR)SIB-CUNB ALLOYS

Structural changes taking place in the course of the amorphous to crys talline transformation in nanocrystalline Fe73.5-xCrxCu1Nb3Si13.5B9 (0 less than or equal to x less than or equal to 5) alloys were investig ated by DSC and thermomagnetic measurements. Heating up to temperature s of about 800 K leads to the formation of a nanocrystalline Fe(Si) ph ase in the amorphous matrix. The grain size is found to be in the rang e of 15-20 nm, showing no dependence on the chromium content. The comp osition of the Fe(Si) phase is estimated by the Curie temperature and a significant decrease of the silicon content in that phase, after hea ring at higher temperatures, is evidenced. After full crystallization, two main phases are detected, an Fe(Si) phase and another unknown bor ide bce phase. The effects of the chromium addition are a small increa se of the thermal stability of the amorphous alloy and a significant l owering of the Curie temperature of both the amorphous as-cast alloy a nd the final boride phase, whereas only a slight variation in T-C with composition is observed for the final Fe(Si) phase.